Oestrogen and noradrenaline modulate endogenous GABA release from slices of the rat medial preoptic area

Endogenous gamma-aminobutyric acid (GABA) release from the rat medial preoptic area (MPOA) was measured in an in vitro slice technique with sensitive HPLC analysis. Oestrogen is demonstrated to increase GABA activity in the ovariectomised, oestrogen-primed (OVX-EB) rat prior to the luteinising hormone (LH) surge compared with ovariectomised (OVX) animals. Noradrenaline (NA) at a concentration of 10 microM was found to significantly enhance GABA release in response to 30 mM potassium stimulation in both OVX and OVX-EB animals. A significantly greater response to NA was observed in the OVX-EB animal. No effect of NA on basal GABA release was detected. The effects of NA were blocked by the alpha-adrenergic receptor blocker phenoxybenzamine (PB). These data suggest that GABA activity is modulated both by oestrogens and noradrenergic-mediated input in the MPOA.