Journal of North Khorasan

Abstract Background and Objective: The present study was carried out to evaluate the antinociceptive effect of morphine in ovariectomized female rats in comparison with naïve and estradiole-treated ovariectomized rats. Matial and Methods: 30 female rats were divided into 3 groups: 1) Sham (control group) 2) OVX (ovarictomized) 3) OVX Est. (ovarictomized and estradiole treated). Estradiol valerate (2mg/kg/week, i.m.) was injected in the animals of OVX Est. The animals of Sham and OVX groups received 2ml/kg/week saline instead of estradiole. The hot plate test was carried out as a base record 15 min before injection of morphine (10 mg/kg S.C.) and consequently it was repeated 5 times, every15 minutes after injection. The results were compared using one way and repeated-measure analysis of variance (ANOVA) followed by post-hoc Tukey’s test. Differences were considered statistically significant when P <0.05. Results: The reaction times after injection of morphine in sham and OVX Est groups were significantly higher than basal reaction time (P <0.05 and P <0.001) but in OVX group there were no significant differences. However, the reaction times after injection of morphine in OVX, OVX Est and sham groups were not significantly different. Conclusion: It is concluded that ovarian hormones change analgesic effects of morphine in rats.