Effects of fentanyl on the rat aorta are mediated by alpha-adrenoceptors rather than by the endothelium.
We have assessed if fentanyl interacts with the endothelium to affect vessel tone. In the presence or absence of endothelium, fentanyl in concentrations greater than 10(-7) mol litre-1 decreased the sensitivity of the rat aortic rings to phenylephrine, but fentanyl in smaller concentrations had no significant effect. Rings, with or without endothelium, and pre-contracted by phenylephrine were relaxed by fentanyl, and this relaxation was not inhibited by the opioid receptor antagonist, naloxone. Pretreatment of the rings with either fentanyl or phentolamine protected alpha-adrenoceptors from block by the alpha-adrenoceptor antagonist, phenoxybenzamine. We conclude that, in the rat aorta, fentanyl-induced relaxation was mediated by alpha-adrenergic receptors, and that the endothelium modulated, but did not mediate, this relaxation.
Karasawa
F
F
Department of Medicine, University of Melbourne, Royal Melbourne Hospital, Parkville, Victoria, Australia.
Iwanov
V
V
Moulds
R F
RF
D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects* / Q000502:physiology; D046508:Culture Techniques; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000502:physiology; D005260:Female; D005283:Fentanyl / Q000494:pharmacology*; D008297:Male; D009270:Naloxone / Q000494:pharmacology; D010656:Phenylephrine / Q000037:antagonists & inhibitors; D051381:Rats; D017207:Rats, Sprague-Dawley; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D014664:Vasodilation / Q000187:drug effects* / Q000502:physiology
D011942:Receptors, Adrenergic, alpha; D010656:Phenylephrine; D009270:Naloxone; D005283:Fentanyl