Abstract

Estrogen and progesterone are ovarian steroid hormones involved in the initiation and maintenance of female sexual behaviors. Recent research suggests that testosterone (T) is also important in sexual behavior, particularly in the restoration of libido in surgically and naturally menopausal women when administered with estrogen (E). The effect of T on the female sexual behavior of aged intact, and young ovariectomized rats has been poorly described in the current literature, despite varying reports offacilitative and inhibitory effects. The goal of the present thesis was to examine the actions of E, T, or their combination, in the restoration of sexual activity at a time when ovarian function is altered either through aging or surgical removal of the ovaries. The effects of both acute and chronic administration of these hormones on sexual behavior were observed. The results of these experiments suggest that the combined action of E with T may facilitate sexual behaviors in young ovariectomized female rats, to levels equivalent to optimal priming with E and progesterone. When varying hormone regimens were administered to aged intact animals, by phasic subcutaneous injections every four days, there was no effect on their sexual behavior acutely, whereas chronic T and E+T resulted in an attenuation of sexual behaviors. When a continuous release of T was administered to aged intact female rat by subcutaneous capsule, sexual behaviors were initially facilitated, but the effect dissipated over time. The mechanism underlying this process is suggested.