Synaptic localization of the 67,000 mol. wt isoform of glutamate decarboxylase and transmitter function of GABA in the mouse cerebellum lacking the 65,000 mol. wt isoform.

Subcellular localization of the 67,000 mol. wt isoform of glutamate decarboxylase and neurotransmitter function of GABA were investigated in the cerebellum of the mice lacking the 65,000 mol. wt isoform of glutamate decarboxylase. The GABA content decreased by 25% in the cerebellum. Putative GABA-releasing terminals from basket/stellate and Golgi cells were immunostained with glutamate decarboxylase-67 antibody. Basket cell-derived inhibitory postsynaptic currents in Purkinje cells and the high potassium-induced release of GABA were not significantly affected. Although previous investigations have suggested that glutamate decarboxylase-65 is mainly involved in transmitter synthesis and that glutamate decarboxylase-67 is transported to the nerve terminals only after association with glutamate decarboxylase-65, the present results indicate that glutamate decarboxylase-67 is independently concentrated in the nerve terminals and provides GABA for synaptic transmission in the absence of glutamate decarboxylase-65.