Glutamate stimulates release of Ca2+ from internal stores in astroglia

We report here that, in the absence of external Ca2+, glutamate produces a transient increase in intracellular Ca2+ [( Ca2+]i) in cultured spinal cord astrocytes, by mobilizing internal Ca2+ stores. [Ca2+]i was measured with Fura-2 using the ratiometric method. Astrocytes were identified by immunostaining for glial fibrillary acidic protein. Glutamate and quisqualate consistently caused a transient increase in [Ca2+]i, with both the response amplitude and latency being graded functions of agonist concentration. Some cells produced multiple transients. N-Methyl-D-aspartate, kainate and aspartate were ineffective. We conclude that the quisqualate subtype of glutamate receptors mediates release of Ca2+ from internal stores in mammalian astrocytes.