1991 Fiscal Year Final Research Report Summary
Modulating Mechanisms of Neurotransmitter Release in Central Synapses --- Investigation by a Quantal Analysis
| Project/Area Number |
01480121
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Neurophysiology and muscle physiology
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| Research Institution | Kanazawa University |
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Principal Investigator |
YAMAMOTO Chosaburo Kanazawa University, Faculty of Medicine, Professor, 医学部, 教授 (50008231)
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| Co-Investigator(Kenkyū-buntansha) |
KAMIYA Haruyuki Kanazawa University, Faculty of Medicine, Instructor, 医学部, 助手 (10194979)
HIGASHIMA Masato Kanazawa University, Faculty of Medicine, Lecturer, 医学部, 講師 (00173146)
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| Project Period (FY) |
1989 – 1991
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| Keywords | synaptic transmission / modulator / quantal analysis / adenosine / baclofen / GABA / mossy fiber / hippocampal formation |
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| Research Abstract |
Information on release of neurotransmitter from central synaptic boutons can be obtained only by a rigorous quantal analysis. To establish a quantal analysis method in hippocampus, we developed a technique to activate a single mossy fiber, axon of granule cell, and record excitatory postsynaptic potentials (EPSPS) from a CA3 neuron innervated by the particular granule cell in thin transverse sections of the guinea pig hippocampus. The amplitude distribution of the unitary EPSPs recorded by this method was described by the Pascal statistics. The values of mean quantal content (m) and mean quantal amplitude (q) could be estimated by the maximum likelihood method.
Acetylcholine and-norepinephrine administered to the perfusing solution failed to induce reproducible changes in the unitary EPSPS.
Baclofen, an agonist of the GABA-B receptor, suppressed the unitary EPSPs reversibly. This suppression was accompanied by decreases in m (14% at 1 muM and 59% at 10 muM baclofen). The q value was decreased by 18% at 1 muM and by 21% at 10muM. These results indicate that the GABA-B receptor at the mossy fiber terminal modulates release of transmitter therefrom.
Adenosine suppressed the unitary EPSPs to 57% at 10 muM. Them value was reduced to 51% under the action of adenosine, while no significant changes were detected in q. From these results, it is concluded that the adenosine terminal exerts inhibitory modulating action on release of transmitter.
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