Abstract: In experimental group of female SD rats at the age of 11-15 months and control group of those at 3-5 months, the serum levels of gonadotropin and sex hormones were detected, smear of vaginal cell, structure of ovary, uterus and adrenal cortex, changes of atrial specific granule （ASG） were observed by microscope and electron microscope. The results showed no regular estrous cycle in experimental rats, the levels of serum estradiol （E₂） reduced and LH elevated significantly, FSH rose slightly, there is reduction in the number of the primordial, primary and secondary oogoniums with increase in degenerated oogoniums. The histological changes in the ovary and endometrium were not matched with each other,the myocardium showes the tendency of senile changes. The results suggest that the female SD ras at the age of 11-15 months enter their natural climacteric and perhaps it can be adopted as the animal model for human climacterie study.

Key words: Climacteric, Rat, Sex hormone, Estrous cycle