N-methyl-D-aspartate raises cytosolic calcium concentration in rat cerebellar granule cells in culture.

The effects of glutamate receptor agonists on cytosolic calcium concentration in freshly isolated cerebellar granule cells and cells maintained in short term culture were determined using the fluorescent indicator fura-2. In freshly isolated cells depolarisation with high-K+ or addition of N-methyl-D-aspartate (NMDA) had no or only small effects on cytosolic calcium. After cells had been grown in monolayer culture for 20 h marked increases in cytosolic calcium concentration in response to 25 mm K+ or NMDA were detected. Other glutamate agonists had no (quisqualate) or small (kainate) effects on cytosolic calcium concentration. NMDA elevated cytosolic calcium concentration in the absence or presence of Mg2+ both before and after depolarisation by high K+. The results suggest that the effect of NMDA on granule cell differentiation and survival could be mediated by elevation of cytosolic calcium levels.