Effect of Repeated Immobilization Stress on Ovarian Function in Female Rats

Objective To observe the effects of repeated immobilization on rats ovarian function and to observe the changes of ovarian function in menopause animals.Methods Daily vaginal smears were permfored to follow the estrous cycle in adult female rats.The animals with regular cycle were exposed to the scheduled daily repeated immobilization for 15-day,which included 5 stress episodes with each episode consisting of three immobilizations (one time per day). The duration of immobilization was progressively increased with the subsequent episode. Serum levels of estradiol (E2) and progesterone (P) were measured throughout the estrous cycle before and after the stress.Results The repeated stress resulted in the disruption of the estrous cycle characterized by longer phase of diestrus or by fewer epithelium from vagina in proestrus and estrus.In the stressed rats, a significant decrease of serum E2 and an increase of P were shown throughout the cycle compared to that before stress;the normal secretion cycle was interrupted or even disappeared; changes of serum P level in some rats were similar to the menopause animals.Conclusion Repeated immobilization can cause the disruption or degeneration of ovarian function,indicating that rats with stress-induced ovarian dysfunction is an appropriate animal model for testing protective effects of agents against aging and for the diseases related to ovarian dysfunction.