Effects of droperidol on cardiovascular adrenoceptors.
The influence of droperidol on the pressor effect of noradrenaline was investigated in pithed rats injected with propranolol. Droperidol induced a dose-dependent shift of the noradrenaline dose-response curve to the right, but proved to be 20 times less potent than phentolamine. Droperidol produced a considerably more pronounced inhibition of the effect of tyramine than of that of noradrenaline.--The influence of droperidol on the increase in tension induced by noradrenaline was determined in isolated aortic strips of rats. The drug caused a marked parallel shift of the noradrenaline concentration-response curve to the right (pA2:7.99). In this preparation droperidol and phentolamine were equieffective.--Droperidol did not produce a significant shift of the noradrenaline concentration-response curves obtained for the positive chronotropic and inotropic effects in spontaneously beating right guinea-pig atria and in electrically driven left atria, respectively.--It is concluded that droperidol is a competitive inhibitor of the vascular alpha-adrenoceptors, leaving the beta-adrenoceptors of the heart unaffected, and that it inhibits the neuronal uptake mechanism of noradrenaline.
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D001808:Blood Vessels / Q000187:drug effects* / Q000294:innervation; D004305:Dose-Response Relationship, Drug; D004329:Droperidol / Q000494:pharmacology*; D004347:Drug Interactions; D006168:Guinea Pigs; D006321:Heart / Q000187:drug effects* / Q000294:innervation; D006339:Heart Rate / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D009638:Norepinephrine / Q000494:pharmacology; D010646:Phentolamine / Q000494:pharmacology; D051381:Rats; D011941:Receptors, Adrenergic / Q000187:drug effects*; D013997:Time Factors; D014439:Tyramine / Q000494:pharmacology
D011941:Receptors, Adrenergic; D004329:Droperidol; D009638:Norepinephrine; D014439:Tyramine; D010646:Phentolamine