抄録
The cerebellum plays critical roles in motor control and learning. Relative simplicity of the cerebellar cortical circuit has prompted the study on how it works, which has made the cerebellum one of the best characterized structure of central nervous system. However, respective role of each component or its function such as a particular type of synapse, neuron or synaptic regulation has been elusive. We have been addressing these issues using several types of mutant mice, and here I present our recent data on the GluRδ2 (glutamate receptor δ2 subunit) knockout mice (δ2-/-). GluRδ2 is a molecule related to ionotropic glutamate receptor, which is specifically expressed at parallel fiber (PF)–Purkinje neuron (PN) synapses. The δ2-/- show impairment in the long-term depression, synaptic stabilization of PF-PN synapses and elimination of surplus climbing fiber (CF) inputs resulting in the multiple innervation to a PN, and also show motor discoordination and motor learning failure. We studied the eye movements and found that δ2-/- show involuntary spontaneous eye movements and large phase delay in the optokinetic response (OKR). We have been analyzing the mechanism of these abnormal motor regulations by simultaneous recording of eye movements and PN activity. Our results suggest that the enhanced CF activity in δ2-/- largely disturbed the normal pattern of PN activity regulating eye movement, that highlights the importance of synaptic inputs balance on a PN in motor regulation. [J Physiol Sci. 2006;56 Suppl:S44]
