CARDIOVASCULAR EFFECTS OF INTRACEREBROVENTRICULAR NOREPINEPHRINE IN CONSCIOUS AND ANESTHETIZED MONKEYS

Norepinephrine, infused into the third cerebral ventricle of 7 restrained, unanaesthetized rhesus monkeys, evoked dose-related increases in systemic arterial pressure at each of three different (30 sec, 5 min or 1 hr) infusion times and rates. Anaesthetic doses of sodium pentobarbital blocked, but did not reverse, the presser response. A series of 6-hydroxydopamine injections (31 mg over an 11-day period) given centrally to 3 monkeys led to a steady reduction of basal blood pressures and pulse rates (-18 and -16 mm Hg systolic and diastolic and -34 beats/min during the second week after the last injection) and blocked the effects of centrally, but not intravenously, administered norepine- phrine. The monkeys had intense sympathomimetic response to the initial injection of 1 mg of 6-hydroxydopamine, but became progressively tachyphylactic to subsequent higher doses. The results suggest that noradrenergic nerves near the lateral and third ventricles of primates play an important role in controlling both acute and chronic levels of systemic arterial blood pressure. © 1978.