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PRESYNAPTIC EFFECT OF CLONIDINE ANTAGONIZED BY THE TETRAMINE DISULPHIDE, BENEXTRAMINE
Author(s) -
BELLEAU B.,
BENFEY B.G.,
MELCHIORRE C.
Publication year - 1982
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.1476-5381.1982.tb09182.x
Subject(s) - phentolamine , clonidine , medicine , endocrinology , stimulation , chemistry , adrenergic receptor , receptor
1 The presynaptic α‐adrenoceptor blocking activity of the newly synthesized α‐adrenoceptor blocking drug, benextramine, was evaluated in the isolated left atrium of the guinea‐pig heart. 2 High‐voltage stimulation increased the force of contraction of electrically driven atrial strips, presumably by releasing noradrenaline from sympathetic nerve endings. Like phentolamine, benextramine increased the effect of high‐voltage stimulation, presumably by blocking presynaptic α‐adrenoceptors. 3 Clonidine reduced the effect of high‐voltage stimulation, presumably by stimulating presynaptic α‐adrenoceptors. The inhibitory effect of clonidine was antagonized noncompetitively by benextramine and competitively by phentolamine. 4 Combined administration of benextramine and phentolamine only resulted in the competitive phentolamine antagonism. Thus phentolamine protected the presynaptic α‐adrenoceptors against benextramine blockade.