The effect of penicillin on the release of gamma-aminobutyric acid from cerebral cortex slices.

Penicillin is known to block the depressant action of GABA on cortical and spinal neurons. In this study we examined the effect of penicillin on the release of endogenous amino acids from rat cerebral cortex slices. The principal finding was that penicillin blocked the potassium-stimulated release of GABA, a calcium-dependent process. It did not block the veratridine-stimulated release of GABA, a calcium-independent process. It did not affect the release of other putative transmitter amino acids. Inhibition of GABA release from nerve endings may explain in part the ability of penicillin to depress synaptic inhibitory mechanisms.