CENTRALLY INDUCED HYPOTENSION AND BRADYCARDIA AFTER ADMINISTRATION OF α‐METHYLNORADRENALINE INTO THE AREA OF THE NUCLEUS TRACTUS SOLITARII OF THE RAT

Abstract

In anaesthetized rats, bilateral injections of α‐methylnoradrenaline, noradrenaline or adrenaline into the area of the nucleus tractus solitarii (NTS) of the brain stem caused dose‐dependent decreases of systemic arterial blood pressure and heart rate. The effects of α‐methylnoradrenaline were most pronounced and lasted longest. The cardiovascular effects of α‐methylnoradrenaline appeared to be restricted to the medio‐caudal part of the NTS. Prior administration of the α‐adrenoceptor blocking agent, phentolamine, reversed the fall in blood pressure and heart rate induced by α‐methylnoradrenaline into an increase. Systemic administration of atropine combined with vagotomy potentiated the inhibitory effects of α‐methylnoradrenaline on the cardiovascular system. 1976 British Pharmacological Society