Differential effects of perinatal androgen treatment on sexually dimorphic characteristics in rats.

Rats were treated with testosterone propionate (TP) or oil (O) beginning in midgestation (group TTT), late gestation (group OTT), neonatally (group OOT), or were left untreated until adulthood (group OOO). At 40 days of age all animals were gonadectomized, received implants of TP in silastic capsules, and were tested in subsequent weeks for masculine copulatory behavior and ex copula phallic responses. Postmortem measures were taken of genital structures and of sexually dimorphic spinal nuclei. Males treated perinatally with androgen were unaffected or exhibited reduced masculinization except on two measures, i.e., number of penile flips and number of cells in the dorsolateral motor nucleus of the lumbar spinal cord, which reflected virilization greater than in normal males. All perinatally androgenized females showed virilization on almost every measure taken of their morphology and behavior. Relative to OOO females, the greatest increases in masculinization were evident in OOT and OTT females. No additional masculinization was detected in TTT females. Only among the TTT rats were males not reliably more masculine than females, but that usually was due to the reduced masculinization of TTT males. Four broad classes of influence characterized the effects of perinatal androgen treatment; these classes may reflect differences in the developmental courses of the variables measured.