Specificity of GABA as a stimulator of dopamine release in rat substantia nigra

The effects of amino acids and the benzodiazepine, flurazepam, on spontaneous and potassium-stimulated [3H]dopamine (DA) release were studied in slices of rat substantia nigra. None of the amino acids tested liberated [3H]DA directly. Flurazepam increased [3H]DA output by 51% and this effect was partially blocked by bicuculline but not by picrotoxin. GABA, L-glutamate and flurazepam, but none of the other compounds, potentiated the release of [3H]DA evoked by 20 mM KCl. The facilitation produced by flurazepam, but not by GABA or L-glutamate, was weakly antagonized by bicuculline and not picrotoxin. GABA did not modify the efflux of [3H]DA induced by low Na+, veratridine, ouabain, calcium ionophore A 23187, amphetamine or exogenous DA.