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

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Abstract
1 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. 2 The cardiovascular effects of α-methylnoradrenaline appeared to be restricted to the medio-caudal part of the NTS. 3 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. 4 Systemic administration of atropine combined with vagotomy potentiated the inhibitory effects of α-methylnoradrenaline on the cardiovascular system.