Effect of estrogen on the lordosis-inhibiting action of ketanserin and SB 206553.

The effects of the 5-HT(2A/2C) receptor antagonist, ketanserin, and the 5-HT(2C) receptor antagonist, SB 206553, on lordosis behavior were investigated in ovariectomized rats hormonally primed with estradiol benzoate (EB) (0.5 or 25 microg) and progesterone (500 microg). Both ketanserin and SB 206553 inhibited lordosis behavior after infusion into the ventromedial nucleus of the hypothalamus (VMN), but ketanserin was slightly more effective than the 5-HT(2C) receptor antagonist. Either drug was more effective in rats primed with 0.5 microg EB than in rats hormonally primed with 25 microg EB. These findings support the suggestion that estrogen may enhance functioning of the 5-HT(2) receptor family and thereby protect against the 5-HT(2) receptor antagonists. These data are consistent with prior suggestions that estrogen modulates functioning of 5-HT(2) receptors within the VMN and that 5-HT(2) receptors play a facilitatory role in the modulation of female rat lordosis behavior.