Endogenous GABA potentiates the potassium-induced release of dopamine in striatum of the freely moving rat: A microdialysis study

Using microdialysis, a study was made of the effects of an Increase of endo genous GABA on basal and potassium-stimulated release of dopamine in striat um of the awake rat. The dopamine metabolites DOPAC and HVA were also measu red. Extracellular concentrations of GABA were increased by inhibiting its uptake with nipecotic acid. TTX (10 mu M) reduced basal extracellular conce ntrations of dopamine, and dopamine metabolites, but not GABA. Nipecotic ac id (200, 500, and 1000 mu M) produced a dose-related increase in basal extr acellular concentrations of GABA, but did not change basal extracellular co ncentrations of dopamine and dopamine metabolites. However, nipecotic acid significantly enhanced the dopamine release produced by perfusion of potass ium (50 mM) and also enhanced the extracellular increase of GABA produced b y high potassium. These results suggest that an increase of endogenous GABA is facilitating the stimulated release, but not the basal release, of dopa mine in the striatum of the awake rat. (C) 1999 Elsevier Science Inc.