Female gonadal hormones, mild restraint, and male preference

The partner preference paradigm was used to test the hypothesis that mild restraint reduced sexual motivation of female rats. Ovariectomized rats were primed with 10 mu g estradiol benzoate or estradiol benzoate and 500 mu g progesterone. Additional rats were injected with sesame seed oil. These three groups of rats (oil-oil, estradiol benzoate-oil, or estradiol benzoate-progesterone; OO, EO, EP) were placed for 10 min in an arena, the ends of which enclosed either a sexually active male or an ovariectomized, unprimed female. Time spent near the sexually active male relative to time spent near either stimulus animal was used as the index of male preference. As expected, hormonal treatment significantly increased male preference. After this first 10 min interval, females were returned to the home cage or restrained for 5 min in a Decapicone (R). Thereafter, male preference was recorded for another 10 min. Consistent with the first 10 min period, EP rats spent significantly more time near the male than did OO rats while EO rats were intermediate. There was no effect of restraint, but there was a significant increase in self-grooming. These findings contrast with previous studies and allow the suggestion that a brief, mild restraint fails to influence the female's sexual motivation. The implications of these findings are discussed. (C) 2008 Elsevier Inc. All rights reserved.