THE EFFECTS OF VALATILE ANESTHETICS ON VASCULAR SMOOTH MUSCLE

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This study was designed to investigate the effects of volatile anesthetics on isolated canine mesenteric artery and vein. Method ; The experiments were performed on isolated mesenteric arteries and veins from mongrel dogs (7-20kg) anesthetized with sodium pentobarbital (25mg/kg, IV.). After the perivascular fat and connective tissue were dissected away, artery and vein were cut into rings which were suspended into organ bath chamber filled with Krebs-Ringer solution (20ml) for isometric tension measurements. Effects of halothane, isoflurane and sevoflurane on tension development induced by norepinephrine (NE,10^<-8>-10^<-3>M), tyramine (Tyr, 10^<-8>-10^<-3>M) and electrical field stimulation (ES ; 9V,2ms, 1-32Hz) were investigated. Volatile anesthetics were delivered from a vaporizer into the O_2 -CO_2 mixture aerating bathing media. The concentration in the resulting gas mixture was monitored continuously by an anesthetic gas analyzer. Results ; In concentration (1,2MAC) used, halothane, isoflurane and sevoflurane did not effect basal tension of blood vessel rings. However, halothane, isoflurane and sevoflurane attenuated ES induced maximum contraction of vein rings by same extend. Halothane, isoflurane and sevoflurane did not inhibited Tyr induced contraction in both artery and vein. Halothane and isoflurane but not sevoflurane, attenuated maximum contraction by NE in mesenteric vein. Conclution ; These results suggested that (1) halothane, isoflurane and sevoflurane may inhibit Ca^<2+>-dependent NE release from sympathetic nerve endings of mesenteric vein. (2) halothane and isoflurane inhibit alpha-adrenoceptor mediated vascular smooth muscle contraction of mesenteric vein.