The mechanism of direct relaxant effects of propofol on rabbit tracheal smooth muscle / 中华麻醉学杂志

ABSTRACT

Objective To investigate the possible mechanism of direct relaxant effects of propofol on tracheal smooth muscle.Methods Nine Japanese long-ear white rabbits of either sex, weighing 2-3 kg were sacrificed by air embolism. The trachea of each rabbit was removed and cut into six strips of (6-8) mm x (12-15) mm. The tracheal strips were suspended in Kreb' s solution, exposed to 95 % O2 and 5 % CO2 mixture and maintained at 37℃. One end of strip was fixed and the other was connected to a tension monitor through a tension transducer. The experiment was divided into six groups group I propofol; group Ⅱ propofol + indothelin; group Ⅲp Ⅴ propofol + verapamil and group Ⅵ propofol + glibenclamide. In each group the tracheal strips were precontracted with acetylcholine (10-5 mol? L-1). The strips were then exposed to increasing concentrations of propofol (5 ? 10-3 , 10-2 ,2.5 ? 10-2 , 5 ? 10-2 , 10-1 mg?ml-1 ). At each concentration of propofol, the change in muscle tension was allowed to reach the steady state for 30 min. In group I no other drug was added to the Kreb' s solution besides propofol, while in group Ⅱ-Ⅵ before the effects of propofol were determined, the strips were pretreated with indothelin (10-4 mol? ml-1 ) (in group Ⅱ), L-NAME(10-4 mol?ml-1) (in group Ⅲ), methylene blue (10-5 mol?ml-1) (in group Ⅳ), verapamil (10-5 mol?ml-1) (in group Ⅴ) or glibenclamide (10-5 mol?ml-1) (in group Ⅵ). Results The three concentrations of propofol examined (2.5?10-2, 5?10-2 and 10-1 mg?ml-1) produced relaxation of isolated tracheal smooth muscle. In group Ⅱ , Ⅲ , Ⅳand Ⅴ pretreatment of tracheal strips with indothelin, L-NAME, methylene blue or verapamil did not significantly affect the relaxation of tracheal smooth muscle induced by propofol as compared with group Ⅰ. Pretreatment with glibenclamide significantly depressed the direct relaxant effect of propofol on tracheal smooth muscle ( P