title: The vasodilatory effects of ketamine on isolated rabbit portal veins.
abstract: The vasodilation mechanism induced by ketamine was investigated in isolated smooth muscle strips of rabbit portal veins. Ketamine inhibited both the phasic and tonic components of K(+)-induced contraction at concentrations greater than 500 microM and 100 microM, respectively. This effect was reversible and concentration-dependent with concentration-dependent with concentrations up to 1 mM. These effects were similar to those produced by verapamil. In the presence of 60 mM K+, application of Ca2+ (2.5 mM) in the perfusing solution caused tonic contraction of the smooth muscle, and ketamine at concentrations larger than 10 microM strongly inhibited this Ca(2+)-induced contraction. Ketamine (100 microM) also inhibited the K(+)-induced contractions significantly in the absence and presence of guanethidine, tetrodotoxin and propranolol. Ketamine produced similar concentration-dependent relaxations in the tissues with and without endothelium. These results indicate that in rabbit portal vein, vasodilation produced by ketamine is not endothelium-dependent but is likely to be due to blockade of the voltage-gated influx of extracellular Ca2+.
authors.affiliation: Department of Anaesthesiology, Faculty of Medicine, Toyama Medical and Pharmaceutical University, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Yamazaki
authors.forename: Y
authors.initials: Y
authors.lastname: Momose
authors.forename: K
authors.initials: K
authors.lastname: Shakunaga
authors.forename: K
authors.initials: K
authors.lastname: Kamitani
authors.forename: Y
authors.initials: Y
authors.lastname: Ito
mesh_terms: D000818:Animals; D002118:Calcium / Q000502:physiology*; D004347:Drug Interactions; D004730:Endothelium, Vascular / Q000502:physiology*; D066298:In Vitro Techniques; D007649:Ketamine / Q000494:pharmacology*; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D011169:Portal Vein / Q000187:drug effects; D011188:Potassium / Q000502:physiology; D011817:Rabbits; D013564:Sympathetic Nervous System / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects*
chemical_list: D007649:Ketamine; D011188:Potassium; D002118:Calcium