Specificity of testosterone and estradiol in the differentiating neonatal rat

Those components of sexual behavior characteristic of the adult intact male such as intromission and ejaculation, were inhibited in males receiving estradiol dipropionate within the first week of life. Neonatal treatment with testosterone propionate at corresponding ages did not disrupt the capacity for homotypic behavior when the males became adult. The expression of female behavior during adulthood was suppressed in female rats treated during a critical period of early postnatal life with testosterone propionate or estradiol dipropionate. Spermatogenesis was suppressed in males receiving the estrogen but not the androgen in early postnatal life, whereas ovulation was suppressed in females receiving the estrogen or androgen at corresponding periods. It was concluded that testosterone is compatible with the normal development of male sexual characteristics but that estradiol is not compatible with development of female sexual characteristics when administered during a critical period of differentiation. The specificity for androgen in adult males is postulated to be partly due to the presence of androgens during the critical period. The specificity for estrogen shown by females in adulthood is thought to be dependent upon the absence of estrogen and androgen during a corresponding developmental stage.