The effect of Ca2+ on the pharmacological specificity of [3H]glutamate binding sites in rat hippocampus.

The inhibition of [3H]glutamate binding to rat hippocampal membranes by various compounds was measured. L-Glutamic, L-2-amino-4-phosphonobutyric and 4-fluoroglutamic acids had similar IC50 values (2.12 microM, 4.98 microM and 3.90 microM respectively). D-Glutamate and D-2-amino-4-phosphonobutyrate were less potent than L-glutamate (IC50S 18.9 microM and 46.5 microM respectively) and L-glutamate diethylester (IC50 519 microM) was the weakest inhibitor tested. Addition of 10 mM CaCl2 caused a 2.27-fold increase in displaceable binding but did not alter the IC50 values of any of the inhibitors tested.