The differential effects of excitatory amino acids on uptake of 45CaCl2 by slices from mouse striatum.

Exposure to L-glutamate (10 mM) or 60 mM K+ for 1 min significantly stimulated the uptake of 45Ca2+ in slices from mouse striatum. Glutamate-induced stimulation was antagonized by 30 mM Mg2+ and by 5 or 10 mM L-glutamic acid diethyl ester, but not by 5 microM tetrodotoxin. Under these 1-min incubation conditions, neither kainate nor N-methyl-D,L-aspartate significantly affected the uptake of 45Ca2+ ion. By contrast, following preincubation for 10 min, glutamate and the conformationally restricted analogues, ibotenate, quisqualate, and kainate significantly inhibited the 60 mM K+-induced stimulation of the uptake of 45Ca2+. These effects of glutamate and kainate were not significantly affected by the presence of 1 mM Ca2+ in the preincubation medium. These results suggest that glutamate may activate a receptor directly linked to Ca2+ channels, whereas kainate may indirectly modulate the intracellular disposition of Ca2+.