Hypotension alters the release of catecholamines in the hypothalamus of the conscious rabbit.

The posterior hypothalamic nucleus of conscious, freely moving rabbits was superfused with CSF through a cannula. Intravenous injection of nitroprusside elicited a fall of the arterial blood pressure and increased the rates of release of endogenous catecholamines in the posterior hypothalamic nucleus, while noradrenaline increased the blood pressure but did not change the release of catecholamines. It is concluded that hypotension leads to a counteracting increase in the release of catecholamines in the posterior hypothalamus.