Effects of exogenous adrenaline and noradrenaline on vascular postsynaptic alpha 1- and alpha 2-adrenoceptors in man

The effects of adrenaline and noradrenaline on vascular postsynaptic alpha 1- and alpha 2-adrenoceptors were investigated in six healthy volunteers. The catecholamines were infused intra-arterially, in three cumulative doses, together with a continuous infusion of saline, doxazosin (alpha 1-selectiv...

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Bibliographic Details
Published in:	Journal of hypertension. Supplement Vol. 2; no. 3; p. S119
Main Authors:	Jie, K, van Brummelen, P, Vermey, P, Timmermans, P B, van Zwieten, P A
Format:	Journal Article
Language:	English
Published:	England 01-12-1984
Subjects:	Adult Blood Vessels - drug effects Dose-Response Relationship, Drug Doxazosin Epinephrine - pharmacology Forearm - blood supply Humans Male Norepinephrine - pharmacology Prazosin - analogs & derivatives Prazosin - pharmacology Receptors, Adrenergic, alpha - drug effects Regional Blood Flow - drug effects Sodium Chloride - pharmacology Vasoconstriction - drug effects Vasodilator Agents - pharmacology Yohimbine - pharmacology
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Summary:	The effects of adrenaline and noradrenaline on vascular postsynaptic alpha 1- and alpha 2-adrenoceptors were investigated in six healthy volunteers. The catecholamines were infused intra-arterially, in three cumulative doses, together with a continuous infusion of saline, doxazosin (alpha 1-selective antagonist), yohimbine (alpha 2-selective antagonist) or the combination of the two antagonists, and changes in forearm blood flow were measured by plethysmography. beta-adrenoceptor mediated effects of the catecholamines were prevented by concomitant intra-arterial infusion of propranolol. Adrenaline and noradrenaline reduced forearm blood flow dose-dependently and to the same extent. The vasoconstrictive effect of adrenaline and of noradrenaline was significantly reduced by doxazosin and by yohimbine, and, to a greater extent, by the combination of doxazosin and yohimbine. The magnitude of these reductions were approximately the same for adrenaline and noradrenaline. No changes in heart rate or blood pressure were observed during the infusions. It is concluded that exogenous adrenaline and noradrenaline produce vasoconstriction in the vasculature of the human forearm by stimulation of both postsynaptic alpha 1- and alpha 2-adrenoceptors.
ISSN:	0952-1178