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An investigation of presynaptic α‐adrenoceptor subtypes in the pithed rat heart and in the rat isolated vas deferens
Author(s) -
Docherty James R.
Publication year - 1984
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.1476-5381.1984.tb16437.x
Subject(s) - vas deferens , endocrinology , medicine , chemistry
1 The presynaptic cardio‐inhibitory effects of the α‐adrenoceptor agonists xylazine, cirazoline and amidephrine and their interaction with the antagonists yohimbine and prazosin were investigated in the pithed rat. 2 The presynaptic inhibitory effects of the α 2 ‐selective agonist xylazine were antagonized by the α 2 ‐antagonist yohimbine but not by the α 2 ‐antagonist prazosin, thus demonstrating the lack of α 2 ‐adrenoceptor antagonism by prazosin. 3 The presynaptic inhibitory effects of cirazoline were antagonized equally by yohimbine and prazosin, and the presynaptic inhibitory effects of the selective α 1 ‐agonist amidephrine were antagonized by prazosin more potently than by yohimbine. 4 In the nifedipine‐treated isolated epididymal portion of the rat vas deferens, both xylazine and amidephrine produced concentration‐dependent inhibition of the isometric contraction to single pulse electrical stimulation. The α 2 ‐antagonist rauwolscine antagonized the inhibitory effects of xylazine but not of amidephrine. 5 It is concluded that inhibitory α 1 ‐adrenoceptors, as well as the already established α 2 ‐receptors, are present presynaptically in the pithed rat heart and in the rat vas deferens.