Effects of lowering [Na+]o and [K+]o and of ouabain on quisqualate-induced ionic changes in area CA1 of rat hippocampal slices.

Changes in extracellular ([Na+]o) and calcium ([Ca2+]o) concentration evoked by quisqualate (Quis), applied iontophoretically, were measured in rat hippocampal slices. Following an initial decrease in [Ca2+]o, Quis causes a post-application overshoot, which may reflect Ca2+ extrusion from cells by the Na+/Ca2+ exchanger. To test this hypothesis, the effects of directly and indirectly reduced transmembrane Na+ gradients on these Quis-induced Ca2+ overshoots were investigated. In all cases the post-application overshoots were reduced. This suggests that the Na+/Ca2+ exchanger is involved in the production of these Quis-induced Ca2+ overshoots which may have important implications for understanding how various types of glutamate receptors differ in their capability to trigger Ca2(+)-activated processes.