REGULATION OF BRAIN ANDROGEN RECEPTOR IMMUNOREACTIVITY BY ANDROGEN INPREPUBERTAL MALE FERRETS

During pubertal maturation, there is an increase in the number of andr ogen receptor-immunoreactive (AR-IR) cells in the preoptic area (POA), arcuate nucleus (ARC), medial amygdala (mAMY), and ventromedial hypot halamic nucleus (VMH) of the male ferret brain. In contrast, the numbe r of AR-IR cells in the bed nucleus of the stria terminalis (BNST) or lateral septum (ISEP) does not change with pubertal development. This experiment tested the hypothesis that the pubertal increase in AR-IR c ells in certain brain regions is the result of the pubertal increase i n circulating androgens. Prepubertal male ferrets were left intact or were castrated and treated daily (10 days) with s.c. injections of eit her oil, testosterone (T; 5 mg/kg), dihydrotestosterone (DHT; 5 mg/kg) , or estradiol (E; 10 mu g/kg). Brains were processed for AR immunocyt ochemistry, and the number of immunopositive cells was quantified in P OA, ARC, mAMY, VMH, BNST, and ISEP. Overall, castration reduced the nu mber of AR-IR cells below that seen in intact animals, and E administr ation did not restore AR-IR cell number. Treatment of castrates with a ndrogens restored numbers of AR-IR cells to those of intact animals in the BNST, ISEP, and VMH. However, AR-IR cell numbers were significant ly greater in androgen-treated castrates than in intact animals in POA , mAMY, and ARC. These data show that AR-IR cells in prepubertal male ferrets are sensitive to circulating levels of androgens, supporting t he hypothesis that the pubertal rise in T is responsible for the puber tal increase in the number of AR-IR cells in the POA, mAMY, and ARC.