[Effect of halothane on the mechanical properties of rabbit right ventricular papillary muscle in the presence of either alpha or beta stimulant positive inotropic agent].
The effects of halothane (1-3 MAC) on the isometric twitch tension, the contracture tension induced by 1 mM barium (Ba2+) in the rabbit right ventricular papillary muscles, and the transient tension response to step length change during barium contracture, were analyzed in the presence of either alpha (3 x 10(-5) M phenylephrine+10(-6) M bupranolol) or beta (10(-7) M isoproterenol) stimulants. The isometric twitch tension was significantly decreased with the administration of halothane dose dependently, in the presence of both alpha or beta stimulants. Both the time to peak (TP) and the time to half relaxation (THR) were remarkably shortened with the administration of halothane in the presence of both alpha or beta stimulants. The Ba2+ contracture tension was also decreased with the administration of halothane dose dependently in the presence of both alpha or beta stimulants. The tension transient became faster with the administration of halothane in the presence of the alpha stimulant, but not in the presence of the beta stimulant. These results suggest that halothane decreases the number of active crossbridges regardless of the inotropic states induced by the two different stimulants. Also on increase the rate of crossbridge kinetics occurs in the presence of the alpha stimulant but not in response to the beta stimulant.
Koike
H
H
Department of Dental Anesthesiology, Tsurumi University School of Dental Medicine, Yokohama.
D000818:Animals; D002046:Bupranolol / Q000494:pharmacology*; D006221:Halothane / Q000494:pharmacology*; D007545:Isoproterenol / Q000494:pharmacology*; D009132:Muscles / Q000187:drug effects* / Q000502:physiology; D010656:Phenylephrine / Q000494:pharmacology*; D011817:Rabbits
D010656:Phenylephrine; D002046:Bupranolol; D007545:Isoproterenol; D006221:Halothane