GABA augments basal and electrically stimulated 3H-norepinephrine release in hypothalamic, preoptic area and cortical slices of female rats.

These studies examined the regulation by GABA of norepinephrine release from hypothalamus, preoptic area and frontal cortex. Using superfused brain slices from female rats, we show that 100 microM GABA enhances both basal and electrically stimulated release of 3H-norepinephrine in all three brain regions. The GABAA agonist muscimol (100 microM) significantly augments 3H-norepinephrine release, but it is somewhat less effective than GABA. The GABAB agonist baclofen has little or no effect on basal 3H-norepinephrine efflux. GABA also augments both the magnitude and duration of electrically evoked 3H-norepinephrine release in slices from all three brain regions. GABA facilitation of electrically stimulated 3H-norepinephrine release is mediated through GABAA receptors as evidenced by its blockade by 10 microM bicuculline, a GABAA antagonist, but not by 200 microM 2-OH-saclofen, a GABAB antagonist. These data show that the inhibitory amino acid neurotransmitter GABA enhances both basal and evoked release of 3H-norepinephrine in brain slices from female rats. These effects are predominantly mediated by GABAA receptors. GABA modulation of hypothalamic norepinephrine release may play a role in the regulation of gonadotropin secretion and reproductive behaviors such as lordosis.