IDENTIFICATION OF KAINATE RECEPTOR-MEDIATED INTRACELLULAR CALCIUM INCREASES IN CULTURED RAT CEREBELLAR GRANULE CELLS

The functional expression of the kainate subtype of glutamate receptor (GluR) has been investigated in cultured rat cerebellar granule cells using single cell intracellular calcium ([Ca2+](i)) measurements. Bot h AMPA- and kainate-induced [Ca2+](i) increases could be blocked compl etely by the AMPA receptor-selective antagonist LY300168 (50 mu M). Ho wever, following treatment with concanavalin A, an inhibitor of kainat e receptor desensitisation, 30% of cells showed a kainate-induced [Ca2 +](i) rise of >100 nM in the presence of LY300168. Responses to 30 mu M kainate in the presence of LY300168 were virtually abolished by the AMPA and GluR5 kainate receptor competitive antagonist LY293558 (100 m u M). These results demonstrate the presence of functional kainate rec eptors on cultured cerebellar granule cells, and suggest that the GluR 5 subtype of kainate receptor plays a significant role in kainate rece ptor mediated [Ca2+](i) increases.