Abstract
The ionotropic glutamate receptor delta2 subunit (GluRdelta2), which is selectively expressed at a parallel fiber-Purkinje neuron (pf-PN) synapse, plays critical roles in the long-term depression and formation of synaptic connections in the cerebellum. Previous study on the mutant mice deficient in GluRdelta2 (delta2 mice) showed that the long-term depression of pf-PN synaptic transmission is impaired, a PN is innervated by multiple climbing fibers and the frequency of climbing fiber input is increased. Here, we examined the GABAergic synaptic inhibition on a PN in the delta2 mice. We found pronounced enhancement of excitation propagation by application of bicuculline (a GABA(A) receptor antagonist) in the molecular layer of cerebellar slice preparation prepared from a delta2 mouse, suggesting the enhanced GABAergic inhibition in the mutant mouse. Whole-cell patch clamp experiments on PNs in slice preparations revealed that amplitudes of miniature IPSCs (mIPSCs) were larger in delta2 mice than in wild type mice. We also found that depolarization induced potentiation (rebound potentiation, RP) was not induced in slices prepared from delta2 mice. These results suggest that enhancement of climbing fiber inputs induces and saturates RP in delta2 mice. [Jpn J Physiol 54 Suppl:S142 (2004)]
