title: Propofol-induced depression of cultured rat ventricular myocytes is related to the M2-acetylcholine receptor-NO-cGMP signaling pathway.
abstract: BACKGROUND
  It is well-known that propofol sometimes causes bradycardia or asystole during anesthesia; however, the direct effect of propofol on the myocardium remains unclear. Previous reports showed the contribution of muscarinic acetylcholine receptors to propofol-induced bradycardia. Conversely, it was suggested recently that nitric oxide (NO) plays an important role in mediating the effect of vagal stimulation in the autonomic regulation of the heart. Therefore, the authors investigated the effects of propofol on spontaneous contraction and NO production in cultured rat ventricular myocytes.
  
  
  METHODS
  The authors measured chronotropic responses of cultured rat ventricular myocytes induced by propofol stimulation with a sensor, a fiber-optic displacement measurement instrument. The authors also quantitatively analyzed NO metabolite production in cultured myocytes by measuring the levels of nitrite and nitrate in a high-performance liquid chromatography reaction system. The influence of propofol on muscarinic acetylcholine receptors of myocyte membranes was also measured with a competitive binding assay using [3H]quinuclidinyl benzilate ([3H]QNB).
  
  
  RESULTS
  Propofol caused negative chronotropy in a dose-dependent manner. Propofol (IC50) also caused the enhancement of nitrite production in cultured myocytes. Eighty percent of the enhancement of nitrite production induced by propofol (IC50) stimulation was abolished by pretreatment with atropine, methoctramine, or N(G)-monomethyl-L-arginine acetate (L-NMMA). The negative chronotropy induced by propofol (IC50) stimulation was reduced to 40-50% by pretreatment with atropine, methoctramine, L-NMMA, or 1H[1,2,4]oxadiazolo[4,3-alpha]quanoxalin-1-one, a selective inhibitor of guanylyl cyclase. Propofol displaced [3H]QNB binding to the cell membrane of myocytes in a concentration-dependent manner.
  
  
  CONCLUSIONS
  These results suggest that the negative chronotropy induced by propofol is mediated in part by M2-acetylcholine receptor activation, which involves the enhancement of NO production in cultured rat ventricular myocytes.
authors.affiliation: Department of Anesthesiology, Sapporo Medical University School of Medicine, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Yamamoto
authors.forename: S
authors.initials: S
authors.lastname: Kawana
authors.forename: A
authors.initials: A
authors.lastname: Miyamoto
authors.forename: H
authors.initials: H
authors.lastname: Ohshika
authors.forename: A
authors.initials: A
authors.lastname: Namiki
mesh_terms: D018686:Anesthetics, Intravenous / Q000494:pharmacology*; D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000502:physiology*; D003864:Depression, Chemical; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006321:Heart / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects; D006352:Heart Ventricles / Q000187:drug effects / Q000378:metabolism; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D009569:Nitric Oxide / Q000096:biosynthesis / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D015742:Propofol / Q000494:pharmacology*; D011869:Radioligand Assay; D051381:Rats; D017208:Rats, Wistar; D043585:Receptor, Muscarinic M2; D011976:Receptors, Muscarinic / Q000187:drug effects* / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects*; D019323:omega-N-Methylarginine / Q000494:pharmacology
chemical_list: D018686:Anesthetics, Intravenous; D004791:Enzyme Inhibitors; D043585:Receptor, Muscarinic M2; D011976:Receptors, Muscarinic; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D006152:Cyclic GMP; D015742:Propofol