| Budget Amount *help |
¥92,400,000 (Direct Cost: ¥92,400,000)
Fiscal Year 2004: ¥22,400,000 (Direct Cost: ¥22,400,000)
Fiscal Year 2003: ¥22,400,000 (Direct Cost: ¥22,400,000)
Fiscal Year 2002: ¥22,400,000 (Direct Cost: ¥22,400,000)
Fiscal Year 2001: ¥25,200,000 (Direct Cost: ¥25,200,000)
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| Research Abstract |
Synaptic plasticity is the long-lasting alteration of transmission efficacy at a synapse, and has been a candidate cellular mechanism for learning and memory. Purkinje cells, sole neurons sending outputs from the cerebellar cortex, show several types of synaptic plasticity. One is the long term depression at excitatory synapses and another is the rebound potentiation at inhibitory synapses, which have been regarded as basic mechanisms for motor learning. In this study, we have been trying to elucidate the molecular mechanisms of induction, maintenance and regulation of the synaptic plasticity, and also to clarify its roles in regulation of information processing in the cerebellum and in the control of animal behavior. At inhibitory synapses we discovered the novel regulation mechanism of synaptic plasticity: the synaptic activity suppresses the induction of rebound potentiation. We also clarified molecular mechanism of that regulation. At excitatory synapses we found that calcineurin, calcium-dependent phosphatase, is implicated in the induction of late phase of long term depression. Further, we have also studied the behavior of mutant mice deficient in the ionotropic glutamate receptor δ 2 subunit, which is selectively expressed at excitatory synapses on a Purkinje cell and is necessary for the induction of long term depression. We showed that the mutant mice failed to perform adaptive modifications of reflex eye movements, which are models of motor learning. We also showed that the motor control ability of the mutant mouse was impaired more severely than that of lurcher mutant mouse, which lose all Purkinje cells during development. We analyzed the cause of sever motor discoordination and demonstrated that the δ2 subunit deficiency produces the oscillating activity in Purkinje cells by enhancing climbing fiber inputs, causing surplus movement and affecting motor control worse than no signal at all.
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