Aim: The aim of this study was to investigate the effects of melatonin on spontaneous and oxytocin-induced contractility of myometrim isolated from pregnant women.

Material and Methods: Myometrial strips were removed from pregnant women undergoing elective sezarien section and placed in an organ bath containing Lehrer solution at 37°C and pH 7.4, constantly bubbled with 95% oxygen-5% carbon dioxide and isometric contractions were recorded. Effects of cumulative concentrations of melatonin (1-25µ M) on amplitude and frequency of spontaneous and oxytocin-induced contractions were studied. Statistical analysis was performed using Kruskal Wallis analysis of variance.

Results: Melatonin inhibited amplitude and frequency of both spontaneous and oxytocin-induced contractions of myometrium in a dose-dependent manner.

Conclusions: Data from this study indicate that melatonin inhibits spontaneous and oxytocin-induced contractions in of myometrium isolated pregnant woman.