2001 Fiscal Year Final Research Report Summary
Role of neural cell adhesion molecule and neuronal activity in formation of the connection between the hippocampal mossy fibers and pyramidal cells
| Project/Area Number |
11680792
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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 |
Neuroscience in general
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| Research Institution | JUNTENDO UNIVERSITY |
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Principal Investigator |
SEKI Tasunori Juntendo University, School of Medicine, Assistant Professor, 医学部, 講師 (20175417)
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| Project Period (FY) |
1999 – 2001
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| Keywords | hippocampus / neuronal circuit / mossy fiber / neurogenesis / synapse formation / collateral / slice culture / 接着分子 |
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| Research Abstract |
It is well known that transient innervation and subsequent synapse elimination occur in several regions of the developing nervous system such as motor nerve endings, the connection between the cerebellar purkinje cells and climbing fibers. I propose the hypothesis that a similar mechanism functions in the synapses between the hippocampal mossy fibers and pyramidal cells, on the basis of our previous study using NCAM-180-deficient mice. In the present study, the postnatal development of the mossy fibers were observed in the rats, mice and NCAM-180- deficient mice at the age of 1 to 8 weeks. Fixed hippocampus were labeled with DiI and were observed by a confocal laser scanning microscopy and electron microscopy. Many collaterals arising from mossy fibers penetrated the CA3 pyramidal cell layer in 1- and 2-week-old rats and mice, and thereafter the number of the collaterals decreased. In these animals, the collaterals were arised from various sized boutons on the mossy fibers and the large boutons also had some filamentous extensions with bulbous endings. The collaterals invading the CA3 pyramidal cell layer form additional boutons en route and at the tips. The size of the boutons and the length of the extensions decreased in the 8- week-old rats and mice. However, the collaterals with the boutons remained in NCAM-180-mice at the age of 2 months. Further hippocampal slices from 5-day-old rats were cultured and labeled with DiI. The invading and retracting processes of the mossy fiber collaterals were observed in living hippocampal slices. The results support the view that the mossy fibers give rise to transient collaterals which could form transient synapses on the CA3 pyramidal cells and NCAM may involve this process.
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