PROGESTERONE EFFECTS ON THE ACQUISITION OF CONDITIONED AVOIDANCE RESPONSES AND OTHER MOTORIC BEHAVIORS IN INTACT AND OVARIECTOMIZED RATS

This study demonstrates a significant impairment in the acquisition of conditioned avoidance responses in female rats during their estrus ph ase. Progesterone (PROG 5 mg) injected 6 h prior to the test, signific antly enhanced the performance exhibited by rats at estrus, but not at diestrus. In ovariectomized rats, the acquisition of conditioned avoi dance responses was similar to the exhibited during diestrus and this behavior was depressed by a single dose of estradiol benzoate (EB 2 mu g) injected 48 h prior to the test. PROG antagonized the avoidance de pression induced by EB, but it was not able to induce changes in the a cquisition of conditioned avoidance response in ovariectomized rats wi thout EB pretreatment. Estradiol appears to be the principal ovarian s teroid modulating the acquisition of an avoidance task, whereas PROG s eems to have a secondary role in this behavior, regulating the actions of estradiol on the brain. PROG failed to induce consistent changes i n some spontaneous motor behaviors in intact and ovariectomized rats.