Chronic testosterone enanthate or estradiol benzoate affects sexual behavior and motivation in Long-Evans rats tested...

The present study tested the effects of chronic testosterone enanthate (TE) or estradiol benzoate (EB) on sexual behavior and motivation in female or male Long-Evans rats, respectively. Sexually experienced gonadally intact female rats were treated with TE (4.5 mg/0.1 ml) or oil twice per week for five weeks, whereas sexually experienced gonadally intact male rats were treated with EB (10 μg/0.1 ml) or oil daily for 28 days. On the last day of treatment, subjects were tested for partner preference, whereby subjects could choose to spend time near (no-contact phase) or with (contact phase) either a male or female stimulus. TE-treated females spent less time with the male stimulus during the no-contact phase, but less time with the female stimulus during the contact phase, compared to hormone-primed controls. TE-treated females displayed fewer solicitation behaviors than controls. TE treatment continued for 2 weeks after mating to monitor vaginal estrus. TE-females entered estrus, albeit less frequently than controls. At the end of exposure, body weight was greater, but ovarian weight was lower in TE-treated females than in controls. Conversely, EB-treated males spent more time with the male stimulus and less time with the female stimulus than controls during the contact phase. EB-treated males displayed fewer mounts and took longer to display their first mount. Testes and body weight were lower in EB-treated males than in controls at the end of the treatment period. These results add to our understanding of the effects of opposite-sex hormones on sexual behavior and reproductive physiology using an animal model.