| Project/Area Number |
08680877
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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 |
神経・脳内生理学
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| Research Institution | Asahikawa Medical College |
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Principal Investigator |
TAKAKUSAKI Kaoru Asahikawa Medical College Department of Physiology.Instructor, 医学部, 講師 (10206732)
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| Project Period (FY) |
1996 – 1997
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| Project Status |
Completed (Fiscal Year 1997)
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| Budget Amount *help |
¥2,500,000 (Direct Cost: ¥2,500,000)
Fiscal Year 1997: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1996: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Keywords | Postural muscle tone / Generalized Motor Inhibition / Spinal interneurons / Flexor reflex afferents / Postsynaptic inhibition / Presynaptic inhibition / Ca channel / Rhythmic firing / シナプス機構 / 分子機構 / リズム発生機序 / 歩行運動 |
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| Research Abstract |
This study was aimed at elucidating the spinal interneuronal mechanisms involved in the generalized motor inhibition produced by stimulating the medullary reticular formation (MRF). Changes in the excitability of hindlimb alpha-motoneurons (MNs), interneuronal transmission of reflex pathways to MNs, interneurons (INs) in reflex pathways and primary afferent terminals in lumbosacral segments (L5-S1) were examined before and after the MRF stimulations in acute decerebrate cats.
Seventy-six cats weighing of 2.1-4.3 kg were decerebrated at precollicular-postmammilarly level. The MRF stimulation induced inhibitory postsynaptic potentials (IPSPs) in both extensor and flexor MNs innervating hindlimb muscles as well as most INs mediating reciprocal Ia inhibition, non-reciprocal group I inhibition, recurrent inhibition, and flexor reflex afferent (FRA) pathways. It also produced primary afferent depolarization (PAD) of Ia, Ib and cutaneous afferent fibers. Both the IPSPs in MNs and INs, and the
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PAD in primary afferents were suppressed by volleys in FRA.However, the MRF stimulation excited INs that received inhibition from FRA.One-fourth of them also received monosynaptic excitation from group I afferent. These INs were located in ventro-medial portion of lamina VII.Spike-triggered averaging revealed that they produced monosynaptic IPSPs in MNs as well as INs, and produced PAD in primary afferents.
These results suggest that the generalized motor inhibition is due to not only the postsynaptic inhibition of MNs and INs interposed in reflex pathways but also suppression of excitability of primary afferent terminals. Such inhibitory effects are possibly mediated by INs receiving excitatory MRF input and inhibitory FRA input. The results also proposed the co-inhibitory interaction at spinal interneuronal level between the medullary reticulospinal pathway and FRA pathways. It may operate as a functional gate that integrate descending signals from higher motor centers and peripheral sensory signals to modify ongoing movements. Less
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