Updated on 2026/10/07

写真a

 
SAITO Mitsuru
 
Organization
Research Field in Dentistry, Medical and Dental Sciences Area Graduate School of Medical and Dental Sciences Advanced Therapeutics Course Functional Biology and Pharmacology Professor
Title
Professor
Degree
Ph.D. (Dentistry) (2007.3 Osaka University)

Research Interests

  • Oral Physiology

  • Neurophysiology

  • 神経生理学

  • 機能系基礎歯科学

  • Neurophysiology

  • Functional Basic Dentistry

Research Areas

Neuroscience-general, Oral biological science, Neuroscience-general, Physiology, Oral biological science

Education

  • 1999.4 - 2003.3    Osaka University   Basic Dental Science Course

  • 1993.4 - 1999.3    Osaka University

  • 1990.4 - 1993.3    Osaka University   Department of Applied Chemistry

Research History

  • 2015.10    Kagoshima University   Research Field in Dentistry, Medical and Dental Sciences Area Graduate School of Medical and Dental Sciences Advanced Therapeutics Course Functional Biology and Pharmacology   Professor

  • 2015.10    Kagoshima University   Graduate School of Medical and Dental Sciences   Professor

  • 2008.4 - 2015.9    Osaka University Graduate School of Dentistry   Department of Neuroscience and Oral Physiology   Lecturer

  • 2007.4 - 2008.3    Osaka University Graduate School of Dentistry   Department of Neuroscience and Oral Physiology   Assistant Professor

  • 2003.3 - 2007.3      歯学部口腔生理学講座   助手

  • 2002.4 - 2003.2      歯学部   助手

  • 2000.4 - 2002.3      歯学部   特別研究生

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Professional Memberships

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Committee Memberships

  • 2021.4 - 2022.3    南九州歯学会   学会雑誌編集委員会 委員長   Academic society

  • 2020.4    日本顎口腔機能学会   常任理事(庶務担当)   Academic society

  • 2018.8    認知症と口腔機能研究会   基礎系世話人   Academic society

  • 2018.4 - 2020.3    日本顎口腔機能学会   理事   Academic society

  • 2016.4 - 2020.3    日本顎口腔機能学会   幹事(庶務担当)   Academic society

  • 2010.4 - 2015.9    大阪大学歯学会   評議員   Academic society

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Qualification acquired

  • Dentist

 

Papers

  • Oura N., Koyanagi-Matsumura E., Hagimoto A., Saito M., Saijo H., Miura H. .  Tamoxifen triggers a transcriptional switch from proliferation to differentiation in the circumvallate taste epithelium in mice .  Scientific Reports16 ( 1 ) 2868   2026.12

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    Language:Japanese   Publisher:Scientific Reports  

    The tamoxifen-inducible Cre-loxP system is an indispensable experimental tool in life sciences for inducing spatiotemporally controlled genetic recombination in the target tissues of living animals. The use of this technology is expected to increase in taste research. However, the direct effects of tamoxifen on taste buds remain largely unexplored. Here, we demonstrate that tamoxifen reduces cell supply to the taste buds in a dose-dependent manner. RNA sequencing of the circumvallate epithelium revealed that tamoxifen induced a transcriptional shift from proliferation to differentiation. The genes regulating the cell cycle were downregulated, whereas genes promoting the differentiation of epithelial cells and keratinocytes were upregulated. Within taste buds, Shh was downregulated in immature precursor cells, whereas cell type-specific genes were broadly upregulated in mature taste bud cells. Notably, transcription factors driving taste cell type differentiation, such as Pou2f3, Ascl1, and Nkx2-2, were induced, suggesting that tamoxifen activates transcription to promote the differentiation of all cell types in taste buds, rather than activating particular signaling pathways in specific cell types. These findings indicate that tamoxifen rapidly triggers a transcriptional switch from proliferation to differentiation in the circumvallate taste epithelium, highlighting a potential confounding effect in taste research that employs tamoxifen administration.

    DOI: 10.1038/s41598-025-32701-8

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  • Hagimoto A., Koyanagi-Matsumura E., Oura N., Saito M., Tanaka T., Miura H. .  Prox1 maintains taste bud structure via inhibition of apoptosis .  Cell and Tissue Research403 ( 2 ) 16   2026.2

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    Language:Japanese   Publisher:Cell and Tissue Research  

    Taste buds are maintained by continuous cell renewal, receiving a steady influx of postmitotic cells from the surrounding epithelial region. Within taste buds, Type I, II, and III cells continuously differentiate from Type IV postmitotic precursor cells and are removed via apoptosis. These processes are likely governed by various transcription factors. Among the transcription factors expressed in taste buds, Prox1, a homeobox transcription factor, is the only factor expressed in all taste bud cells including precursor cells. However, its role in taste buds remains unclear. Here, we investigate the function of Prox1 in taste bud cell turnover using conditional knockout (cKO) mice. In Prox1 cKO mice, all Type I, II, and III cells were significantly reduced, resulting in approximately half the total cell number per taste bud compared to wild-type mice, while Type IV cell numbers remained comparable. Apoptosis of taste bud cells nearly doubled, leading to a shortened lifespan of taste bud cells. EdU pulse-labeling experiments revealed a biphasic decline in EdU(+) taste bud cells in Prox1 cKO mice, indicating that Prox1 knockout increases the fraction of cells that die shortly after differentiating into taste bud cells. The surviving cells still exhibited a shorter lifespan than that of wild-type mice. We also observed previously unreported structural alterations within taste buds caused by enhanced apoptosis using whole-mount analysis. These results demonstrate that Prox1 contributes to the maintenance of taste bud structure by regulating the lifespan of taste bud cells, highlighting its essential role in taste bud homeostasis.

    DOI: 10.1007/s00441-025-04040-7

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  • Youngnam Kang, Mitsuru Saito, Hiroki Toyoda .  Molecular, Morphological and Electrophysiological Differences between Alpha and Gamma Motoneurons with Special Reference to the Trigeminal Motor Nucleus of Rat. .  International journal of molecular sciences25 ( 10 )   2024.5International journal

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    Language:English   Publishing type:Research paper (scientific journal)  

    The muscle contraction during voluntary movement is controlled by activities of alpha- and gamma-motoneurons (αMNs and γMNs, respectively). In spite of the recent advances in research on molecular markers that can distinguish between αMNs and γMNs, electrophysiological membrane properties and firing patterns of γMNs have remained unknown, while those of αMNs have been clarified in detail. Because of the larger size of αMNs compared to γMNs, blindly or even visually recorded MNs were mostly αMNs, as demonstrated with molecular markers recently. Subsequently, the research on αMNs has made great progress in classifying their subtypes based on the molecular markers and electrophysiological membrane properties, whereas only a few studies demonstrated the electrophysiological membrane properties of γMNs. In this review article, we provide an overview of the recent advances in research on the classification of αMNs and γMNs based on molecular markers and electrophysiological membrane properties, and discuss their functional implication and significance in motor control.

    DOI: 10.3390/ijms25105266

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  • Youngnam Kang, Hiroki Toyoda, Mitsuru Saito .  Search for unknown neural link between the masticatory and cognitive brain systems to clarify the involvement of its impairment in the pathogenesis of Alzheimer's disease. .  Frontiers in cellular neuroscience18   1425645 - 1425645   2024International journal

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    Brain degenerations in sporadic Alzheimer's disease (AD) are observed earliest in the locus coeruleus (LC), a population of noradrenergic neurons, in which hyperphosphorylated tau protein expression and β-amyloid (Aβ) accumulation begin. Along with this, similar changes occur in the basal forebrain cholinergic neurons, such as the nucleus basalis of Meynert. Neuronal degeneration of the two neuronal nuclei leads to a decrease in neurotrophic factors such as brain-derived neurotrophic factor (BDNF) in the hippocampus and cerebral cortex, which results in the accumulation of Aβ and hyperphosphorylated tau protein and ultimately causes neuronal cell death in those cortices. On the other hand, a large number of epidemiological studies have shown that tooth loss or masticatory dysfunction is a risk factor for dementia including AD, and numerous studies using experimental animals have also shown that masticatory dysfunction causes brain degeneration in the basal forebrain, hippocampus, and cerebral cortex similar to those observed in human AD, and that learning and memory functions are impaired accordingly. However, it remains unclear how masticatory dysfunction can induce such brain degeneration similar to AD, and the neural mechanism linking the trigeminal nervous system responsible for mastication and the cognitive and memory brain system remains unknown. In this review paper, we provide clues to the search for such "missing link" by discussing the embryological, anatomical, and physiological relationship between LC and its laterally adjoining mesencephalic trigeminal nucleus which plays a central role in the masticatory functions.

    DOI: 10.3389/fncel.2024.1425645

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  • Toyoda H, Fujinami Y, Saito M, Maeda Y, Kang Y .  Increased vertical dimension of occlusion for varying periods differentially impairs learning and memory in guinea pigs .  Behavioural Brain Research452   114547 - 114547   2023.6Reviewed International journal

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    Language:English   Publishing type:Research paper (scientific journal)  

    There is an increasing number of studies showing that occlusal dysfunction impairs learning and memory. We previously demonstrated that the brain has a mechanism to calibrate between the activities of spindle afferents and periodontal-mechanoreceptor afferents for controlling the chewing movement, and the accurate calibration can be done only at the proper vertical dimension of occlusion (VDO). Then, the chewing at an inappropriate VDO may induce a severe mental stress due to a mal-calibration. However, it is not clear how the impairment of learning/memory progresses over the period of stress induced by occlusal dysfunction. We investigated by passive avoidance test how the behavior and learning/memory are altered in guinea pigs in which the VDO was raised by 2-3 mm over the period up to 8 weeks. We found that the guinea pigs reared under the raised occlusal-condition (ROC) for 1 week showed a very high sensitivity to electrical stimulation whereas this did not cause the memory consolidation in the 1st-day retention trial, suggesting that such hypersensitivity rather hampered the fear learning. In the guinea pigs reared under the ROC for 2 and 8 weeks, the learning ability was not largely affected and memory consolidation occurred similarly whereas the memory retention deteriorated more severely in the latter guinea pigs than in the former ones. In the guinea pigs reared under the ROC for 3 and 4 weeks, learning was severely impaired, and memory consolidation did not occur. These results suggest that the occlusal dysfunction for varying periods differentially impairs learning and memory.

    DOI: 10.1016/j.bbr.2023.114547

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  • Tanaka Y, Sato H, Toyoda H, Saito M, Maeda Y, Kang Y .  The mechanism for regulating the isometric contraction of masseter muscles is involved in determining the vertical dimension of occlusion .  Journal of Neurophysiology129 ( 1 ) 211 - 219   2023.1Reviewed

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:American Physiological Society  

    We previously demonstrated that accurate regulation of isometric contraction (IC) of jaw-closing muscles to counteract the ramp load applied to the jaw in the jaw-opening direction is achieved through the calibration between the two sensations arising from muscle spindles (MSs) and periodontal mechanoreceptors (PMRs). However, it remains unclear whether this calibration mechanism accurately works at any jaw positions, i.e., any vertical dimensions of occlusion (VDO). In the present study, we examined the effects of altering VDO on the IC of the masseter muscles in complete dentulous and edentulous subjects. At a VDO higher than the original VDO (O-VDO), the root mean square (RMS) of masseter EMG activity increased more steeply with a load increase, resulting in an over-counteraction. The regression coefficient of the Load-RMS relationship significantly increased as the VDO was increased, suggesting that the overestimation became more pronounced with the VDO increases. Consistently also in the edentulous subjects, at a higher VDO than the O-VDO, a steeper increase in the RMS emerged with a delay in response to the same ramp load while a similar steeper increase was seen surprisingly even at a lower VDO. Thus, the edentulous subjects displayed a delayed overestimation of the ramp load presumably due to less and slowly sensitive mucous membrane mechanoreceptor (MMR) in alveolar ridge compared to the PMR. Taken together, the accurate calibration between the two sensations arising from MSs and PMRs/MMRs can be done only at the O-VDO, suggesting that the O-VDO is the best calibration point for performing accurate IC.

    DOI: 10.1152/jn.00301.2022

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  • Saito M, Tanaka C, Toyoda H, Kang Y .  Subcellular localization of homomeric TASK3 channels and its presumed functional significances in trigeminal motoneurons .  International Journal of Molecular Sciences24 ( 1 ) 344 - 344   2022.12Reviewed

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    Authorship:Lead author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:MDPI AG  

    Somatic expressions of either heteromeric TASK1/3 or homomeric TASK1/1 channels have been reported in various neurons, while expression of homomeric TASK3/3 channels has been re-ported only in dendrites. However, it is not known why homomeric TASK3/3 channels are hardly seen in somata of CNS neurons. Given the absence of somatic TASK3/3 channels, it should be clarified why dendritic expression of TASK3/3 channels is inevitable and necessary and how differentially distributed TASK1/1 and TASK3/3 channels play roles in soma-to-dendritic integration. Here, we addressed these questions. We found that TASK3-transfected HEK293 cells showed decreases in cell volume after being transferred from the cultured medium to HEPES Ringer, suggesting that expressions of TASK3 channels in cell bodies cause an osmolarity problem. Using TASK1- and TASK3-transfected oocytes, we also found that cGMP application slightly suppressed TASK3 currents while it largely enhanced TASK1 currents, alleviating the difference between TASK1 and TASK3 currents at physiological pH. As larger motoneurons have extensive dendritic trees while smaller motoneurons have poor ones, cGMP could integrate Ia-EPSPs to recruit small and large motoneurons synchronously by differentially modulating TASKI and TASK3 channels which were complementary distributed in soma and dendrites of motoneurons in the dorsolateral part of the trigeminal motor nucleus.

    DOI: 10.3390/ijms24010344

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  • Hiroki Toyoda, Jonghwa Won, Wheedong Kim, Hayun Kim, Oscar Davy, Mitsuru Saito, Doyun Kim, Takuma Tanaka, Youngnam Kang, Seog Bae Oh .  The Nature of Noradrenergic Volume Transmission From Locus Coeruleus to Brainstem Mesencephalic Trigeminal Sensory Neurons .  Frontiers in Cellular Neuroscience16   841239 - 841239   2022.4Reviewed International coauthorship International journal

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Frontiers Research Foundation  

    Noradrenergic neurons in the locus coeruleus (LC) release noradrenaline (NA) that acts via volume transmission to activate extrasynaptic G-protein coupled receptors (GPCRs) in target cells throughout the brain. As the closest projection, the dorsal LC laterally adjoins the mesencephalic trigeminal nucleus (MTN), in which proprioceptive primary sensory neurons innervating muscle spindles of jaw-closing muscles are exceptionally located. MTN neurons express α2-adrenergic receptors (α2-ARs) and display hyperpolarization-activated cyclic nucleotide-gated (HCN) currents (Ihs), which is downregulated by α2-AR activation. To quantify the activity-dependent outcome of volume transmission of NA from LC to MTN, we investigated how direct LC activation inhibits Ih in MTN neurons by performing dual whole-cell recordings from LC and MTN neurons. Repetition of 20 Hz spike-train evoked with 1-s current-pulse in LC neurons every 30 s resulted in a gradual decrease in Ih evoked every 30 s, revealing a Hill-type relationship between the number of spike-trains in LC neurons and the degree of Ih inhibition in MTN neurons. On the other hand, when microstimulation was applied in LC every 30 s, an LC neuron repeatedly displayed a transient higher-frequency firing followed by a tonic firing at 5-10 Hz for 30 s. This subsequently caused a similar Hill-type inhibition of Ih in the simultaneously recorded MTN neuron, but with a smaller Hill coefficient, suggesting a lower signal transduction efficacy. In contrast, 20 Hz activity induced by a 1-s pulse applied every 5-10 s caused only a transient facilitation of Ih inhibition followed by a forced termination of Ih inhibition. Thus, the three modes of LC activities modulated the volume transmission to activate alpha2-adrenergic GPCR to differentially inhibit Ih in MTN neurons.

    DOI: 10.3389/fncel.2022.841239

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  • Koyanagi-Matsumura E, Miura H, Saito M, Harada S .  Type II/III cell composition and NCAM expression in taste buds .  Cell Tissue Research385 ( 3 ) 557 - 570   2021.9Reviewed

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    DOI: 10.1007/s00441-021-03452-5

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  • 小柳 江梨子[松村], 三浦 裕仁, 齋藤 充, 原田 秀逸 .  成マウスの有郭乳頭における味蕾に関連した線維芽細胞増殖因子の発現(Taste bud-associated expression of fibroblast growth factors in the circumvallate papillae in adult mice) .  南九州歯学会雑誌2 ( 1 ) 1 - 11   2021.3

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    【目的】本研究は,成マウスの味蕾で特異的に発現する線維芽細胞増殖因子(Fgf)とその受容体(Fgfr)を見いだし,発現パターンを明らかにすることを目的とした.【方法】2つの舌上皮領域:1)味蕾を含む味覚上皮として有郭・葉状乳頭,2)味蕾を含まない非味覚上皮として舌中央部からトータルRNAを抽出した.全てのFgfとFgfrファミリー分子のRT-PCRを行って味覚上皮と非味覚上皮の間で比較し,味覚上皮で強く発現する分子を明らかにした.さらに,有郭乳頭の凍結切片でin situハイブリダイゼーションを行い、味蕾付近の発現パターンを解析した.in situハイブリダーゼーションと同時に,Kcnq1の免疫組織化学を行って味蕾の輪郭を可視化し,Fgfの発現が味蕾の内部であるか外側であるかを判別した.【結果】RT-PCRにより,22種のFgfのうちFgf1,9,13,14,20が,非味覚上皮よりも味覚上皮に強く発現することが示された.in situハイブリダイゼーションにより,Fgf1,13,14は味蕾に関連した発現が明らかになった.Fgf1は,殆どすべての味蕾細胞と味蕾近傍に強く発現していた.Fgf13,14は,一部の味蕾細胞に強く発現していた.一方,Fgf9,20は舌上皮に広く発現していた.【結論】Fgf1,13,14は味蕾に関連して発現しており,味蕾のホメオスタシスと機能に関与すると考えられる.(著者抄録)

  • Kang Y, Saito M, Toyoda H .  Molecular and Regulatory Mechanisms of Desensitization and Resensitization of GABAA Receptors with a Special Reference to Propofol/Barbiturate .  International Journal of Molecular Sciences21 ( 2 ) 563   2020.1Reviewed International journal

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Basel  

    It is known that desensitization of GABAA receptor (GABAAR)-mediated currents is paradoxically correlated with the slowdown of their deactivation, i.e., resensitization. It has been shown that an upregulation of calcineurin enhances the desensitization of GABAAR-mediated currents but paradoxically prolongs the decay phase of inhibitory postsynaptic currents/potentials without appreciable diminution of their amplitudes. The paradoxical correlation between desensitization and resensitization of GABAAR-mediated currents can be more clearly seen in response to a prolonged application of GABA to allow more desensitization, instead of brief pulse used in previous studies. Indeed, hump-like GABAAR currents were produced after a strong desensitization at the offset of a prolonged puff application of GABA in pyramidal cells of the barrel cortex, in which calcineurin activity was enhanced by deleting phospholipase C-related catalytically inactive proteins to enhance the desensitization/resensitization of GABAAR-mediated currents. Hump-like GABAAR currents were also evoked at the offset of propofol or barbiturate applications in hippocampal or sensory neurons, but not GABA applications. Propofol and barbiturate are useful to treat benzodiazepine/alcohol withdrawal syndrome, suggesting that regulatory mechanisms of desensitization/resensitization of GABAAR-mediated currents are important in understanding benzodiazepine/alcohol withdrawal syndrome. In this review, we will discuss the molecular and regulatory mechanisms underlying the desensitization and resensitization of GABAAR-mediated currents and their functional significances.

    DOI: 10.3390/ijms21020563

  • Kawasaki Y, Saito M, Won J, Bae JY, Sato H, Toyoda H, Kuramoto E, Kogo M, Tanaka T, Kaneko T, Oh SB, Bae YC, Kang Y .  Inhibition of GluR Current in Microvilli of Sensory Neurons via Na+-Microdomain Coupling Among GluR, HCN Channel, and Na+/K+ Pump .  Frontiers in Cellular Neuroscience12   113   2018.4Reviewed

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Frontiers Research Foundation  

    Glutamatergic dendritic EPSPs evoked in cortical pyramidal neurons are depressed by activation of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels expressed in dendritic spines. This depression has been attributed to shunting effects of HCN current (Ih) on input resistance or Ih deactivation. Primary sensory neurons in the rat mesencephalic trigeminal nucleus (MTN) have the somata covered by spine-like microvilli that express HCN channels. In rat MTN neurons, we demonstrated that Ih enhancement apparently diminished the glutamate receptor (GluR) current (IGluR) evoked by puff application of glutamate/AMPA and enhanced a transient outward current following IGluR (OT-IGluR). This suggests that some outward current opposes inward IGluR. The IGluR inhibition displayed a U-shaped voltage-dependence with a minimal inhibition around the resting membrane potential, suggesting that simple shunting effects or deactivation of Ih cannot explain the U-shaped voltage-dependence. Confocal imaging of Na+ revealed that GluR activation caused an accumulation of Na+ in the microvilli, which can cause a negative shift of the reversal potential for Ih (Eh). Taken together, it was suggested that IGluR evoked in MTN neurons is opposed by a transient decrease or increase in standing inward or outward Ih, respectively, both of which can be caused by negative shifts of Eh, as consistent with the U-shaped voltage-dependence of the IGluR inhibition and the OT-IGluR generation. An electron-microscopic immunohistochemical study revealed the colocalization of HCN channels and glutamatergic synapses in microvilli of MTN neurons, which would provide a morphological basis for the functional interaction between HCN and GluR channels. Mathematical modeling eliminated the possibilities of the involvements of Ih deactivation and/or shunting effect and supported the negative shift of Eh which causes the U-shaped voltage-dependent inhibition of IGluR.

    DOI: 10.3389/fncel.2018.00113

    Other Link: https://www.frontiersin.org/articles/10.3389/fncel.2018.00113/full

  • Nishimura K, Ohta M, Saito M, Morita-Isogai Y, Sato H, Kuramoto E, Yin DX, Maeda Y, Kaneko T, Yamashiro T, Takada K, Oh SB, Toyoda H, Kang Y .  Electrophysiological and Morphological Properties of α and γ Motoneurons in the Rat Trigeminal Motor Nucleus .  Frontiers in Cellular Neuroscience12   9   2018.1Reviewed

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Frontiers Research Foundation  

    The muscle contraction during voluntary movement is regulated by activities of α- and γ-motoneurons (αMNs and γMNs, respectively). The tension of jaw-closing muscles can be finely tuned over a wide range. This excellent function is likely to be achieved by the specific populations of αMNs innervating jaw-closing muscles. Indeed, we have recently demonstrated that in the rat dorsolateral trigeminal motor nucleus (dl-TMN), the size distribution of αMNs was bimodal and the population of smaller αMNs showed a size distribution similar to that of γMNs, by immunohistochemically identifying αMNs and γMNs based on the expressions of estrogen-related receptor gamma (Err3) and neuronal DNA binding protein NeuN together with ChAT. This finding suggests the presence of αMNs as small as γMNs. However, differences in the electrophysiological membrane properties between αMNs and γMNs remain unknown also in the dl-TMN. Therefore, in the present study, we studied the electrophysiological membrane properties of MNs in the dl-TMN of infant rats at postnatal days 7-12 together with their morphological properties using whole-cell current-clamp recordings followed by immunohistochemical staining with an anti-NeuN and anti-ChAT antibodies. We found that the ChAT-positive and NeuN-positive αMNs were divided into two subclasses: the first one had a larger cell body and displayed a 4-aminopyridine (4-AP)-sensitive current while the second one had a smaller cell body and displayed a less prominent 4-AP-sensitive current and a low-threshold spike, suitable for their orderly recruitment. We finally found that γMNs showing ChAT-positive and NeuN-negative immunoreactivities had smaller cell bodies and displayed an afterdepolarization mediated by flufenamate-sensitive cation current. It is suggested that these electrophysiological and morphological features of MNs in the dl-TMN are well correlated with the precise control of occlusion.

    DOI: 10.3389/fncel.2018.00009

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  • Morita-Isogai Y, Sato H, Saito M, Kuramoto E, Yin DX, Kaneko T, Yamashiro T, Takada K, Oh SB, Toyoda H, Kang Y .  A distinct functional distribution of α and γ motoneurons in the rat trigeminal motor nucleus .  Brain Structure and Function222 ( 7 ) 3231 - 3239   2017.9Reviewed

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Springer-Verlag  

    γ-motoneurons (γMNs) play a crucial role in regulating isometric muscle contraction. The slow jaw-closing during mastication is one of the most functional isometric contractions, which is developed by the rank-order recruitment of α-motoneurons (αMNs) in a manner that reflects the size distribution of αMNs. In a mouse spinal motor nucleus, there are two populations of small and large MNs; the former was identified as a population of γMNs based on the positive expression of the transcription factor estrogen-related receptor 3 (Err3) and negative expression of the neuronal DNA-binding protein NeuN, and the latter as that of αMNs based on the opposite pattern of immunoreactivity. However, the differential identification of αMNs and γMNs in the trigeminal motor nucleus (TMN) remains an assumption based on the size of cell bodies that were retrogradely stained with HRP. We here examined the size distributions of αMNs and γMNs in the dorsolateral TMN (dl-TMN) by performing immunohistochemistry using anti-Err3 and anti-NeuN antibodies. The dl-TMN was identified by immunopositivity for vesicular glutamate transporter-1. Immunostaining for choline acetyltransferase and Err3/NeuN revealed that the dl-TMN is composed of 65% αMNs and 35% γMNs. The size distribution of αMNs was bimodal, while that of γMNs was almost the same as that of the population of small αMNs, suggesting the presence of αMNs as small as γMNs. Consistent with the size concept of motor units, the presence of smaller jaw-closing αMNs was coherent with the inclusion of jaw-closing muscle fibers with smaller diameters compared to limb muscle fibers.

    DOI: 10.1007/s00429-017-1400-8

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  • Kang Y, Sato H, Saito M, Yin DX, Park SK, Oh SB, Bae YC, Toyoda H .  A role of CB1R in inducing theta-rhythm coordination between the gustatory and gastrointestinal insula .  Scientific Reports6   32529   2016.9Reviewed

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Nature Publishing Group  

    Anandamide (AEA) and N-oleoylethanolamine (OEA) are produced in the intestine and brain during fasting and satiety, respectively. Subsequently, AEA facilitates food intake via activation of cannabinoid type-1 receptors (CB1Rs) while OEA decreases food intake via activation of peroxisome proliferator-activated receptor-alpha (PPARalpha) and/or G-protein-coupled receptor 119 (GPR119). Neuronal activity in the gastrointestinal region of the autonomic insula (GI-Au-I) that rostrally adjoins the gustatory insula (Gu-I) increases during fasting, enhancing appetite while umami and sweet taste sensations in Gu-I enhances appetite in GI-Au-I, strongly suggesting the presence of a neural interaction between the Gu-I and GI-Au-I which changes depending on the concentrations of AEA and OEA. However, this possibility has never been investigated. In rat slice preparations, we demonstrate with voltage-sensitive dye imaging that activation of CB1Rs by AEA induces theta-rhythm oscillatory synchronization in the Gu-I which propagates into the GI-Au-I but stops at its caudal end, displaying an oscillatory coordination. The AEA-induced oscillation was abolished by a CB1R antagonist or OEA through activation of GPR119. Our results demonstrate that the neural coordination between the Gu-I and GI-Au-I is generated or suppressed by the opposing activities between CB1R and GPR119. This mechanism may be involved in the feeding behavior based on taste recognition.

    DOI: 10.1038/srep32529

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  • Okamoto K, Emura N, Sato H, Fukatsu Y, Saito M, Tanaka C, Morita Y, Nishimura K, Kuramoto E, Yin DX, Furutani K, Okazawa M, Kurachi Y, Kaneko T, Maeda Y, Yamashiro T, Takada K, Toyoda H, Kang Y .  The possible role of TASK channels in rank-ordered recruitment of motoneurons in the dorsolateral part of the trigeminal motor nucleus .  eNeuro3 ( 3 ) ENEURO.0138-16.2016   2016.5Reviewed

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Society for Neuroscience  

    Because a rank-ordered recruitment of motor units occurs during isometric contraction of jaw-closing muscles, jaw-closing motoneurons (MNs) may be recruited in a manner dependent on their soma sizes or input resistances (IRs). In the dorsolateral part of the trigeminal motor nucleus (dl-TMN) in rats, MNs abundantly express TWIK (two-pore domain weak inwardly rectifying K channel)-related acid-sensitive-K+ channel (TASK)-1 and TASK3 channels, which determine the IR and resting membrane potential. Here we examined how TASK channels are involved in IR-dependent activation/recruitment of MNs in the rat dl-TMN by using multiple methods. The real-time PCR study revealed that single large MNs (>35 microm) expressed TASK1 and TASK3 mRNAs more abundantly compared with single small MNs (15-20 microm). The immunohistochemistry revealed that TASK1 and TASK3 channels were complementarily distributed in somata and dendrites of MNs, respectively. The density of TASK1 channels seemed to increase with a decrease in soma diameter while there were inverse relationships between the soma size of MNs and IR, resting membrane potential, or spike threshold. Dual whole-cell recordings obtained from smaller and larger MNs revealed that the recruitment of MNs depends on their IRs in response to repetitive stimulation of the presumed Ia afferents. 8-Bromoguanosine-cGMP decreased IRs in small MNs, while it hardly changed those in large MNs, and subsequently decreased the difference in spike-onset latency between the smaller and larger MNs, causing a synchronous activation of MNs. These results suggest that TASK channels play critical roles in rank-ordered recruitment of MNs in the dl-TMN.

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  • Kawakami S, Sato H, Sasaki AT, Tanabe HC, Yoshida Y, Saito M, Toyoda H, Sadato N, Kang Y .  The brain mechanisms underlying the perception of pungent taste of capsaicin and the subsequent autonomic responses .  Frontiers in Human Neuroscience9   720   2016.1Reviewed

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    In a human fMRI study, it has been demonstrated that tasting and ingesting capsaicin activate the ventral part of the middle and posterior short gyri (M/PSG) of the insula which is known as the primary gustatory area, suggesting that capsaicin is recognized as a taste. Tasting and digesting spicy foods containing capsaicin induce various physiological responses such as perspiration from face, salivation, and facilitation of cardiovascular activity, which are thought to be caused through viscero-visceral autonomic reflexes. However, this does not necessarily exclude the possibility of the involvement of higher-order sensory-motor integration between the M/PSG and anterior short gyrus (ASG) known as the autonomic region of the insula. To reveal a possible functional coordination between the M/PSG and ASG, we here addressed whether capsaicin increases neural activity in the ASG as well as the M/PSG using fMRI and a custom-made taste delivery system. Twenty subjects participated in this study, and three tastant solutions: capsaicin, NaCl, and artificial saliva (AS) were used. Group analyses with the regions activated by capsaicin revealed significant activations in the bilateral ASG and M/PSG. The fMRI blood oxygenation level-dependent (BOLD) signals in response to capsaicin stimulation were significantly higher in ASG than in M/PSG regardless of the side. Concomitantly, capsaicin increased the fingertip temperature significantly. Although there was no significant correlation between the fingertip temperatures and BOLD signals in the ASG or M/PSG when the contrast [Capsaicin AS] or [Capsaicin NaCl] was computed, a significant correlation was found in the bilateral ASG when the contrast [2 x Capsaicin-NaCl-AS] was computed. In contrast, there was a significant correlation in the hypothalamus regardless of the contrasts. Furthermore, there was a significant correlation between M/PSG and ASG. These results indicate that capsaicin increases neural activity in the ASG as well as the M/PSG, suggesting that the neural coordination between the two cortical areas may be involved in autonomic responses to tasting spicy foods as reflected in fingertip temperature increases.

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  • Toyoda H, Saito M, Sato H, Kawano T, Kawakami S, Yatani H, Kanematsu T, Hirata M, Kang Y .  Enhanced lateral inhibition in the barrel cortex by deletion of phospholipase C-related catalytically inactive protein-1/2 in mice .  Pflügers Archiv - European Journal of Physiology467 ( 7 ) 1445 - 1456   2015.7Reviewed

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    We previously demonstrated that the deletion of phospholipase C-related catalytically inactive protein-1/2 (PRIP-1/2) enhances the desensitization of GABAA receptors (GABAARs), while it facilitates their resensitization at the offset of GABA puff, causing a hump-like tail current (tail-I) in layer 3 (L3) pyramidal cells (PCs) of the barrel cortex. In the present study, we investigated whether inhibitory synaptic transmission in L3 PCs in the barrel cortex is altered in the PRIP-1/2 double-knockout (PRIP-DKO) mice, and if so, how the interaction between excitation and inhibition is subsequently modified. PRIP-1/2 deletion resulted in the prolongation of the decay phase of inhibitory postsynaptic currents/potentials (IPSCs/IPSPs) in L3 PCs evoked by stimulation of L3, leaving the overall features of miniature IPSCs unchanged. An optical imaging revealed that the spatiotemporal profile of a horizontal excitation spread across columns in L2/3 caused by L4 stimulation in the barrel cortex was more restricted in PRIP-DKO mice compared to the wild type, while those obtained in the presence of bicuculline were almost identical between the two genotypes. These findings suggest that PRIP-1/2 deletion enhances the lateral inhibition by prolonging inhibitory synaptic actions to limit the intercolumnar integration in the barrel cortex. Considering the present findings together with our previous study including a mathematical simulation, the prolongation of inhibitory synaptic actions is likely to result from an enhancement of desensitization followed by an enhanced resensitization in GABAARs.

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  • Chung G, Saito M, Kawasaki Y, Kawano T, Yin D, Lee S, Kogo M, Takada M, Bae YC, Kim JS, Oh SB, Kang Y .  Generation of resonance-dependent oscillation by mGluR-I activation switches single spiking to bursting in mesencephalic trigeminal sensory neurons .  The European Journal of Neuroscience41 ( 8 ) 998 - 1012   2015.4Reviewed

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    The primary sensory neurons supplying muscle spindles of jaw-closing muscles are unique in that they have their somata in the mesencephalic trigeminal nucleus (MTN) in the brainstem, thereby receiving various synaptic inputs. MTN neurons display bursting upon activation of glutamatergic synaptic inputs while they faithfully relay respective impulses arising from peripheral sensory organs. The persistent sodium current (INaP) is reported to be responsible for both the generation of bursts and the relay of impulses. We addressed how INaP is controlled either to trigger bursts or to relay respective impulses as single spikes in MTN neurons. Protein kinase C (PKC) activation enhanced INaP only at low voltages. Spike generation was facilitated by PKC activation at membrane potentials more depolarized than the resting potential. By injection of a ramp current pulse, a burst of spikes was triggered from a depolarized membrane potential whereas its instantaneous spike frequency remained almost constant despite the ramp increases in the current intensity beyond the threshold. A puff application of glutamate preceding the ramp pulse lowered the threshold for evoking bursts by ramp pulses while chelerythrine abolished such effects of glutamate. Dihydroxyphenylglycine, an agonist of mGluR1/5, also caused similar effects, and increased both the frequency and impedance of membrane resonance. Immunohistochemistry revealed that glutamatergic synapses are made onto the stem axons, and that mGluR1/5 and Nav1.6 are co-localized in the stem axon. Taken together, glutamatergic synaptic inputs onto the stem axon may be able to switch the relaying to the bursting mode.

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  • Toyoda H, Saito M, Sato H, Tanaka T, Ogawa T, Yatani H, Kawano T, Kanematsu T, Hirata M, Kang Y .  Enhanced desensitization followed by unusual resensitization in GABAA receptors in phospholipase C-related catalytically inactive protein-1/2 double-knockout mice .  Pflügers Archiv - European Journal of Physiology467 ( 2 ) 267 - 285   2015.2Reviewed

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    Phospholipase C-related catalytically inactive proteins (PRIP-1/2) are previously reported to be involved in the membrane trafficking of GABAA receptor (GABAAR) and the regulation of intracellular Ca2+ stores. GABAAR-mediated currents can be regulated by the intracellular Ca2+. However, in PRIP-1/2 double-knockout (PRIP-DKO) mice, it remains unclear whether the kinetic properties of GABAARs are modulated by the altered regulation of intracellular Ca2+ stores. Here, we investigated whether GABAAR currents (IGABA) evoked by GABA puff in layer 3 (L3) pyramidal cells (PCs) of the barrel cortex are altered in PRIP-DKO mice. The deletion of PRIP-1/2 enhanced the desensitization of IGABA but induced a hump-like tail current (tail-I) at the GABA puff offset. IGABA and the hump-like tail-I were suppressed by GABAAR antagonists. The enhanced desensitization of IGABA and the hump-like tail-I in PRIP-DKO PCs were mediated by increases in the intracellular Ca2+ concentration and were largely abolished by a calcineurin inhibitor and ruthenium red. Calcium imaging revealed that Ca2+-induced Ca2+ release (CICR) and subsequent store-operated Ca2+ entry (SOCE) are more potent in PRIP-DKO PCs than in wild-type PCs. A mathematical model revealed that a slowdown of GABA-unbinding rate and an acceleration of fast desensitization rate by enhancing its GABA concentration dependency are involved in the generation of hump-like tail-Is. These results suggest that in L3 PCs of the barrel cortex in PRIP-DKO mice, the increased calcineurin activity due to the potentiated CICR and SOCE enhances the desensitization of GABAARs and slows the GABA-unbinding rate, resulting in their unusual resensitization following removal of GABA.

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  • Sato H, Kawano T, Saito M, Toyoda H, Maeda Y, Türker KS, Kang Y .  Teeth clenching reduces arm abduction force .  Experimental Brain Research232 ( 7 ) 2281 - 2291   2014.7Reviewed

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    It has been reported that the 90-deg arm abduction force counteracting external adduction loads appeared to be smaller under teeth clenching condition than under non-clenching condition. To elucidate the physiological mechanism underlying the possible inhibitory effect of teeth clenching on the arm abduction, we have attempted to quantify the difference in the force induced against the fast and slow ramp load between the arm abductions under teeth non-clenching and clenching conditions. When the load of adduction moment was linearly increased, the abductor force increased to a maximal isometric contraction force (MICF) and further increased to a maximal eccentric contraction force (MECF) with forced adduction. The MICF measured under teeth clenching was significantly lower than that under non-clenching, despite no significant difference in the MECF between the two conditions. The reduction in MICF caused by teeth clenching was enhanced by increasing the velocity of the load. These results suggest that clenching inhibits abduction force only during isometric contraction phase. The invariability of MECF would indicate the lack of involvement of fatigue in such inhibitory effects of clenching. To discover the source of the inhibition, we have examined the effects of teeth clenching on the stretch reflex in the deltoid muscle. The stretch reflex of deltoid muscles was inhibited during clenching, contrary to what was expected from the Jendrassik maneuver. Taken together, our results suggest that the teeth clenching reduced the MICF by depressing the recruitment of deltoid motoneurones presumably via the presynaptic inhibition of spindle afferent inputs onto those motoneurones.

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  • Saito M, Tanaka T, Sato H, Toyoda H, Aoyagi T, Kang Y .  A mathematical model of negative covariability of inter-columnar excitatory synaptic actions caused by presynaptic inhibition .  The European Journal of Neuroscience38 ( 7 ) 2999 - 3007   2013.10Reviewed

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    We previously showed that a positive covariability between intracortical excitatory synaptic actions onto the two layer three pyramidal cells (PCs) located in mutually adjacent columns is changed into a negative covariability by column-wise presynaptic inhibition of intracortical inputs, implicated as a basis for the desynchronization of inter-columnar synaptic actions. Here we investigated how the inter-columnar desynchronization is modulated by the strength of presynaptic inhibition or other factors, by using a mathematical model. Based on our previous findings on the paired-pulse depression (PPD) of intracortical excitatory postsynaptic currents (EPSCs) evoked in PCs located in the stimulated home column (HC) but no PPD in PCs located in the adjacent column (AC), a mathematical model of synaptic connections between PCs and inhibitory interneurons was constructed. When the paired-pulse ratio (PPR) was decreased beyond 0.80, the correlation coefficient between the two second EPSC amplitudes in the paired PCs located in the HC and AC and that in the paired PCs located in the same HC exhibited opposite changes, and reached a global negative maximum and local positive maximum, respectively, at almost the same PPR (0.40). At this PPR, the desynchronization between the two cell assemblies in mutually adjacent columns would be maximized. These positive and negative covariabilities were not produced without background oscillatory synchronization across columns and were enhanced by increasing the synchronization magnitude, indicating that the synchronization leads to the desynchronization. We propose that a slow oscillatory synchronization across columns may emerge following the liberation from the column-wise presynaptic inhibition of inter-columnar synaptic inputs.

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  • Sato H, Toyoda H, Saito M, Kobayashi M, Althof D, Kulik A, Kang Y .  GABAB receptor-mediated presynaptic inhibition reverses inter-columnar covariability of synaptic actions by intracortical axons in the rat barrel cortex .  The European Journal of Neuroscience37 ( 2 ) 190 - 202   2013.1Reviewed

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    Intracortical axons originating from pyramidal cells in layer 3 of the rat somatosensory cortex are shared between adjacent columns, and receive the presynaptic inhibition that is mediated by the GABAB receptor. Synaptic actions by intracortical axons of single layer 3 pyramidal cells covary between the two adjacent columns in response to stimulation of layer 3 of either column. We examined whether GABAB receptor-mediated presynaptic inhibition affects the covariability of synaptic actions by intracortical axons between adjacent columns in slice preparations of the rat barrel cortex. Paired stimulations of superficial layer 3 evoked first and second excitatory postsynaptic currents (EPSCs) of varying amplitudes, yielding varying paired-pulse depression of EPSCs in layer 3 pyramidal cells that were located in the stimulated column, but not in its adjacent column. The amplitude of the second EPSC was inversely proportional to that of the first EPSC in layer 3 pyramidal cells in the stimulated column, yielding a negative correlation coefficient between the first and second EPSCs. Baclofen and CGP55845 attenuated paired-pulse depression and abolished the inverse relationship. Simultaneous recordings from two layer 3 pyramidal cells in the stimulated and adjacent columns revealed a positive correlation between the paired first EPSC amplitudes and a negative correlation between the paired second EPSC amplitudes, which, respectively, indicate the positive and negative covariability of synaptic actions by intracortical axons between the two adjacent columns. These results suggest that GABAB receptor-mediated presynaptic inhibition can reverse the positive covariability of inter-columnar synaptic actions, which may serve as a basis for inter-columnar desynchronisation.

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  • Tsukiboshi T, Sato H, Tanaka Y, Saito M, Toyoda H, Morimoto T, Turker KS, Maeda Y, Kang Y .  Illusion caused by vibration of muscle spindles reveals an involvement of muscle spindle inputs in regulating isometric contraction of masseter muscles .  Journal of Neurophysiology108 ( 9 ) 2524 - 2533   2012.11Reviewed

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    Spindle Ia afferents may be differentially involved in voluntary isometric contraction, depending on the pattern of synaptic connections in spindle reflex pathways. We investigated how isometric contraction of masseter muscles is regulated through the activity of their muscle spindles that contain the largest number of intrafusal fibers among skeletal muscle spindles by examining the effects of vibration of muscle spindles on the voluntary isometric contraction. Subjects were instructed to hold the jaw at resting position by counteracting ramp loads applied on lower molar teeth. In response to the increasing-ramp load, the root mean square (RMS) of masseter EMG activity almost linearly increased under no vibration, while displaying a steep linear increase followed by a slower increase under vibration. The regression line of the relationship between the load and RMS was significantly steeper under vibration than under no vibration, suggesting that the subjects overestimated the ramp load and excessively counteracted it as reflected in the emergence of bite pressure. In response to the decreasing-ramp load applied following the increasing one, the RMS hardly decreased under vibration unlike under no vibration, leading to a generation of bite pressure even after the offset of the negative-ramp load until the vibration was ceased. Thus the subjects overestimated the increasing rate of the load while underestimating the decreasing rate of the load, due to the vibration-induced illusion of jaw opening. These observations suggest that spindle Ia/II inputs play crucial roles both in estimating the load and in controlling the isometric contraction of masseter muscles in the jaw-closed position.

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  • Saito M, Toyoda H, Kawakami S, Sato H, Bae YC, Kang Y .  Capsaicin induces theta-band synchronization between gustatory and autonomic insular cortices .  The Journal of Neuroscience32 ( 39 ) 13470 - 13487   2012.9Reviewed

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    In the insular cortex, the primary gustatory area caudally adjoins the primary autonomic area that is involved in visceral sensory-motor integration. However, it has not been addressed whether neural activity in the gustatory insula (Gu-I) is coordinated with that in the autonomic insula (Au-I). We have demonstrated that TRPV1 activation in Gu-I induces theta-band synchronization between Gu-I and Au-I in rat slice preparations. Electron-microscopic immunohistochemistry revealed that TRPV1 immunoreactivity was much higher in Gu-I than in Au-I, and was mostly detected in dendritic spines receiving asymmetrical synapses. Whole-cell voltage-clamp recordings revealed that, in Gu-I, capsaicin-induced currents in layer 3 (L3) pyramidal cells (PCs) displayed no apparent desensitization, while those in layer 5 (L5) PCs displayed Ca2+-dependent desensitization, suggesting that L3 and L5 PCs respond differentially to TRPV1 activation. Voltage-sensitive dye imaging demonstrated that TRPV1 activation in Gu-I can alter an optical response with a monophasic and columnar temporospatial pattern evoked within Gu-I into an oscillatory one extending over Gu-I and Au-I. Power and cross-power spectral analyses of optical responses revealed theta-band synchronization between Gu-I and Au-I. Whole-cell current-clamp recordings demonstrated that such theta-band waves were mediated by sustained rhythmic firings at 4 and 8 Hz in L3 and L5 PCs, respectively. These results strongly suggested that theta-band oscillatory neural coordination between Gu-I and Au-I was induced by two distinct TRPV1-mediated theta-rhythm firings in L3 and L5 PCs in Gu-I. This network coordination induced by TRPV1 activation could be responsible for autonomic responses to tasting and ingesting spicy foods.

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  • Toyoda H, Saito M, Okazawa M, Hirao K, Sato H, Abe H, Takada K, Funabiki K, Takada M, Kaneko T, Kang Y .  Protein kinase G dynamically modulates TASK1-mediated leak K+ currents in cholinergic neurons of the basal forebrain .  The Journal of Neuroscience30 ( 16 ) 5677 - 5689   2010.4Reviewed

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    Leak K+ conductance generated by TASK1/3 channels is crucial for neuronal excitability. However, endogenous modulators activating TASK channels in neurons remained unknown. We previously reported that in the presumed cholinergic neurons of the basal forebrain (BF), activation of NO-cGMP-PKG (protein kinase G) pathway enhanced the TASK1-like leak K+ current (IK-leak). As 8-Br-cGMP enhanced the IK-leak mainly at pH 7.3 as if changing the IK-leak from TASK1-like to TASK3-like current, such an enhancement of the IK-leak would result either from an enhancement of hidden TASK3 component or from an acidic shift in the pH sensitivity profile of TASK1 component. In view of the report that protonation of TASK channel decreases its open probability, the present study was designed to examine whether the activation of PKG increases the conductance of TASK1 channels by reducing their binding affinity for H+, i.e., by increasing Kd for protonation, or not. We here demonstrate that PKG activation and inhibition respectively upregulate and downregulate TASK1 channels heterologously expressed in PKG-loaded HEK293 cells at physiological pH, by causing shifts in the Kd in the acidic and basic directions, respectively. Such PKG modulations of TASK1 channels were largely abolished by mutating pH sensor H98. In the BF neurons that were identified to express ChAT and TASK1 channels, similar dynamic modulations of TASK1-like pH sensitivity of IK-leak were caused by PKG. It is strongly suggested that PKG activation and inhibition dynamically modulate TASK1 currents at physiological pH by bidirectionally changing Kd values for protonation of the extracellular pH sensors of TASK1 channels in cholinergic BF neurons.

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  • Saito M, Toyoda H, Sato H, Ishii H, Kang Y .  Rapid use-dependent down-regulation of gamma-aminobutyric acid type A receptors in rat mesencephalic trigeminal neurons .  Journal of Neuroscience Research87 ( 14 ) 3120 - 3133   2009.11Reviewed

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    Rundown is ubiquitously seen in response to repetitive activation of receptor or ion channels as a use-dependent down-regulation through various mechanisms. In contrast to AMPA receptors, gamma-aminobutyric acid type A receptor (GABAAR) are believed to display no rapid use-dependent down-regulation. We report here a rapid use-dependent down-regulation of GABAAR in primary sensory neurons of rat mesencephalic trigeminal nucleus (MTN), which express synaptic GABAARs in addition to extrasynaptic ones, unlike other primary sensory neurons. When muscimol was repetitively puff-applied to an MTN neuron every 2 min before, during, and after the muscimol bath application for 5 min, both the GABAA responses obtained under both current- and voltage-clamp conditions were almost completely depressed during the bath application. However, the former and latter GABAA responses recovered to 26% +/- 7% and 36% +/- 7% of their control amplitudes, respectively, 15 min after washout of the bath-applied muscimol. By contrast, when examined in the presence of chelerythrine, a protein kinase C (PKC) inhibitor, together with a strin gent chelation of intracellular Ca2+, the puff responses were almost completely recovered, whereas those were recovered to 40-60% of the control by either chelerythrine or EGTA alone. A phosphatidylinositol 3-kinase inhibitor (PI3K), wortmannin, which blocks various signal transductions, including vesicular trafficking, significantly enhanced the rundown of the puff responses examined every 2 min. These findings indicate that the rundown of GABAA response in MTN neurons is mediated by the use-dependent down-regulation of GABAAR, which is reversed by PKC inhibition together with intracellular Ca2+ chelation, while being facilitated by PI3K inhibition.

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  • Toyoda H, Saito M, Sato H, Dempo Y, Ohashi A, Hirai T, Maeda Y, Kaneko T, Kang Y .  cGMP activates a pH-Sensitive leak K+ current in the presumed cholinergic neuron of basal forebrain .  Journal of Neurophysiology99 ( 5 ) 2126 - 2133   2008.5Reviewed

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    In an earlier study, we demonstrated that nitric oxide (NO) causes the long-lasting membrane hyperpolarization in the presumed basal forebrain cholinergic (BFC) neurons by cGMP-PKG-dependent activation of leak K+ currents in slice preparations. In the present study, we investigated the ionic mechanisms underlying the long-lasting membrane hyperpolarization with special interest in the pH sensitivity because 8-Br-cGMP-induced K+ current displayed Goldman-Hodgkin-Katz rectification characteristic of TWIK-related acid-sensitive K+ (TASK) channels. When examined with the ramp command pulse depolarizing from -130 to -40 mV, the presumed BFC neurons displayed a pH-sensitive leak K+ current that was larger in response to pH decrease from 8.3 to 7.3 than in response to pH decrease from 7.3 to 6.3. This K+ current was similar to TASK1 current in its pH sensitivity, whereas it was highly sensitive to Ba2+, unlike TASK1 current. The 8-Br-cGMP-induced K+ currents in the presumed BFC neurons were almost completely inhibited by lowering external pH to 6.3 as well as by bath application of 100 microM Ba2+ , consistent with the nature of the leak K+ current expressed in the presumed BFC neurons. After 8-Br-cGMP application, the K+ current obtained by pH decrease from 7.3 to 6.3 was larger than that obtained by pH decrease from pH 8.3 to 7.3, contrary to the case seen in the control condition. These observations strongly suggest that 8-Br-cGMP activates a pH- and Ba2+ -sensitive leak K+ current expressed in the presumed BFC neurons by modulating its pH sensitivity.

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  • Sato H, Shimanuki Y, Saito M, Toyoda H, Nokubi T, Maeda Y, Yamamoto T, Kang Y .  Differential columnar processing in local circuits of barrel and insular cortices .  The Journal of Neuroscience28 ( 12 ) 3076 - 3089   2008.3Reviewed

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    The columnar organization is most apparent in the whisker barrel cortex but seems less apparent in the gustatory insular cortex. We addressed here whether there are any differences between the two cortices in columnar information processing by comparing the spatiotemporal patterns of excitation spread in the two cortices using voltage-sensitive dye imaging. In contrast to the well known excitation spread in the horizontal direction in layer II/III induced in the barrel cortex by layer IV stimulation, the excitation caused in the insular cortex by stimulation of layer IV spread bidirectionally in the vertical direction into layers II/III and V/VI, displaying a columnar image pattern. Bicuculline or picrotoxin markedly extended the horizontal excitation spread in layer II/III in the barrel cortex, leading to a generation of excitation in the underlying layer V/VI, whereas those markedly increased the amplitude of optical responses throughout the whole column in the insular cortex, subsequently widening the columnar image pattern. Such synchronous activities as revealed by the horizontal and vertical excitation spreads were consistently induced in the barrel and insular cortices, respectively, even by stimulation of different layers with varying intensities. Thus, a unique functional column existed in the insular cortex, in which intracolumnar communication between the superficial and deep layers was prominent, and GABAA action is involved in the inhibition of the intracolumnar communication in contrast to its involvement in intercolumnar lateral inhibition in the barrel cortex. These results suggest that the columnar information processing may not be universal across the different cortical areas.

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  • Kang Y, Dempo Y, Ohashi A, Saito M, Toyoda H, Sato H, Koshino H, Maeda Y, Hirai T .  Nitric oxide activates leak K+ currents in the presumed cholinergic neuron of basal forebrain .  Journal of Neurophysiology98 ( 6 ) 3397 - 3410   2007.12Reviewed

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    Learning and memory are critically dependent on basal forebrain cholinergic (BFC) neuron excitability, which is modulated profoundly by leak K+ channels. Many neuro-modulators closing leak K+ channels have been reported, whereas their endogenous opener remained unknown. We here demonstrate that nitric oxide (NO) can be the endogenous opener of leak K+ channels in the presumed BFC neurons. Bath application of 1 mM S-nitroso-N-acetylpenicillamine (SNAP), an NO donor, induced a long-lasting hyperpolarization, which was often interrupted by a transient depolarization. Soluble guanylyl cyclase inhibitors prevented SNAP from inducing hyperpolarization but allowed SNAP to cause depolarization, whereas bath application of 0.2 mM 8-bromo-guanosine-3',5' -cyclomonophosphate (8-Br-cGMP) induced a similar long-lasting hyperpolarization alone. These observations indicate that the SNAP-induced hyperpolarization and depolarization are mediated by the cGMP-dependent and -independent processes, respectively. When examined with the ramp command pulse applied at -70 mV under the voltage-clamp condition, 8-Br-cGMP application induced the outward current that reversed at K+ equilibrium potential (E-K) and displayed Goldman-Hodgkin-Katz rectification, indicating the involvement of voltage-independent K+ current. By contrast, SNAP application in the presumed BFC neurons either dialyzed with the GTP-free internal solution or in the presence of 10 microM Rp-8-bromo-beta-phenyl-1, N-2-ethenoguanosine 3',5' -cyclic monophosphorothioate sodium salt, a protein kinase G (PKG) inhibitor, induced the inward current that reversed at potentials much more negative than E K and close to the reversal potential of Na+ -K+ pump current. These observations strongly suggest that NO activates leak K+ channels through cGMP-PKG-dependent pathway to markedly decrease the excitability in BFC neurons, while NO simultaneously causes depolarization by the inhibition of Na+ -K+ pump through ATP depletion.

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  • Kang Y, Saito M, Sato H, Toyoda H, Maeda Y, Hirai T, Bae YC .  Involvement of persistent Na+ current in spike initiation in primary sensory neurons of the rat mesencephalic trigeminal nucleus .  Journal of Neurophysiology97 ( 3 ) 2385 - 2393   2007.3Reviewed

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:American Physiological Society  

    It was recently shown that the persistent Na+ current (INaP) is generated in the proximal axon in response to somatic depolarization in neocortical pyramidal neurons, although the involvement of INaP in spike initiation is still unclear. Here we show a potential role of INaP in spike initiation of primary sensory neurons in the mesencephalic trigeminal nucleus (MTN) that display a back-propagation of the spike initiated in the stem axon toward the soma in response to soma depolarization. Riluzole (10 microM) and tetrodotoxin (TTX, 10 nM) caused an activation delay or a stepwise increase in the threshold for evoking soma spikes (S-spikes) without affecting the spike itself. Simultaneous patch-clamp recordings from the soma and axon hillock (AH) revealed that bath application of 50 nM TTX increased the delay in spike activation in response to soma depolarization, leaving the spike-backpropagation time from the AH to soma unchanged. This indicates that the increase in activation delay occurred in the stem axon. Furthermore, under a decreasing intracellular concentration gradient of QX-314 from the soma to AH created by QX-314-containing and QX-314-free patch pipettes, the amplitude and maximum rate of rise (MRR) of AH-spikes decreased with an increase in the activation delay following repetition of current-pulse injections, whereas S-spikes displayed decreases of considerably lesser degree in amplitude and MRR. This suggests that compared to S-spikes, AH-spikes more accurately reflect the attenuation of axonal spike by QX-314, consistent with the nature of spike backpropagation. These observations strongly suggest that low-voltage -activated INaP is involved in spike initiation in the stem axon of MTN neurons.

    DOI: 10.1152/jn.01191.2006

    Web of Science

    PubMed

  • Saito M, Murai Y, Sato H, Bae YC, Akaike T, Takada M, Kang Y .  Two opposing roles of 4-AP-sensitive K+ current in initiation and invasion of spikes in rat mesencephalic trigeminal neurons .  Journal of Neurophysiology96 ( 4 ) 1887 - 1901   2007.3Reviewed

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    Language:English   Publishing type:Doctoral thesis  

    The axon initial segment plays important roles in spike initiation and invasion of axonal spikes into the soma. Among primary sensory neurons, those in the mesencephalic trigeminal nucleus (MTN) are exceptional in their ability to initiate soma spikes (S-spikes) in response to synaptic inputs, consequently displaying two kinds of S-spikes, one caused by invasion of an axonal spike arising from the sensory receptor and the other initiated by somatic inputs. We investigated where spikes are initiated in such MTN neurons and whether there are any differences between the two kinds of S-spikes. Simultaneous patch-clamp recordings from the soma and axon hillock revealed a spike-backpropagation from the spike-initiation site in the stem axon to the soma in response to 1-ms somatic current pulse, which disclosed the delayed emergence of S-spikes after the current-pulse offset. These initiated S-spikes were smaller in amplitude than S-spikes generated by stimulation of the stem axon; however, 4-AP (<= 0.5 mM) eliminated the amplitude difference. Furthermore, 4-AP dramatically shortened the delay in spike initiation without affecting the spike-backpropagation time in the stem axon, whereas it substantially prolonged the refractory period of S-spikes arising from axonal-spike invasion without significantly affecting that of presumed axonal spikes. These observations suggest that 4-AP sensitive K+ currents exert two opposing effects on S-spikes depending on their origins: suppression of spike initiation and facilitation of axonal-spike invasion at higher frequencies. Consistent with these findings, strong immunoreactivities for Kv1.1 and Kv1.6, among 4-AP-sensitive and low-voltage-activated Kv1 family examined, were detected in the soma but not in the stem axon of MTN neurons.

    DOI: 10.1152/jn.00176.2006

    PubMed

    Other Link: http://jn.physiology.org/content/96/4/1887.long

  • Saito M, Murai Y, Sato H, Bae YC, Akaike T, Takada M, Kang Y .  Two opposing roles of 4-AP-sensitive K+ current in initiation and invasion of spikes in rat mesencephalic trigeminal neurons .  Journal of Neurophysiology96 ( 4 ) 1887 - 1901   2006.10Reviewed

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    Authorship:Lead author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:American Physiological Society  

    The axon initial segment plays important roles in spike initiation and invasion of axonal spikes into the soma. Among primary sensory neurons, those in the mesencephalic trigeminal nucleus (MTN) are exceptional in their ability to initiate soma spikes (S-spikes) in response to synaptic inputs, consequently displaying two kinds of S-spikes, one caused by invasion of an axonal spike arising from the sensory receptor and the other initiated by somatic inputs. We investigated where spikes are initiated in such MTN neurons and whether there are any differences between the two kinds of S-spikes. Simultaneous patch-clamp recordings from the soma and axon hillock revealed a spike-backpropagation from the spike-initiation site in the stem axon to the soma in response to 1-ms somatic current pulse, which disclosed the delayed emergence of S-spikes after the current-pulse offset. These initiated S-spikes were smaller in amplitude than S-spikes generated by stimulation of the stem axon; however, 4-AP (<= 0.5 mM) eliminated the amplitude difference. Furthermore, 4-AP dramatically shortened the delay in spike initiation without affecting the spike-backpropagation time in the stem axon, whereas it substantially prolonged the refractory period of S-spikes arising from axonal-spike invasion without significantly affecting that of presumed axonal spikes. These observations suggest that 4-AP sensitive K+ currents exert two opposing effects on S-spikes depending on their origins: suppression of spike initiation and facilitation of axonal-spike invasion at higher frequencies. Consistent with these findings, strong immunoreactivities for Kv1.1 and Kv1.6, among 4-AP-sensitive and low-voltage-activated Kv1 family examined, were detected in the soma but not in the stem axon of MTN neurons.

    DOI: 10.1152/jn.00176.2006

    Web of Science

    PubMed

  • Fukushi E, Saito M, Sato H, Endo T, Hamaue N, Hirafuji M, Minami M, Kang Y .  Functional roles of 5-hydroxytryptamine 3/4 receptors in neurons of rat dorsal motor nucleus of the vagus .  Neuroscience141 ( 2 ) 675 - 685   2006.8Reviewed

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:International Brain Research Organization  

    In neurons of dorsal motor nucleus of the vagus that is involved in the gastric motility and possibly emesis, application of 5-hydroxytryptamine produces membrane depolarization, and suppresses spike-repolarization and spikeafterhyperpolarization, suggesting divergent effects of 5-hydroxytryptamine through activating multiple subtypes of 5-hydroxytryptamine receptors. However, only the role of 5-hydroxytryptamine 2A receptors has been established to be responsible for the depolarization, and the mechanisms underlying the modulation of spikes remain unknown although a role of 5-hydroxytryptamine 4 receptors was implicated in modulations of spikes. There is now increasing evidence for the role of 5-hydroxytryptamine receptors in neurons involved in generating emesis following administration of anticancer drug. Since antagonists of 5-hydroxytryptamine 3/4 receptors are widely used as anti-emetic drugs, we have reevaluated the functional roles of 5-hydroxytryptamine 3/4 receptors of dorsal motor nucleus of the vagus neurons, especially in modulating transient outward currents that are presumed to be involved in spike-repolarization and spikeafterhyperpolarization. Whole-cell patch-clamp recordings were made from the dorsal motor nucleus of the vagus neurons, which were identified by a retrograde tracing method with dextran-tetramethyrhodamine-lysine injected into a bundle of abdominal vagus nerves. Under a voltage-clamp condition, dorsal motor nucleus of the vagus neurons expressed a prominent A-like current. The activation of 5-hydroxytryptamine 3 receptors reversibly increased the resting membrane conductance while the activation of 5-hydroxytryptamine 4 receptors led to an almost irreversible decrease in the A-like current. A long-lasting suppression of A-like current by transient activation of 5-hydroxytryptamine 4 receptors would result in a long-lasting increase in the excitability of dorsal motor nucleus of the vagus neurons, which might be involved in generation of the long-lasting facilitation of gastric motility or in generation of the long-lasting gastric relaxation through the activation of enteric non-adrenergic non-cholinergic neurons as implicated in the delayed emesis induced by anticancer drugs.

    DOI: 10.1016/j.neuroscience.2006.04.025

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    PubMed

  • Kang Y, Notomi T, Saito M, Zhang W, Shigemoto R .  Bidirectional interactions between H-channels and Na+-K+ pumps in mesencephalic trigeminal neurons .  The Journal of Neuroscience24 ( 14 ) 3694 - 3702   2004.4Reviewed

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Society for Neuroscience  

    The Na+ -K+ pump current (Ip) and the h-current (Ih) flowing through hyperpolarization-activated channels (h-channels) participate in generating the resting potential. These two currents are thought to be produced independently. We show here bidirectional interactions between Na+-K+ pumps and h-channels in mesencephalic trigeminal neurons. Activation of Ih leads to the generation of two types of ouabain-sensitive Ip with temporal profiles similar to those of instantaneous and slow components of Ih, presumably reflecting Na+ transients in a restricted cellular space. Moreover, the Ip activated by instantaneous Ih can facilitate the subsequent activation of slow Ih. Such counteractive and cooperative interactions were also disclosed by replacing extracellular Na+ with Li+, which is permeant through h-channels but does not stimulate the Na+ -K+ pump as strongly as Na+ ions. These observations indicate that the interactions are bidirectional and mediated by Na+ ions. Also after substitution of extracellular Na+ with Li+, the tail Ih was reduced markedly despite an enhancement of Ih itself, attributable to a negative shift of the reversal potential for Ih presumably caused by intracellular accumulation of Li+ ions. This suggests the presence of a microdomain where the interactions can take place. Thus, the bidirectional interactions between Na+ -K+ pumps and h-channels are likely to be mediated by Na+ microdomain. Consistent with these findings, hyperpolarization-activated and cyclic nucleotide-modulated subunits (HCN1/2) and the Na+ -K+ pump alpha3 isoform were colocalized in plasma membrane of mesencephalic trigeminal neurons having numerous spines.

    DOI: 10.1523/JNEUROSCI.5641-03.2004

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    PubMed

  • Inoue T, Itoh S, Wakisaka S, Ogawa S, Saito M, Morimoto T .  Involvement of 5-HT7 receptors in serotonergic effects on spike afterpotentials in presumed jaw-closing motoneurons of rats .  Brain Research954 ( 2 ) 202 - 211   2002.11Reviewed

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:International Brain Research Organization  

    Intracellular recordings were obtained from rat presumed jaw-closing motoneurons in slice preparations to investigate the involvement of the serotonin, (5-HT7) receptors in serotonergic inhibition of the postspike medium-duration afterhyperpolarization (mAHP) and enhancement of the afterdepolarization (ADP). 5-HT-induced suppression of the mAHP and enhancement of the ADP were mimicked by application of the 5-HT1A/7 receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) and antagonized by the 5-HT2/6/7 receptor antagonist clozapine, whereas the 5-HT2 receptor agonist alpha-methyl-5-hydroxytryptamine (alpha-methyl-5-HT) did not affect the mAHP and ADP 8-OH-DPAT-induced attenuation of the mAHP and enhancement of the ADP were also antagonized by clozapine and another 5-HT2/6/7 receptor antagonist ritanserin, whereas the 5-HT1A receptor antagonist pindolol failed to block the 8-OH-DPAT-induced effects on the mAHP and ADP 8-OH-DPAT-induced suppression of the mAHP and enhancement of the ADP were also antagonized by a protein kinase A (PKA) inhibitor H89, whereas 8-OH-DPAT could inhibit the mAHP and enhance the ADP in the presence of a protein kinase C (PKC) inhibitor chelerythrine. The 8-OH-DPAT-induced suppression of the mAHP was enhanced under raised [Ca2+]o and this enhancement was reduced by chelerythrine. It is suggested that the 5-HT7 receptors are involved in 5-HT-induced attenuation of the mAHP and enhancement of the ADP through activation of PKA, and the attenuation of mAHP through the 5-HT7 receptors is enhanced under raised [Ca2+]o by PKC activation.

    DOI: 10.1016/S0006-8993(02)03286-9

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    PubMed

  • Hidaka O, Iwasaki M, Saito M, Morimoto T .  Influence of clenching intensity on bite force balance, occlusal contact area, and average bite pressure .  Journal of Dental Research78 ( 7 ) 1336 - 1344   1999.7Reviewed

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:American Dental Association, International Association for Dental Research, American Association for Dental Research  

    It has been difficult for investigators to simultaneously and reliably evaluate bite force in the intercuspal position with the area and location of occlusal contacts. This study was designed to investigate the variations in these parameters with respect to two factors: three levels of clenching and the preferred chewing side. Human subjects with normal occlusion were examined with a recently developed system (Dental Prescale Occluzer, Fuji Film,Tokyo, Japan). The three levels of clenching intensity were assessed by masseteric EMG activity and included the maximum voluntary contraction, and 30% and 60% of the maximum. The results indicated that the bite force and occlusal contact area on the whole dental arch increased with clenching intensity. In contrast, the average bite pressure, obtained by dividing the bite force by the contact area, remained unchanged regardless of the clenching intensity. As the clenching intensity increased, the medio-lateral position of the bite force balancing point shifted significantly(P < 0.01) from the preferred chewing side toward the midline. The antero-posterior position remained stable in a range between the distal third of the first molar and the mesial third of the second molar. The bite force and occlusal contact area, which were mainly on the molars, increased with the clenching intensity, whereas the proportions of these two variables on each upper tooth usually did not change significantly. The exception was the second molar on the non-preferred chewing side. When comparisons were made between pairs of specific upper teeth of same name, usually no significant difference was found in bite force or occlusal contact area, regardless of the clenching level. Again, the exception to this observation was the second molar on the preferred chewing side, which had a larger area at the 30% clenching level. The results in normal subjects suggest that as the clenching intensity increases in the intercuspal position, the bite force adjusts to a position where it is well-balanced. This adjustment may prevent damage and overload to the teeth and temporomandibular joints.

    DOI: 10.1177/00220345990780070801

    Web of Science

    PubMed

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Books

  • 歯科生理学実習 第2版(岩田 幸一, 井上 富雄, 舩橋 誠, 加藤 隆史, 重村 憲徳, 篠田 雅路, 小野 堅太郎 編)

    岩田 幸一, 井上 富雄, 舩橋 誠, 加藤 隆史, 重村 憲徳, 篠田 雅路, 小野 堅太郎, 上阪 直史, 奥村 敏, 澁川 義幸, 北川 純一, 石井 久淑, 吉垣 純子, 合田 征司, 増田 裕次, 村本 和世, 佐藤 義英, 山村 健介, 齋藤 充( Role: Contributor ,  19.発声と構音(本文及び補足資料))

    医歯薬出版  2022.3  ( ISBN:978-4-263-45869-3 )

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    Total pages:140   Responsible for pages:107-109   Language:Japanese Book type:Textbook, survey, introduction

  • Basic Physiology for Dental Students, 7th Edition

    Saito M( Role: Contributor ,  Chapter 10: Sensory functions: Vision, Audition, and Equilibrioception)

    Ishiyaku Publishers  2020.3 

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    Total pages:476   Responsible for pages:192-206   Language:Japanese Book type:Textbook, survey, introduction

  • Basic Physiology for Dental Students, 5th Edition

    ( Role: Contributor)

    Ishiyaku Publishers  2008.2 

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    Total pages:466   Responsible for pages:242-249   Language:Japanese Book type:Textbook, survey, introduction

  • Basic Physiology for Dental Students, 4th Edition

    ( Role: Contributor)

    Ishiyaku Publishers  2003.3 

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    Total pages:431   Responsible for pages:233-249   Language:Japanese Book type:Textbook, survey, introduction

MISC

  • 脳の健康は歯の健康から? -歯の喪失と認知症の関係-

    齋藤 充

    鹿児島県歯科医師会会報   2019.7

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  • 閉口筋感覚-運動制御機構の特異性

    齋藤 充

    鹿児島大学歯学部紀要   36   11 - 18   2016.3

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    Language:Japanese   Publishing type:Article, review, commentary, editorial, etc. (bulletin of university, research institution)   Publisher:鹿児島大学歯学部  

    Institutional Repository URL

  • 総説特集II 香辛料の味修飾作用及び消化管を介した代謝調節作用-4 カプサイシンの島皮質での受容による内臓-内臓間自律神経反射の修飾の可能性

    齋藤 充

    日本味と匂学会誌   21 ( 1 )   55 - 60   2014.4

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    Language:Japanese   Publishing type:Article, review, commentary, editorial, etc. (scientific journal)   Publisher:日本味と匂学会  

    トウガラシを含む食品を摂取すると、「熱さを伴う辛さ」を覚え、それに続き顔面からの発汗や血液循環の亢進などの様々な身体反応が生じる。これらは、トウガラシの辛味の主成分であるカプサイシンが末梢のTRPV1を活性化することによって生じる内臓-内臓反射であると考えられてきたが、その詳細は未だ明らかではない。近年、ヒトがカプサイシンを摂取すると島皮質味覚野に神経活動が生じることが、fMRIを用いた研究によって明らかとなった。そこで、トウガラシ摂取時にみられる身体反応における島皮質味覚野の関与について検討した。

    CiNii Research

  • 「熱くて辛い」味の認知が内臓機能を賦活化するメカニズム

    齋藤 充

    大阪大学歯学雑誌   58 ( 1 )   17 - 20   2013.10

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    Language:Japanese   Publishing type:Article, review, commentary, editorial, etc. (bulletin of university, research institution)   Publisher:大阪大学歯学会  

  • 【口腔領域をめぐる神経基盤】 噛みしめ運動における咬筋運動ニューロン序列動員の階層性制御機構

    姜 英男,豊田 博紀,齋藤 充,佐藤 元

    脳21   14 ( 4 )   385 - 391   2011.10

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    Language:Japanese   Publishing type:Article, review, commentary, editorial, etc. (scientific journal)   Publisher:金芳堂  

    咀嚼サイクルの遅い閉口相は、食物の咀嚼において主要な役割を果たしている。しかしながら、遅い閉口相の神経機構は未だ明らかではない。主要な閉口筋である咬筋は、全身の骨格筋中で最大数の錘内筋を含む筋紡錘をもつため、それを支配するγ運動ニューロンは閉口運動において特別な役割を担う。遅い閉口相における閉口筋の等尺性収縮は、閉口筋運動単位の序列動員によって実現されている。運動単位は、運動ニューロンの軸索径の小さいもの、つまり、伝導速度の遅いものから順に動員されることが知られており、これを「サイズの原理」という。近年、2ポアドメイン酸感受性カリウムチャネルの一種であるTASKチャネルがニューロンの入力抵抗を支配的に決定し、咬筋運動ニューロンにも豊富に発現していることが明らかになった。運動ニューロンの軸索径は細胞径と比例し、入力抵抗とは反比例する。運動ニューロンの入力抵抗は、さまざまな神経伝達物質により修飾されるため、序列動員も修飾を受けることが想定される。本稿では、回路レベルの制御機構として、咬筋運動ニューロンの序列動員における筋紡錘Ia感覚信号の役割と、分子レベルでの制御機構として、序列動員におけるTASKチャネルの関与について概説する。

    Other Link: https://mol.medicalonline.jp/archive/search?jo=ac5nonid&ye=2011&vo=14&issue=4

  • Recruitment of masseter motoneurons by spindle Ia inputs and its modulation by leak K+ channels Reviewed

    Kang Y, Toyoda H, Saito M, Sato H

    Interface Oral Health Science 2009 (Sasano T and Suzuki O Eds.)   60 - 65   2010.5

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    Language:English   Publishing type:Article, review, commentary, editorial, etc. (international conference proceedings)   Publisher:Springer Japan  

    The slow-closing phase of the mastication cycle plays a major role in the mastication of foods. However, the neuronal mechanism underlying the slow-closing phase remains unknown. During the slow-closing phase, isometric contraction of jaw-closing muscles is developed through the recruitment of jaw-closing motoneurons (MNs). It is well established that motor units are recruited depending on the order of sizes or input resistances (IRs) of MNs, which is known as the size principle. TASK 1/3 channels are recently found to be the molecular correlates of the IR, and also found to be expressed in the masseter MNs. The orderly recruitment of masseter MNs may be modified by the activity of TASK1/3 channels. In this chapter, we discuss the synaptic mechanisms underlying the orderly recruitment of masseter MNs that occurs during the slow-closing phase, together with the mechanism for the modulation of the orderly recruitment of motor units.

    DOI: 10.1007/978-4-431-99644-6_9

  • Chapter 11. Recruitment of masseter motoneurons by the presumed spindle Ia inputs Reviewed

    Kang Y, Saito M, Toyoda H, Sato H

    Progress in Brain Research   187 (Breath, Walk and Chew: The Neural Challenge: Part I)   163 - 171   2010

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    Language:English   Publishing type:Article, review, commentary, editorial, etc. (scientific journal)   Publisher:Elsevier  

    The slow-closing phase of the mastication cycle plays a major role in the mastication of foods. However, the neuronal mechanism underlying the slow-closing phase remains unknown. The isometric contraction of jaw-closing muscles is developed through the recruitment of jaw-closing motoneurons during the slow-closing phase. It is well established that motor units are recruited depending on the order of sizes or input resistances (IRs) of motoneurons, which is known as the size principle. Two-pore-domain acid-sensitive K+ (TASK1/3) channels are recently found to be the molecular correlates of the IR, and also found to be expressed in the masseter motoneurons. Here, we addressed the question whether spindle Ia inputs onto masseter motoneurons can induce the orderly recruitment of motoneurons in slice preparations of the rat brain using voltage-sensitive dye imaging and whole-cell patch-clamp methods. Voltage-sensitive dye imaging revealed the recruitment of many motoneurons in the whole nucleus of masseter in response to repetitive stimulation of the presumed spindle Ia inputs. Dual whole-cell recordings obtained from two adjacent motoneurons revealed the IR-ordered recruitment of motoneurons in response to repetitive stimulation of the presumed spindle Ia inputs. Thus, Ia inputs are likely to play a crucial role in the orderly recruitment of motoneurons of the trigeminal motor nucleus, which would be progressed during the slow-closing phase of the mastication cycle. Possible involvements of TASK channels in the orderly recruitment are discussed.

    DOI: 10.1016/B978-0-444-53613-6.00011-3

    PubMed

  • Rank-ordered recruitment of masseter motoneurons by the activity of mesencephalic trigeminal neurons during slow closing phase of mastication cycle Reviewed

    Kang Y, Saito M, Toyoda H, Sato H

    Journal of Oral Biosciences   52 ( 4 )   330 - 335   2010

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    Language:English   Publishing type:Article, review, commentary, editorial, etc. (scientific journal)   Publisher:Japanese Association for Oral Biology  

    DOI: 10.1016/S1349-0079(10)80013-1

  • Occlusal-masticatory function and learning and memory: Immunohistochemical, biochemical, behavioral and electrophysiological studies in rats Reviewed

    Hirai T, Kang Y, Koshino H, Kawanishi K, Toyoshita Y, Ikeda Y, Saito M

    Japan Dental Science Review   46 ( 2 )   143 - 149   2010

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    Language:English   Publishing type:Article, review, commentary, editorial, etc. (scientific journal)   Publisher:Japanese Association for Dental Science  

    DOI: 10.1016/j.jdsr.2009.12.002

  • 三叉神経中脳路核ニューロンにおけるインパルストラフィッキング

    姜 英男,豊田 博紀,齋藤 充,佐藤 元

    先端歯科医学のカッティング・エッジ (米田 俊之 編)   157 - 166   2008.3

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    Language:Japanese   Publishing type:Article, review, commentary, editorial, etc. (other)   Publisher:大阪大学出版会  

    Other Link: http://www.osaka-up.or.jp/books/ISBN978-4-87259-233-7.html

  • Impulse trafficking in neurons of the mesencephalic trigeminal nucleus Reviewed

    Kang Y, Saito M

    International Journal of Oral Biology   31 ( 4 )   113 - 118   2006.12

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    Language:English   Publishing type:Article, review, commentary, editorial, etc. (scientific journal)   Publisher:The Korean Academy of Oral Biology  

    In the primary sensory neuron of the mesencephalic trigeminal nucleus (MTN), the peripheral axon supplies a large number of annulospiral endings surrounding intrafusal fibers encapsulated in single muscle spindles while the central axon sends only a few number of synapses onto single alpha-motoneuron.(alpha-MN). Therefore, the alpha-gamma linkage is thought to be very crucial in the jaw-closing movement. Spike activity in a gamma-motoneuron (gamma-MN) would induce a large number of impulses in single peripheral axons by activating many intrafusal fibers simultaneously, subsequently causing an activation of alpha-MN in spite of the small number of synapses. Thus, the activity of gamma-MN may be vital for modulation of jaw-closing movements. Independently of such a spindle activity modulated by gamma-MN, somatic depolarization in MTN neurons is known to trigger the oscillatory spike activity. Nevertheless, the trafficking of these spikes arising from the two distinct sources of MTN neurons is not well understood. In this short review, switching among multiple functional modes of MTN neurons is discussed. Subsequently, it will be discussed which mode can support the alpha-gamma linkage. In our most recent study, simultaneous patch-clamp recordings from the soma and axon hillock revealed a spike-back-propagation from the spike-initiation site in the stem axon to the soma in response to a somatic current pulse. The persistent Na+ current was found to be responsible for the spike-initiation in the stem axon, the activation threshold of which was lower than those of soma spikes. Somatic inputs or impulses arising from the sensory ending, whichever trigger spikes in the stem axon first, would be forwarded through the central axon to the target synapse. We also demonstrated that at hyperpolarized membrane potentials, 4-AP-sensitive K+ current (IK4AP) exerts two opposing effects on spikes depending on their origins; the suppression of spike initiation by increasing the apparent electrotonic distance between the soma and the spike-initiation site, and the facilitation of axonal spike invasion at higher frequencies by decreasing the spike duration and the refractory period. Through this mechanism, the spindle activity caused by gamma-MN would be safely forwarded to alpha-MN. Thus, soma spikes shaped differentially by this IK4AP depending on their origins would reflect which one of the two inputs was forwarded to the target synapses.

    Other Link: http://www.kijob.or.kr/journal/article.php?code=1069

  • 顎口腔機能の解明に向けた戦略的アプローチ

    姜 英男,小林 真之,戸田 孝史,齋藤 充

    先端歯科医学の創生 - フロンティアバイオデンティストリー (浜田 茂幸,米田 俊之 編)   231 - 242   2005.2

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    Language:Japanese   Publishing type:Article, review, commentary, editorial, etc. (other)   Publisher:大阪大学出版会  

    Other Link: http://www.osaka-up.or.jp/books/ISBN978-4-87259-185-9.html

  • 咀嚼運動と脳機能

    姜 英男,齋藤 充,平井 敏博

    歯界展望   102 ( 2 )   405 - 416   2003.8

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    Language:Japanese   Publishing type:Article, review, commentary, editorial, etc. (trade magazine, newspaper, online media)   Publisher:医歯薬出版  

    Other Link: https://www.ishiyaku.co.jp/search/details.aspx?bookcode=021022

  • Excitatory effects of noradrenaline on trigeminal motoneurons in rats Reviewed

    Inoue T, Saito M, Kobayashi M

    Dentistry in Japan (継続後誌:The Japan Dental Science Review,2008年~)   38   33 - 35   2002

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    Language:English   Publishing type:Article, review, commentary, editorial, etc. (scientific journal)   Publisher:Japanese Association for Dental Science  

  • 咀嚼筋活動の調節機構

    井上 富雄,鶴岡 正吉,佐野 正和,山上 芳雄,臼井 美恵子,齋藤 充,松谷 貴代

    昭和歯学会雑誌   21 ( 1 )   58 - 63   2001.3

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    Language:Japanese   Publishing type:Article, review, commentary, editorial, etc. (bulletin of university, research institution)   Publisher:昭和歯学会  

    咀嚼する食品の物理的性状にしたがって咀嚼筋活動は適切に調節されるが、この調節には歯根膜感覚受容器と閉口筋筋紡錘からの感覚情報が重要な役割を果たしている。三叉神経運動核周囲の網様体には、口腔領域からの感覚情報が入力し、出力を三叉神経運動核に送るニューロンが存在する。このようなニューロンは咀嚼筋活動の調節に関与している可能性がある。閉口筋運動ニューロンに口腔領域からの感覚によって修飾を受けた咀嚼の運動指令が入力するが、同時にセロトニン入力によって興奮性が増大する等の変調を受ける。以上のようなメカニズムは、咀嚼する食物の性状に見合った適切な咀嚼力の発現に役立っていると考えられる。

    CiNii Research

    Other Link: https://www.jstage.jst.go.jp/article/dentalmedres1981/21/1/21_58/_article/-char/ja/

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Presentations

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Works

  • Neuroscience in Oral Function 研究会 第2回

    佐原 資謹,姜 英男,吉村 弘,原田 英光,井上 富雄,若森 実,澁川 義幸,小林 真之,深見 秀之,吉田 卓史,齋藤 充

    2014.12

  • Neuroscience in Oral Function 研究会 第1回

    姜 英男,佐原 資謹,吉村 弘,井上 富雄,若森 実,兼松 隆,小林 真之,豊田 博紀,齋藤 充,佐藤 元

    2014.9

Awards

  • 平成24年度 弓倉学術奨励賞

    2013.1   大阪大学大学院歯学研究科   カプサイシンによって惹起される島皮質味覚野-自律機能関連領野間のθリズム同期化現象

    齋藤 充

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    Country:Japan

Research Projects

  • Development of quantitative evaluation method of masticatory function based on facial expression analysis during mastication movements of children with developmental disabilities

    Grant number:22K11388  2022.4 - 2025.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (C)

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    Grant amount:\3380000 ( Direct Cost: \2600000 、 Indirect Cost:\780000 )

  • The role of mesencephalic trigeminal neurons that release NT-3 as paracrine signals in the maintenance/viability of LC neurons.

    Grant number:21K06441  2021.4 - 2024.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (C)

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    Grant amount:\4160000 ( Direct Cost: \3200000 、 Indirect Cost:\960000 )

  • Effects of brain-gut peptides on the amelioration of stress-induced abnormalities of maxillofacial function.

    Grant number:18K09838  2018.4 - 2022.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (C)

    Yagi Takakazu

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    Grant amount:\4420000 ( Direct Cost: \3400000 、 Indirect Cost:\1020000 )

    The purpose of this study was to elucidate some of the mechanisms of the development of bruxism-like movements induced by intracerebroventricular administration of corticosteroid releasing factor (CRF), a stressor, or by physical restraints, focusing on the relationship between stress and the trigeminal nervous system. The parabrachial nucleus of the connecting arm and the locus coeruleus in the region of the trigeminal mesencephalic tract nucleus were positive for anti-c-Fos antibodies. In restraint stress, immunopositive cells were observed around the trigeminal motor nucleus and in the lateral nucleus of the hypothalamus, and double-labeled cells of c-Fos and orexin were observed. These results suggest that the connecting arm antinuclear nucleus, locus coeruleus, and orexin cells may be potentially contributing to bruxism-like behavior.

  • The mechanism for the generation of theta-rhythm synchronization between the gastatory and gastrointestinal insular corticies

    Grant number:17K07055  2017.4 - 2022.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (C)

    Kang Youngnam

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    Grant amount:\4940000 ( Direct Cost: \3800000 、 Indirect Cost:\1140000 )

    It was found that various functions occur as a result of the oscillatory synchronization between the two neuronal populations in the gustatory and its caudal gastrointestinal insular cortices and between those in the gustatory and its rostral pain insular cortices. CB1 receptor activation in the gustatory insular cortex causes oscillatory synchronization at theta rhythm between the two neuronal populations in the gustatory and gastrointestinal insular cortices, which would lead to overeating sweet and umami taste foods. Delta rhythm oscillatory synchronization would occur during taste aversion learning, resulting in unbalanced diet. In addition, it was clarified that activity of GABAergic neurons may be involved in delta rhythm generation while theta rhythm was not affected by the blockade of GABA receptors. Furthermore, it was revealed that a 24-hour fasting suppressed the second phase of the formalin-induced pain response through the activation of CB1 receptors.

  • 運動野からのトップダウン痛覚抑制機序の解明: 三叉神経痛の治療法開発へ向けて

    2016.4 - 2020.3

    科学研究費補助金  基盤研究(C)

    倉本 恵梨子、桑木 共之,齋藤 充,柏谷 英樹,大野 幸,後藤 哲哉,岩井 治樹

  • 咬合不全が高次脳機能低下を招く神経機構の解明:三叉神経中脳路核周囲の回路網の解析

    2016.4 - 2019.9

    科学研究費補助金  基盤研究(C)

    齋藤 充、倉本 恵梨子,姜 英男

  • 光遺伝学的手法を用いた咬筋運動ニューロン興奮性制御におけるTASKの役割の解析

    2012.4 - 2016.3

    科学研究費補助金  基盤研究(C)

  • 光刺激を用いた入力線維の選択的活性化による運動ニューロン序列動員神経機構の解明

    2012.4 - 2014.3

    科学研究費補助金  挑戦的萌芽研究

    姜 英男、齋藤 充,佐藤 元

  • Modulation of rank-ordered recruitment of motor units in the jaw-closing movement by leak K+ channels

    2010.4 - 2014.3

    Grant-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research(B)

  • 培養細胞発現系も用いたTASK電流の解析

    2010.4 - 2012.3

    地方自治体  国内共同研究 

    姜 英男、岡澤 慎,豊田 博紀,齋藤 充

  • Synaptic Inputs Switching Functional Modes in Primary Sensory Neurons of Rat Trigeminal Mesencephalic Nucleus

    2009.4 - 2012.3

    Grant-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research(C)

  • バレル野と味覚野における領野特異的機能発現に関与する局所回路

    2008.4 - 2010.3

    科学研究費補助金  特定領域研究

    姜 英男、齋藤 充

  • 噛みしめ運動による脳機能低下抑制の神経メカニズム

    2008.4 - 2009.3

    民間企業  国内共同研究 

    姜 英男、川上 晋平,豊田 博紀,齋藤 充,佐藤 元

  • Neural mechanisms of gamma-motor system underlying modulation of bite force

    2007.4 - 2009.3

    Grant-in-Aid for Scientific Research  Grant-in-Aid for Young Scientists(B)

  • 噛みしめ運動学習におけるチューインガムの役割

    2007.4 - 2009.3

    民間企業  一般受託研究 

    姜 英男、豊田 博紀,齋藤 充,佐藤 元

  • Modulation of excetability in primary sensory neurons

    2006.4 - 2008.3

    Grant-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research(C)

  • GABA(A)受容体過剰発現マウスにおける大脳皮質側方抑制及びカラム間同期機構

    2006.4 - 2008.3

    科学研究費補助金  特定領域研究

    姜 英男、齋藤 充

  • 大脳皮質興奮性入力の機能単位間での脱同期化に関与するGABA(B)シナプス前抑制

    2005.4 - 2006.3

    科学研究費補助金  特定領域研究

    姜 英男、小林 真之,齋藤 充

  • 大脳皮質機能円柱内及び機能円柱間局所回路の動作機構

    2003.4 - 2005.3

    科学研究費補助金  特定領域研究

    姜 英男、小林 真之,齋藤 充

  • Regulatory Mechanisms of Excitability in the Mesencephalic Trigeminal Neurons

    2002.4 - 2005.3

    Grant-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research(B)

  • 大脳皮質バレル領野における抑制性局所回路によるニューロン活動の同期化・脱同期化制御機構

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    Grant type:Competitive

  • 三叉神経運動ニューロンの電気生理学的特性

    その他の研究制度 

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    Grant type:Competitive

  • 三叉神経中脳路核ニューロンの電気生理学的特性

    その他の研究制度 

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    Grant type:Competitive

  • Electrophysiological properties of trigeminal moroneurons

    The Other Research Programs 

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    Grant type:Competitive

  • Electrophysiological properties of mesencephalic trigeminal neurons

    The Other Research Programs 

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    Grant type:Competitive

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