Muscimol Potentiation of Acidic Amino Acid Release from Cerebellar Synaptosomes Is Chloride Dependent

Abstract
The depolarization-induced release of preaccumulated acidic amino acids and newly synthesized glutamate from [rat] cerebellar synaptosomal preparations is potentiated by GABA agonists through a GABAergic presynaptic mechanism. A systematic analysis of the ionic requirements of the potentiating effect of muscimol on the high K+-evoked release of D-[3H]aspartate is reported. Ca2+, Na+ and Mg2+ are not required for muscimol to exert its effect; a depolarizing concentration of K+ is a necessary, but not sufficient, condition to observe the presynaptic effect in question; and a minimal Cl- concentration (50-70 mM) is also required. A possible model based on these findings is proposed.

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