title: Investigation of the vasorelaxant effects of moxonidine and its relaxation mechanism on the human radial artery when used as a coronary bypass graft.
abstract: OBJECTIVE
  In both low- and high-risk patients undergoing coronary artery bypass grafting, the internal mammary artery is the first choice of arterial graft, and the second choice is the radial artery (RA). Unfortunately, RA spasms are a significant problem for a surgical team to overcome in the perioperative and postoperative period. In current surgical practice, the use of vasodilator agents perioperatively in the pending graft preparation is generally accepted and these may be implemented topically, endoluminally or both ways. Moxonidine is the latest second-generation, centrally acting antihypertensive agent, and the intention in this paper is to investigate its direct vasorelaxant effects and relaxation mechanisms on the human radial artery in vitro.
  
  
  METHODS
  RA rings were mounted in an organ bath and tested for changes in isometric tension in its relaxation response to moxonidine in the presence and absence of NG-nitro-L-arginine methyl ester (L-NAME, non-specific inhibitor of nitric oxide synthase), idazoxan (non-selective I1 and α2-antagonist) and yohimbine (selective α2-antagonist).
  
  
  RESULTS
  Moxonidine induced concentration-dependent relaxations on the RA rings precontracted with phenylephrine (P < 0.05). L-NAME and idazoxan significantly reduced the relaxation caused by moxonidine (P < 0.05), while yohimbine significantly increased the relaxation by moxonidine (P < 0.05). In the presence of L-NAME + idazoxan, the relaxation by moxonidine was eliminated completely (P < 0.05).
  
  
  CONCLUSIONS
  We speculate that the relaxant effect of moxonidine may be attributed partly to the synthesis and/or release of nitric oxide, and partly to the stimulation of imidazoline I1 receptors. We suggest that moxonidine may help to prevent RA spasms during the preparation period in operation when used topically or/and endoluminally.
authors.affiliation: Department of Pharmacology, Cumhuriyet University, Sivas, Turkey.
authors.forename: Bulent
authors.initials: B
authors.lastname: Sarac
authors.affiliation: Department of Cardiovascular Surgery, Cumhuriyet University, Sivas, Turkey ozgekorkmaz73@hotmail.com.
authors.forename: Ozge
authors.initials: O
authors.lastname: Korkmaz
authors.affiliation: Department of Pharmacology, Cumhuriyet University, Sivas, Turkey.
authors.forename: Ahmet
authors.initials: A
authors.lastname: Altun
authors.affiliation: Department of Pharmacology, Cumhuriyet University, Sivas, Turkey.
authors.forename: Ihsan
authors.initials: I
authors.lastname: Bagcivan
authors.affiliation: Department of Cardiovascular Surgery, Cumhuriyet University, Sivas, Turkey.
authors.forename: Sabahattin
authors.initials: S
authors.lastname: Göksel
authors.affiliation: Department of Pharmacology, Cumhuriyet University, Sivas, Turkey.
authors.forename: Sahin
authors.initials: S
authors.lastname: Yildirim
authors.affiliation: Department of Cardiovascular Surgery, Cumhuriyet University, Sivas, Turkey.
authors.forename: Ocal
authors.initials: O
authors.lastname: Berkan
mesh_terms: D000959:Antihypertensive Agents / Q000494:pharmacology; D001026:Coronary Artery Bypass / Q000379:methods*; D003324:Coronary Artery Disease / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery*; D005260:Female; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D017534:Radial Artery / Q000187:drug effects / Q000637:transplantation*; D014664:Vasodilation / Q000187:drug effects*
chemical_list: D000959:Antihypertensive Agents; D007093:Imidazoles; C043482:moxonidine
keywords: Coronary artery bypass graft; Human radial artery; Moxonidine; Relaxation