2002 Fiscal Year Final Research Report Summary
Termination mechanisms of the critical period in visual cortex
| Project/Area Number |
13480265
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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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 | Nagoya University |
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Principal Investigator |
KOMATSU Yukio Nagoya University, Research Institute of Environmental Medicine, Professor, 環境医学研究所, 教授 (90135343)
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| Co-Investigator(Kenkyū-buntansha) |
YOSHIMURA Yumiko Nagoya University, Research Institute of Environmental Medicine, Assistant Professor, 環境医学研究所, 助手 (10291907)
KUROTANI Tohru Nagoya University, Research Institute of Environmental Medicine, Associate Professor, 環境医学研究所, 講師 (50195591)
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| Project Period (FY) |
2001 – 2002
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| Keywords | plasticity / critical period / long-term potentiation / visual cortex / excitatory synapse / T type Ca channel / development / gene expression |
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| Research Abstract |
Selective responsiveness of visual cortical cells develops experience-dependently during the critical period. However, dark rearing prolongs that period into adulthood. We found that a two Hz stimulation applied to layer 4 induced long-term potentiation (LTP) at excitatory synapses in rat visual cortical layer 2/3 pyramidal cells, which required the activation of Ni^<2+>-sensitive, presumably T type, Ca^<2+> channels but not NMDA receptors. This NMDA receptor-independent LTP occurred only during the critical period, suggesting that it could underlie the experience-dependent development. To elucidate the termination mechanism of the critical period, we investigated experience dependence of this LTP. In rats reared in darkness from birth into adulthood, LTP occurred as frequently as in rats during the critical period. This maintained high incidence of LTP was abolished by a light exposure of only two days. The amplitude of T-type Ca^<2+> channel currents recorded from layer 2/3 pyramidal
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cells decreased significantly from young to adult rats. This reduction was prevented by dark rearing and completed by a following short exposure to light. This suggests that the age and experience-dependent changes in LTP is mostly ascribed to those in T type Ca^<2+> channels. We, then, tested whether the termination of the critical period requires mRNA synthesis. Before exposure of dark-reared rats to light for 2 days, acontinuous injection of RNA synthesis inhibitor actinomycin D into one side of visual cortex was started using an osmotic minipump. LTP was not induced in slices obtained from the non-injected hemisphere, whereas it occurred in slices obtained from the injected hemisphere. It is likely that LTP production was inhibited by some molecules newly synthesized in response to the visual experience, or synthesis of some molecules necessary for LTP production was inhibited. These results suggest that termination of the critical period requires mRNA synthesis triggered by visual experience. Less
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Research Products
(4 results)
