title: Investigation of the relaxant effects of pancuronium, rocuronium, vecuronium and mivacurium on rat thoracic aorta.
abstract: OBJECTIVE
  Pancuronium, vecuronium, mivacurium and rocuronium are nondepolarizing neuromuscular blocking agents, which are competitive antagonists against acetylcholine at nicotinic receptors, and considered to have no direct actions on vascular smooth muscle. We aimed to investigate the relaxant effects and possible underlying mechanisms of these agents on isolated rat thoracic aorta.
  
  
  METHODS
  The preparations were precontracted with prostaglandin F2alpha (10(-7) mol l(-1)) and pancuronium (10(-7)-10(-4) mol l(-1)), rocuronium (10(-7)-10(-4) mol l(-1)), vecuronium (10(-7)-10(-4) mol l(-1)) and mivacurium (10(-7)-10(-4) mol l(-1)) added at cumulative concentrations in the presence or absence of a prostaglandin synthesis inhibitor, indomethacin (10(-6) M), and a nitric oxide synthesis inhibitor, N(omega)-nitro-L-arginine methylester (3 x 10(-5)). The same protocol was applied to both endothelia (+) and endothelia (-) aortic rings. The preparations precontracted with prostaglandin F2alpha (10(-7) mol l(-1)) were stimulated with electrical field stimulation at a frequency of 10 Hz as square-wave pulses of 50 V (0.2 ms) in the presence of a noradrenaline reuptake inhibitor desipramine (10(-7) mol l(-1)) and a nonselective beta-blocker propranolol (10(-6) mol l(-1)). Drugs were added at ineffective concentration of 10(-7) mol l(-1). Tetrodotoxin (10(-7) mol l(-1)) was added to test whether the changes were dependent on the neuronal response.
  
  
  RESULTS
  Pancuronium and rocuronium relaxed aortic rings precontracted by prostaglandin F2alpha in a dose-dependent manner, but vecuronium and mivacurium did not. The relaxation effect of pancuronium and rocuronium was endothelium independent because there was not a significant response difference from the endothelium-denuded group.
  
  
  CONCLUSIONS
  In conclusion, their relaxation effect may be due to an increase in prostaglandin synthesis. The increased relaxation effect of these agents at electrical field stimulation may be by the decreasing effect of noradrenaline reuptake from nerve endings because a noradrenaline reuptake inhibitor desipramine did not change this effect. Also, these neuromuscular agents may affect beta-receptors, because a nonselective beta-blocker agent, propranolol, decreased their electrical field stimulation-induced relaxations.
authors.affiliation: Department of Anaesthesiology, Cumhuriyet University School of Medicine, Sivas, Turkey. gungursoy@gmail.com
authors.forename: Sinan
authors.initials: S
authors.lastname: Gursoy
authors.forename: Ihsan
authors.initials: I
authors.lastname: Bagcivan
authors.forename: Nedim
authors.initials: N
authors.lastname: Durmus
authors.forename: Kenan
authors.initials: K
authors.lastname: Kaygusuz
authors.forename: Iclal Ozdemir
authors.initials: IO
authors.lastname: Kol
authors.forename: Sahin
authors.initials: S
authors.lastname: Yildirim
authors.forename: Caner
authors.initials: C
authors.lastname: Mimaroglu
mesh_terms: D000732:Androstanols / Q000494:pharmacology*; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects*; D007546:Isoquinolines / Q000494:pharmacology*; D008297:Male; D000077590:Mivacurium; D010197:Pancuronium / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D000077123:Rocuronium; D014673:Vecuronium Bromide / Q000494:pharmacology*
chemical_list: D000732:Androstanols; D007546:Isoquinolines; D000077590:Mivacurium; D014673:Vecuronium Bromide; D010197:Pancuronium; D000077123:Rocuronium