Systemic ICI 182,780 alters the display of sexual behavior in the female rat

The present study investigates the effects of the antiestrogen ICI 182,780 (ICI) on the display of sexual behaviors in female rats. ICI 182,780 is a p ure anti-estrogen and when given systemically, ICI is thought to act only i n the periphery, and is not believed to cross the blood brain barrier. The present study examines the effects of ICI on sexual receptivity and on pace d mating behavior following treatment with estradiol benzoate (EB) and prog esterone (P) (Experiment 1) or with EB alone (Experiment 2). In Experiment 1, ICI (250.0 mug) did not affect the display of receptivity or paced matin g behavior induced by EB and P. In contrast, in Experiment 2 female rats re ceiving EB alone displayed a decrease in the level of sexual receptivity fo llowing treatment with 500.0 and 750.0 mug ICI (but not 250.0 mug ICI). In addition, in Experiment 2 EB-treated female rats receiving 250.0 mug ICI sp ent more time away from the male rat following an intromission and were mor e likely to exit from the male compartment following a mount. Last, ICI had potent antiestrogenic effects on vaginal cytology (Experiment 2) and on th e uterus (Experiments 1 and 2). The present study supports a role for perip heral estrogen receptors in sexual receptivity and paced mating behavior an d suggests that estrogen receptor activation may decrease the aversive sens ation associated with sexual stimulation. (C) 2001 Academic Press.