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THE ACTION OF CLONIDINE ON ISOLATED ARTERIAL PREPARATIONS
Author(s) -
Hodge RL,
Robinson SM
Publication year - 1972
Publication title -
australian journal of experimental biology and medical science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.999
H-Index - 104
eISSN - 1440-1711
pISSN - 0004-945X
DOI - 10.1038/icb.1972.44
Subject(s) - clonidine , contraction (grammar) , denervation , adrenergic receptor , medicine , endocrinology , receptor , sympathetic denervation , chemistry , vascular smooth muscle , adrenergic , blood vessel , mechanism of action , alpha (finance) , smooth muscle , in vitro , biochemistry , surgery , construct validity , patient satisfaction
Summary Isolated perfused rabbit ear and rat tail arteries as well as helical strips from the latter have been used in this study to ascertain the mechanism of clonidine's vasoconstrictor action. It was found that the drug constricted the perfused arteries and that this effect was abolished by adrenergic alpha receptor blockade. From a series of concentration response curves in these perfused arteries it was also determined that the intraluminal to extraluminal concentration ratios for clonidine were not significantly affected by chronic sympathetic denervation or cocaine pretreatment. In contrast, these procedures considerably augmented the response to extraluminal noradrenaline and caused a tenfold increase in the intraluminal to extraluminal concentration ratio. These findings indicate that the drug acts on alpha receptors in vascular smooth muscle and that this action is not dependent on sympathetic nerves. The maximum contraction of rat tail artery strips following clonidine application was only 25% of that produced by noradrenaline. An adrenergic alpha receptor blocking effect of the drug on this preparation was also demonstrated.