[Effects of arterial blood pressure change on release of GABA in the posterior hypothalamus conscious of freely moving rats].

Push-pull superfusion technique was used to investigate the release of endogenous gamma-aminobutyric acid (GABA) in the posterior hypothalamus of the conscious, freely moving rat in response to peripherally applied drugs or experimentally induced blood pressure changes. The rise in blood pressure elicited by intravenous infusion of phenylephrine (15 micrograms.kg-1.min-1) or blood (3 ml/100 g) was associated with an increased rate of GABA release in the posterior hypothalamus. Hypotension produced by nitroprusside (30 micrograms.kg-1.min-1), chlorisondamine (3 mg.kg-1,iv) and controlled bleeding (3 ml/100 g) led to a counteracting decrease in hypothalamic GABA outflow. This finding suggests that GABAergic neurons of the conscious, freely moving rat in the posterior hypothalamus are involved in cardiovascular control and possess a hypotensive function.