| Project/Area Number |
10680760
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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 | Gunma University, School of Medicine, Institute for Behavioral Science |
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Principal Investigator |
KUROMI Hiroshi Gunma University School of Medicine, Institute for Behavioral Science, Associate Professor, 医学部, 助教授 (30009633)
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| Co-Investigator(Kenkyū-buntansha) |
YOSHIHARA Motojiro Gunma University School of Medicine, Institute for Behavioral Science, Assistant Professor, 医学部, 助手 (80222397)
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| Project Period (FY) |
1998 – 1999
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| Project Status |
Completed (Fiscal Year 1999)
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| Budget Amount *help |
¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 1999: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1998: ¥2,200,000 (Direct Cost: ¥2,200,000)
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| Keywords | synaptic vesicles / FM1-43 / exo / endo cycling pool / reserve pool / stimulation frequency / cAMP / PKA cascade / rutabaga / dunce / quantal content / forskolin / cyclosporin A |
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| Research Abstract |
In a temperature-sensitive Drosophila mutant, shibire, synaptic vesicles are completely depleted in nerve terminals after stimulation at 34゜C, but upon returning to 22゜C endocytosis resumes. In this study synaptic vesicles in the boutons of nerve terminals at the mutant neuromuscular junction were loaded with a fluorescent dye, FM1-43, during vesicle reformation at 22゜C after complete depletion at 34゜C. We found two distinct pools of synaptic vesicles, namely an exo/endo cycling pool, located in the periphery of the bouton and a reserve pool, located in its center. Cytochalasin D treatment eliminated the reserve pool and reduced synaptic transmission evoked by high frequency stimulation. Thus the reserve pool may play a crucial role for sustaining high frequency synaptic transmission. To determine the role of exo/endo cycling vesicle pool in synaptic transmission, we estimated the quantal content electrophysiologically while the pool size was determined optically using fluorescent dye
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FM1-43. We then manipulated the size of the pool with following treatments. First, to change the state of boutons of terminals motoneuronal axons were severed. With this treatment the size of exo/endo cycling vesicle pool decreased together with the quantal content. Secondly, we promoted the FM1-43 uptake using cyclosporin A which inhibits calcineurin activities and enhances endocytosis. Cyclosporin A increased the total uptake of FM1-43, but neither the size of exo/endo cycling vesicle pool nor the quantal content changed . Thirdly, we increased the size of exo/endo cycling vesicle pool by forskolin which enhances synaptic transmission. The forskolin-treatment increased both the size of exo/endo cycling vesicle pool and the quantal content. Thus, we found that the quantal content was closely correlated with the size of exo/endo cycling vesicle pool but not necessarily with the total uptake of FM1-43 fluorescence by boutons. The results suggest that vesicles in the exo/endo cycling pool primarily participate in evoked exocytosis of vesicles. Less
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