The comparison of the relaxant effects of propofol, thiopental, ketamine, and etomidate on isolated rat uterine smooth muscle / 대한마취과학회지

BACKGROUND: Intravenous hypnotics are used in pregnancy, labor and delivery. The aim of the present study was to investigate and compare the relaxant effects of propofol, thiopental, ketamine, and etomidate on isolated rat uterine smooth muscles. METHODS: Uterine smooth muscle preparations were obtained from non-pregnant female rats. The uterus of the rat was dissected and cut into 10 mm strips. The muscle strips were bathed in Krebs solution. After spontaneous uterine contractile activity had been accomplished, propofol, ketamine, thiopental, and etomidate in various concentrations were added cumulatively to the baths and resting tension, active tension, and frequency of contration were recorded at each concentration of agents. EC(5), EC(25), EC(50), EC(75), and EC(95) of each drug on active tension and frequency of contraction were calculated using a probit model. RESULTS: Propofol, thiopental, and etomidate reduced uterine contractions in a concentration-dependent manner. Ketamine concentrations of 10(-7) to 10(-5) M augmented uterine contractions but ketamine concentrations of 10(-4) to 10(-3) M attenuated uterine contractions. The EC(50)'s of propofol, thiopental, ketamine, and etomidate on active tension were 1.56 x 10(-5) M, 4.97 x 10(-5) M, 3.52 x 10(-4) M, and 2.73 x 10(-5) M, respectively. CONCLUSIONS: All four intravenous hypnotics relaxed the uterine smooth muscle of rats except for ketamine in low concentrations (10(-7) to 10(-5) M). Propofol had the greatest relaxant effects on isolated rat uterine smooth muscle among these hypnotics. It seems that ketamine is a suitable obstetric hypnotic agent for hypovolemic parturients and propofol is a useful hypnotic agent for uterine relaxation during pregnancy.

The Effects of Propofol on the Contraction in the Rat Uterine Smooth Muscle / 대한마취과학회지

BACKGROUND: Propofol is an alternative to thiopental as an intravenous induction agent for cesarean section. It is also used as a sedative for supplementation of regional blockade during cesarean section. It has been reported that propofol relaxes not only vascular smooth muscle but also other smooth muscles. The aim of this study was to investigate the effect of propofol on rat uterine smooth muscle in an isolated preparation in the rat. METHODS: Uterine smooth muscle tissues were obtained from rats (n = 21). The muscle strips were suspended in tissue baths and isometric tension was recorded. After spontaneous or oxytocin induced activity had been accomplished in the buffer solution as a control, propofol (1 to 20microgram/ml) in fat emulsion was applied cumulatively to the bath and the effects were continuously recorded. RESULTS: In vitro, propofol induced a dose-dependent inhibition of spontaneous as well as oxytocin induced myometrial contractile activity. Propofol concentration of 1microgram/ml had no significant effects on the resting tension, active tention, and frequency of contraction developed by spontaneous and oxytocin induced uterine contractility. However, Complete muscular relaxations on spontaneous and oxytocin induced contractility were obtained at a concentration of 10microgram/ml and 20microgram/ml, respectively. CONCLUSIONS: Propofol inhibits spontaneous and oxytocin-induced uterine smooth muscle contractions in dose dependent pattern.

The Effects of Nitroglycerin on the Contraction of Rat Uterine Smooth Muscle / 대한마취과학회지

BACKGROUND: It has been reported that nitroglycerin relaxes not only vascular smooth muscle but also uterine smooth muscle. The aim of the present study was to investigate the effect of nitroglycerin on rat uterine contractile activity in vitro. The effects of nitroglycerin on myometrial spontaneous activity and oxytocin-induced contractions were also observed. METHODS: Uterine smooth muscle tissues were obtained from non-pregnant female rats (n = 21). The uterine segments were mounted in tissue baths. After spontaneous or oxytocin-induced activity had been accomplished, nitroglycerin in various concentrations was added to the bath and the effects were continuously registered. RESULTS: Nitroglycerin induced a dose-dependent inhibition of spontaneous as well as oxytocin-induced myometrial contractile activity. Complete muscular relaxation on spontaneous contractility was obtained at a concentration of 50 microgram/ml. Complete muscular relaxation on oxytocin-induced contractility was obtained at a concentration of 75 microgram/ml. CONCLUSIONS: Nitroglycerin inhibited the uterine contractile response to exogenous oxytocin as well as spontaneous in the estrous rat.