Localization of central noradrenergic mechanisms in cardiovascular regulation in rats.

1. Various drugs were injected stereotactically into the brain of anaesthetized rats. 2. Noradrenaline injected into the area of the nucleus of the tractus solitarius in the lower brain stem or into the far anterior hypothalamus/pre-optic region induced a fall in blood pressure and heart rate related to the administered dose. 3. When injected into the anterior hypothalamus/pre-optic region, clonidine and alpha-methylnoradrenaline induced a long-lasting decrease in blood pressure and heart rate.