Oxytocin can affect follicular development in the adult mouse.

Injection of oxytocin into normal adult cycling mice caused alterations in ovarian histology. Oxytocin was administered early on the day of pro-oestrus and it induced the appearance of large numbers of corpora lutea by late pro-oestrus, suggesting oxytocin stimulated ovulation. When mice were examined very early on the day of normal oestrus the ovarian population of follicles was different in the experimental group from that in the control mice, there being increased numbers of preantral and antral follicles in treated animals. As oxytocin can cause an alteration in the timing of follicular maturation and ovulation processes study of communications between the adenohypophysis and areas containing oxytocin might be important for understanding physiological details of ovulation. The relative times at which, for instance, antral follicle and corpora lutea populations increased suggested that oxytocin might have more than one activity which affects ovarian behaviour.