AN ANALYSIS OF SOME FACTORS INFLUENCINGα‐ADRENOCEPTOR FEED‐BACK AT THE SYMPATHETIC JUNCTION IN THE RAT HEART

• Published in: British journal of pharmacology Vol. 66; no. 1; pp. 55 - 63
• Main Authors: DOCHERTY, J.R., McGRATH, J.C.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.05.1979; Nature Publishing Group
• Subjects: Adrenalectomy; Animals; Clonidine - pharmacology; Cocaine - pharmacology; Electric Stimulation; Feedback; Heart - innervation; Heart Rate - drug effects; Male; Neuromuscular Junction - physiology; Norepinephrine - pharmacology; Rats; Receptors, Adrenergic - physiology; Receptors, Adrenergic, alpha - physiology; Sympathetic Nervous System - physiology; Yohimbine - pharmacology
• ISSN: 0007-1188; 1476-5381
• DOI: 10.1111/j.1476-5381.1979.tb16097.x

1 The effects of the selective prejunctional α‐adrenoceptor antagonist, yohimbine, on the cardio‐acceleration responses to sympathetic stimulation were examined in the pithed rat. 2 Yohimbine reversed the inhibitory effects of the α‐adrenoceptor agonist, clonidine. on the stimulation‐induced tachycardia. 3 Yohimbine failed to potentiate significantly responses to stimulation in the absence of clonidine when stimulation was applied at the optimal level for cardiac responses (C6‐T1). 4 When the pithing rod electrode was moved to T2‐T6, cardioaccelerator responses were smaller and yohimbine produced potentiation at frequencies of ≥ 1 Hz. This potentiation was prejunctional since responses to exogenous noradrenaline (NA) were not increased by yohimbine. 5 In the presence of cocaine, potentiation by yohimbine could be shown at the lower frequency of 0.1 Hz. 6 The possible physiological significance of a negative feed‐back effect of noradrenaline on cardiac sympathetic nerves is discussed.