Leila Roshangar - Department of Embryology and Histology, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran.
Jafar Soleimani Rad - Department of Embryology and Histology, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran.
Parisa Nikpoo - Drug Applied Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
Manijeh Sayyah Melli - Gynecologist, Tabriz University of Medical Sciences, Alzahra Hospital, Tabriz, Iran.

Background: Induction of ovulation in ART is necessary for superovulation and the side effects of superovulatory drugs are debated. Oxytocin as a natural hormone, havereceptors and is synthesized by several reproductive organs. Preovulatory presence of oxytocin receptor mRNAs in granulosa cells indicating a role for oxytocin in folliculardevelopment. Objective: The aim of the present study was to investigate the effect of exogenousoxytocin injection on folliculogenesis, ovulation and endometrial growth in mice. Materials and Methods: Forty adult female mice were divided into two groups ascontrol and experimental. The mice at their sterous cycle received 1 IU/gr oxytocin, in experimental, and the same volume of solvent in control groups. Half of the mice ineach group are sacrificed at 24 hours post injection and the other half, 48 hours after the injection. Ovarian samples fixed in 10% formalin, embedded in paraffin and sections were stained with H and E and studied using stereological techniques. The data wereanalyzed with Man – Whitney test. Results: Microscopic examination revealed that the number and morphological featuresof follicles at different stages were similar at 24 and 48 hours post injection in both groups. The volumes of the ovaries were similar in both groups at 24 hour. However, at48 hour, the volume of ovaries, corpora lutea and endometrial thickness, in experimental group, were significantly higher than those in control group (p< 0.05). Conclusion: According to the increased volume of corpus luteum in the experimental group, it is concluded that oxytocin injection has a stimulatory effect on induction of ovulation.

Oxytocin, Folliculogenesis, Ovulation, Endometrium, Mouse