GABA Potentiates Potassium-stimulated 3H-dopamine Release from Slices of Rat Substantia Nigra and Corpus Striatum

GABA (10-5--10-3 M) had no effect on the spontaneous outflow of previously accumulated 3H-DA or 3H-5HT from rat nigral or striatal slices. However, GABA markedly potentiated the potassium-stimulated release of 3H-DA in both brain regions, while the depolarization-induced output of 3H-5HT was only slightly increased. This action of GABA was blocked by pictotoxin but not by bicuculline. Amphetamine likewise evoked a dose-related efflux of 3H-DA and 3H-5HT from nigra and striatum, but these releases were unchanged by GABA. The data suggest that GABA acts presynaptically in these areas to regulate dopaminergic cell function.