title: Effects of fentanyl on the rat aorta are mediated by alpha-adrenoceptors rather than by the endothelium.
abstract: 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.
authors.affiliation: Department of Medicine, University of Melbourne, Royal Melbourne Hospital, Parkville, Victoria, Australia.
authors.forename: F
authors.initials: F
authors.lastname: Karasawa
authors.forename: V
authors.initials: V
authors.lastname: Iwanov
authors.forename: R F
authors.initials: RF
authors.lastname: Moulds
mesh_terms: 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
chemical_list: D011942:Receptors, Adrenergic, alpha; D010656:Phenylephrine; D009270:Naloxone; D005283:Fentanyl