Estradiol modulation of the hyperphagia induced by the 5-HT1A agonist, 8-OH-DPAT

Ovariectomized rats were primed with sesame oil or estradiol benzoate followed 48 h later by either sesame oil or progesterone. Four hours later, rats were treated with either saline or 0.25 mg/kg 8-hydroxy-2-9(di-n-propylamino)tetralin (8-OH-DPAT). Rats were allowed to eat for 4 h after this final treatment. Animals in all hormonal conditions showed hyperphagia following 8-OH-DPAT. However, the hyperphagia was significantly attenuated by pretreatment with estradiol benzoate. There was no effect of progesterone on the hyperphagic response. These results suggest that previous findings of an estrous cycle modulation of the hyperphagic response to 8-OH-DPAT arise from the modulatory effects of estradiol, and not progesterone, during the female reproductive cycle.