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AN ANALYSIS OF SOME FACTORS INFLUENCINGα‐ADRENOCEPTOR FEED‐BACK AT THE SYMPATHETIC JUNCTION IN THE RAT HEART
Author(s) -
DOCHERTY J.R.,
McGRATH J.C.
Publication year - 1979
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1979.tb16097.x
Subject(s) - sympathetic nervous system , medicine , endocrinology , blood pressure
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.