RT Journal Article SR Electronic T1 Effects of Polyvalent Cations on Stimulus-Coupled Secretion of [14C]-γ-Aminobutyric Acid from Isolated Brain Synaptosomes JF Molecular Pharmacology JO Mol Pharmacol FD American Society for Pharmacology and Experimental Therapeutics SP 438 OP 449 VO 10 IS 3 A1 WILLIAM B. LEVY A1 JOHN W. HAYCOCK A1 CARL W. COTMAN YR 1974 UL http://molpharm.aspetjournals.org/content/10/3/438.abstract AB The alkaline earths Ca++, Sr++, and Ba++ stimulated the secretion of [14C]γ-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.