Responsiveness to estradiol in central nervous system of aging female rats.

The age related decline in reproductive capacity in the female rat is examined in terms of physiological and behavioral changes in responsiveness to estradiol evidenced during the second year of life. After 9-12 months of age, regular estrous cycles are replaced by constant estrous, prolonged pseudopregnancy, or anestrous states, with concurrent alterations in endocrine function. Some of the mechanisms implicated in the mediation of these changes are reviewed. Estrogenic influences on estrous behavior and the control of feeding and body weight in aged rats, as well as the effects of parity on aged endocrinological functioning are discussed.