gamma-Aminobutyric acid elevates cytosolic Ca in bovine chromaffin cells

Measurements of the cytosolic Ca concentration ([Ca]i) with the Ca-sensitive dye, fura-2, showed that in intact, but not in voltage-clamped, bovine chromaffin cells gamma-aminobutyric acid (GABA, 10 microM) elicited a transient increase in [Ca]i. The Ca transient of intact cells was inhibited by bicuculline (20 microM), by removal of extracellular Ca or by treatment with the Ca channel blocker cobalt (2.5 mM), and enhanced by lowering the extracellular Cl. We conclude, that GABA elevates [Ca]i by inducing a GABAA-receptor-linked Cl current which depolarizes the cell membrane sufficiently to activate potential-operated Ca channels and cause Ca entry into the cell.