[Ca2+]i regulation by glutamate receptor agonists in cultured chick retina cells

The effect of glutamate receptor agonists on the intracellular free calcium concentration ([Ca2+]i), measured with Indo-1, was studied in populations of cultured chick embryonic retina cells. The agonists of the ionotropic glutamate receptors, N-methyl-D-aspartate (NMDA), kainate, and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) increased the [Ca2+]i through a composite effect, comprising Ca2+ permeating the receptor-associated channels, and Ca2+ entering through voltage-gated Ca2+ channels. Furthermore, the [Ca2+]i responses to NMDA and AMPA also involved Ca2+ release from intracellular stores, which could not be mobilized by stimulation of the metabotropic receptor.