Experience modulates the influence of gonadal hormones on sexual orientation of male rats.

The aim of this study was to investigate whether heterosexual experience influences the male's partner preference and the role of gonadal hormones, including several androgens and estradiol, on female-oriented behavior. In the first experiment, the animals were exposed to a four-stimuli test situation including a sexually active male, a castrated male, an estrous female, and an ovariectomized (ovx) female. Castrated naive and experienced male rats were implanted with either testosterone (T), estradiol (E2), or an empty tubing (blank) and compared to intact naive and experienced male rats. None of the naive animals, whether castrated or intact, showed a consistent preference for any of the four stimuli. Whereas when sexually experienced, only intact and T-treated males showed a female-oriented preference. In the second experiment, the animals were allowed to choose between an active male and an estrous female. Castrated naive male rats were implanted with either T, E2, or DHT, or injected daily SC with the synthetic nonaromatizable androgen, methyltrienelone (R 1881). Two groups of intact males, one consisting of experienced and the other of naive animals, were also included in this experiment. The experienced intact males showed a significant preference for the estrous female, while the intact naive males showed no preference for either of the two stimuli. After the animals had gained heterosexual experience, intact and androgen-treated males showed a significant preference for the female. Neither the administration of R 1881 nor E2 promoted a female-oriented behavior.(ABSTRACT TRUNCATED AT 250 WORDS)