Brain androgen-inducible aromatase is critical for adolescent organizationof environment-specific social interaction in male rats

Previous observations have indicated that specific behavioral responses to anxiogenic stimuli emerge over adolescent development in male rats and that gonadal androgens during puberty are essential for this emergence. The obj ective of the current study was to evaluate mechanisms via which androgens might be organizing the brain during adolescence for appropriate mature ada ptive responses. Male rats were exposed to fadrozole (an aromatase inhibito r, 5 mg/kg), flutamide (an androgen receptor antagonist, 10 mg/kg), or MK-4 34 (a 5 alpha-reductase inhibitor, 10 mg/kg) from day 29 to 60 and tested f or environment-specific social interaction (SI) at 60 days of age. The emer gence of adult-typical SI was impaired by exposure to the aromatase inhibit or and to the antiandrogen, whereas exposure to the 5 alpha-reductase inhib itor was without effect. peripheral indices of drug effects indicated that the respective mechanisms had been altered by the different compounds. Thes e results suggest that testosterone induction of aromatase is critical for the organization of mature SI behavior in male rats over adolescent develop ment. (C) 1999 Academic Press.