Effect of calcium ion on the release of gamma-aminobutyric acid from synaptosomal fraction

Brain synaptosomes released endogenous gamma-aminobutyric acid (GABA) in response to Ca2+. The release of GABA in response to 2.5 mM Ca2+ increased linearly with logK+]0, showing that a membrane potential-dependent Ca2+ channel limits the GABA release. In the presence of Ca2+ ionophore, A23187, GABA release increased linearly with logCa2+]0 without altering the membrane potential of synaptosomes.