Estradiol plus progesterone treatment and precopulatory behavior in prepubertally ovariectomized female rats: dose-response relationships.

The copulatory and precopulatory behavioral repertoire expressed in terms of the intensity scale of sexual responsiveness was investigated in female rats ovariectomized on the 30th day after birth and treated for 9 weeks, once weekly, with estradiol dipropionate (5, 10, 15, 20, and 30 micrograms per animal) plus progesterone (in the range from 0.0 to 2.4 mg per animal). It was found that the higher the dosage of estradiol and progesterone used, the more complete the precopulatory behavioral pattern that was induced. Further, the same level of sexual responsiveness was achieved by various combinations of both hormones used. The dose-response relationships are less complicated in prepubertally ovariectomized females in comparison with those spayed as adults. Finally, the most complete pattern, characterized by ritualized darting, was not achieved at all.