Comparing the relaxing effects of desflurane and sevoflurane on oxytocin-induced contractions of isolated myometrium in both pregnant and nonpregnant rats

In this study, the effects of 2 volatile anesthetics, desflurane and sevoflurane, on oxytocin-induced contractions of isolated myometrium in pregnant and nonpregnant rats were compared. Twenty pregnant and 20 nonpregnant Wistar albino rats were studied at 19 to 20 days' gestation (term, 22 days). A total of 40 myometrial strips were obtained from pregnant and nonpregnant rats, and each of these was randomly assigned to 1 of 4 groups (n=10, each group). After spontaneous myometrial contractions were induced in the De Jalon solution, the effects of 0.5, 1, and 2 minimum alveolar anesthetic concentrations (MAC) of desflurane or sevoflurane, in the absence and presence of oxytocin (2 x 10(-9) M), were investigated. Oxytocin significantly increased the amplitude and duration of spontaneous contractions in longitudinal myometrial strips (P < .05), but not the frequency. Both agents (except for 0.5 MAC in the nonpregnant group) inhibited the duration, amplitude, and frequency of induced contractions in a dose-dependent manner. The inhibitory potencies of desflurane and sevoflurane were similar. It was found that isolated strips of pregnant rat myometrium were more sensitive to the inhibitory effects of both agents than were the nonpregnant rat myometrial strips.