title: Remifentanil produces vasorelaxation in isolated rat thoracic aorta strips.
abstract: BACKGROUND
  Remifentanil can cause transient instability in hemodynamic variables. However this change may not be solely the result of autonomic or central nervous system inhibition or of centrally mediated vagal stimulation. In this study, the aim was to examine the direct effects of remifentanil on isolated thoracic aorta strips in vitro.
  
  
  METHODS
  Forty-five Wistar rat thoracic aorta rings were isolated, and contraction-relaxation responses were recorded.
  
  
  RESULTS
  In aortic rings precontracted with phenylephrine or potassium chloride, remifentanil produced concentration-dependent relaxation in both endothelium-intact and denuded rings (P<0.001). Remifentanil induced significantly greater relaxation in intact rings than in those denuded of endothelium, regardless of whether they were precontracted with phenylephrine hydrochloride or KCl (P<0.001). When the endothelium was present, remifentanil produced greater relaxation in KCl-contracted rings than in PE-contracted rings at lower concentrations (10-9 and 10-8), and similar relaxation at higher concentrations (10-7 and 10-6). However, when the endothelium was removed, relaxation was similar in both solutions, at all concentrations (10-9 to 10-6). In intact rings, pretreatment with L-NO-ARG or indomethacin reduced the degree of remifentanil-induced relaxation. In Ca+ +/- free media, calcium-dependent KCl contractions were inhibited in a dose-dependent manner by remifentanil (P<0.001).
  
  
  CONCLUSIONS
  Remifentanil vasodilates by an endothelium-dependent mechanism, involving prostacyclin and nitric oxide released from the endothelium. Its endothelium-independent vasodilation probably occurs via the suppression of voltage-sensitive Ca++ channels.
authors.affiliation: Department of Anesthesiology, Cukurova University, Faculty of Medicine, Adana, Turkey. unlugenc@mail.cu.edu.tr
authors.forename: H
authors.initials: H
authors.lastname: Unlügenç
authors.forename: M
authors.initials: M
authors.lastname: Itegin
authors.forename: I
authors.initials: I
authors.lastname: Ocal
authors.forename: M
authors.initials: M
authors.lastname: Ozalevli
authors.forename: T
authors.initials: T
authors.lastname: Güler
authors.forename: G
authors.initials: G
authors.lastname: Isik
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects; D011464:Epoprostenol / Q000502:physiology; D066298:In Vitro Techniques; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009569:Nitric Oxide / Q000502:physiology; D010656:Phenylephrine / Q000037:antagonists & inhibitors / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology*; D011189:Potassium Chloride / Q000037:antagonists & inhibitors / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D000077208:Remifentanil; D014662:Vasoconstrictor Agents / Q000037:antagonists & inhibitors / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects*
chemical_list: D000701:Analgesics, Opioid; D002121:Calcium Channel Blockers; D010880:Piperidines; D014662:Vasoconstrictor Agents; D010656:Phenylephrine; D009569:Nitric Oxide; D011189:Potassium Chloride; D011464:Epoprostenol; D000109:Acetylcholine; D000077208:Remifentanil