Oestradiol and progesterone treatment and precopulatory behaviour in female rats ovariectomized at different ages.

The dependence of patterning of sexual behaviour was ascertained in female rats ovariectomized prepubertally as well as postpubertally on the oestradiol and progesterone treatment. As the criterion of sexual behaviour both the copulatory and precopulatory patterns were used. The hormonal treatment starting from the 5th day following ovariectomy was repeated at weekly intervals for several weeks. The females ovariectomized on the 23rd and 30th day exhibited less complete sexual patterns in comparison with the females sprayed on the 70th and the 145th day. The majority of the oldest animals exhibited, in fact, a complete sexual pattern. Incomplete sexual patterns induced in the females ovariectomized on the 30th day, but treated from the 75th day onwards suggest that exogenous ovarian hormones could not compensate for the effectiveness of endogenous hormones. The omission of hormonal treatment resulted in the rapid fall of sexual behaviour in females ovariectomized during adulthood. However, in the females ovariectomized on the 30th day a gradual decrease of sexual behaviour was found. The findings suggest that the development of sexual behavioural repertoire in female rats is not terminated at puberty, but that it proceeds together with the increasing number of oestrous cycles.