2004 Fiscal Year Final Research Report Summary
Role of neurotransmitters and environmental enrichment in the critical period of brain development
| Project/Area Number |
14580733
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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 |
Nerve anatomy/Neuropathology
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| Research Institution | DOKKYO UNIVERSITY SCHOOL OF MEDICINE |
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Principal Investigator |
UEDA Shuichi DOKKYO UNIVERSITY, SCHOOL OF MEDICINE, PROFESSOR, 医学部, 教授 (60150570)
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| Co-Investigator(Kenkyū-buntansha) |
SAKAKIBARA Shin-ichi DOKKYO UNIVERSITY, SCHOOL OF MEDICINE, ASSISTANT PROFESSOR, 医学部, 助教授 (70337369)
NAKADATE Kazuhiko DOKKYO UNIVERSITY, SCHOOL OF MEDICINE, RESEARCH ASSOCIATE, 医学部, 助手 (80372895)
NODA Takahiro DOKKYO UNIVERSITY, SCHOOL OF MEDICINE, RESEARCH ASSOCIATE, 医学部, 助手 (90364596)
KOIBUCHI Noriyuki GUNMA UNIVERSITY, GRADUATE SCHOOL OF MEDICINE, PROFESSOR, 医学部, 教授 (80234681)
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| Project Period (FY) |
2002 – 2004
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| Keywords | dentate gyrus / proliferation / water maze / HPLC / BrdU / learning hehavior / Neurogenesis / serotonin |
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| Research Abstract |
ABSTRACT
The dentate gyrus(DG) of the hippocampal formation produces new neurons throughout adulthood in mammalian species. Several experimental statuses and factors regulating neurogenesis have been identified in the adult DG. For example, exposure to an enriched environment enhances neurogenesis in the DG and improves hippocampus-dependent spatial learning. Furthermore, serotonin is known to influence adult neurogenesis, and learning and memory. However, the effects of long-lasting depletion of serotonin over the developing period on the neurogenesis have not been investigated. Thus, we examined the influence of long-lasting serotonin depletion on the environmental enrichment-induced neurogenesis and spatial memory performance. As reported previously, environmental enrichment significantly increased new neurons in the DG. However, there was no improvement of spatial learning test in adult rats in standard and in environmental enrichment housings.
Intracisternal administration of the serotonergic neurotoxin, 5,7-dihydroxytryptamine (5,7-DHT), on postnatal day 3 apparently reduced serotonin content in the adult hippocampus without regeneration. This experimental depletion of serotonin in the hippocampus of rats housed in an enriched environment had no effect on spatial memory performance, but produced significant decreases in the number of bromodeoxyuridine (BrdU)-labeled new cells in the DG. These findings indicate that newly generated cells stimulated by environmental enrichment are not critical for improvements in hippocampus-dependent learning. Furthermore, numbers of BrdU-labeled cells in the DG of 5,7-DHT-injected rats did not differ between 1 day and 4 weeks after BrdU injection. These data suggest that survival of newly generated DG cells remains relatively constant under long-lasting serotonin depletion.
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