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Molecular Pharmacology, Vol 10, 438-449, Copyright © 1974 by the American Society for Pharmacology and Experimental Therapeutics
-Aminobutyric Acid from Isolated Brain Synaptosomes
1 Department of Psychobiology, School of Biological Sciences, University of California,
Irvine, California 92664
The alkaline earths Ca++, Sr++, and Ba++ stimulated the secretion of [14C]
-aminobutyric
acid from isolated brain synaptosomes at various K+ and veratridine concentrations. K+ and
veratridine produced different orderings of alkaline earth secretion-stimulation efficacy. In
addition, La+++ stimulated release in the presence of either K+ or veratridine. Ca++ concentrations above physiological levels inhibited secretion in the presence of moderately elevated K+ concentrations, but not in Na+-free veratridine solutions. Tetrodotoxin inhibited
Ca++-stimulated secretion only when veratridine was present. Mn++ inhibited secretion in
the presence of either K+ or veratridine. These results agree well with comparable data from
the neuromuscular junction and the adrenal medulla. Consideration of differential membrane
permeability to divalent cations and differential interaction of the ions with intracellular
binding sites provides a rationale for the relatives efficacies of the alkaline earths.