Play, copulation, anatomy, and testosterone in gonadally intact male rats prenatally exposed to flutamide.

The role of prenatal androgen on the differentiation of sexually dimorphic juvenile play and adult copulatory patterns was evaluated in male offspring of rats injected with 5 mg of the androgen receptor blocker flutamide (4'-nitro-3'-trifluoromethylisobutyranilide) from Days 11-21 of pregnancy. Rough-and-tumble play was incompletely masculinized in flutamide-exposed males at 31 days of age. The copulatory potential tested at 70 days of age was severely attenuated by prenatal flutamide. There was no ejaculatory behavior, low levels of intromissions, and depressed levels of nonintromittive mounting when the animals were tested while gonadally intact. Adult plasma levels of testosterone (T) were not different in flutamide-exposed males and controls, but testicular and epididymal weight, anogenital (AG) distance, and penile length were reduced. While reductions in intromittive mounting and ejaculatory behavior may be due to the abnormalities in the external genitalia, the incomplete masculinization of play and the reduction in nonintromittive mounting probably resulted from effects the androgen antagonist exerted on sexual differentiation of the central nervous system. These data suggest that androgen released prior to birth is needed for the full masculinization of juvenile play behaviors in the rat, just as it is for the adult copulatory pattern.