2003 Fiscal Year Final Research Report Summary
Defference in physiological and mophological properties between jaw-closing and opening motoneurons
| Project/Area Number |
14571777
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Functional basic dentistry
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| Research Institution | Showa University |
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Principal Investigator |
INOUE Tomio Showa University, School of Dentistry, Professor, 歯学部, 教授 (70184760)
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| Co-Investigator(Kenkyū-buntansha) |
OHATA Hisayuki Showa University, School of Pharmaceutical Sciences, Associate Professor, 薬学部, 助教授 (00119166)
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| Project Period (FY) |
2002 – 2003
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| Keywords | trigeminal / motoneuron / afterhyperpolarization / patch clamp / slice preparation / jaw-closing muscle / jaw-opening muscle |
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| Research Abstract |
Whole cell patch clamp recordings were made from masseter motoneurons (MaMNs) and digastric motoneurons (DiMNs) in neonatal rat brainstem slice preparations to study firing properties of jaw-closing and opening motoneurons. Input resistance and membrane time constant of MaMNs were smaller than those of DiMNs. Amplitude of the post-spike medium-duration afterhyperpolarization (mAHP) in MaMNs was smaller than that of DiMNs and duration of the mAHP in NaMNs was shorter than that of DiMNs. Decay time constant of the mAHP tail current in MaMNs was shorter than that in DiMNs. Ca^<2+> influx producing the mAHP through activation of Ca^<2+>-activated K^+ channel was monitored using Ca^<2+> imaging, in the presence of apamin ? -agatoxin IVA, ? -conotoxin CV1A and Ni^<2+>. The slope of the relationship between firing frequency (f) and membrane depolarization (V) induced by injection of 1-s current pulses was steeper in MaMNs than the slope in DiMNs. The slope of the f-V relationship were correlated with amplitude and duration of the mAHP and the difference in the slope of the f-V relationship between MaMNs and DiMNs was abolished by apamin. We conclude that smaller and shorter mAHP in MaMNs results in steeper slope of the the f-V relationship, compared with DiMNs. Such firing properties of jaw-closing and opening motoneurons might contribute to transduction of masticatory drive signal from central pattern generator of mastication to appropriate activities of jaw-closing and opening muscles.
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