A study of hypertension: participation of central adrenaergic mechanism on the angiotensin II-induced hypertension.

I. Interactions of angiotensin II and norepinephrine in the rat hypothalamus and other brainstem were studied by intraventricular perfusion or/and intravenous administration. (1) Intravenous administration of angiotensin reduced the hypothalamus norepinephrine content. (2) Intraventricularly perfused angiotensin reduced the hypothalamus norepinephrine but did not alter that in other parts of brainstem. Hypothalamus norepinephrine was reduced more by intravenous administration of angiotensin than by intraventricularly perfused angiotensin. II. The involvements of adrenergic mechanism in the central pressor effect of angiotensin II were studied through observation of blood pressure changes following injection of angiotensin II, phentolamine and propranolol into the rabbit lateral ventricle of rabbit brain.(1) Intraventricular administration of phentolamine suppressed the central mediated pressor respons of angiotensin. (2) Simultaneous intraventricular administration of propranolol enhanced the angiotensin pressor effect in anesthetized rabbits.