This study was designed to determine the effect of nebivolol, which is a selective β1 blocker and has nitric oxide (NO) mediated effects, on oxytocin induced isolated myometrial contractions.

Ten adult Wistar female rats, weighting between 250-300 grams, were used in our study. Oestrus cycles were determined by taking vaginal smears everyday. The day when sperm was determined on smear was accepted as the first day of pregnancy. On 16th day of pregnancy, rats were killed by cervical dislocation. Placentas and fetal tissues were seperated from each uterus and placed in Krebs solutions. Myometrium strips measuring 1x 0,2x 0,2 cm. were prepared and placed in an organ bath containing krebs solution constantly bubbled with 95% oxygen, 5% carbon dioxide, at 37 ºC and pH 7,4. Under 1 gram of resting tension, isometric contractions were recorded. Spontaneous contractions were seen for 30 minutes and then myometrial activity was stimulated with oxytocin. After stimulation with oxytocin different doses of nebivolol (50,250 and 500 µM) were applied.

Addition of 50, 250 and 500 µM nebivolol showed statistically significant decrease on mean peak amplitude, mean frequency and mean area under curve (p<0,05 Wilcoxon Rank Test). But no statistically significant difference was determined on mean peak amplitude after addition of 50 µM nebivolol.

It was determined that nebivolol, a beta blocker, had an inhibitory effect on oxytocin-induced contractions of myometrium.