Effects of neonatal intracerebral implantation of sex steroids on sexual behaviour, social play behaviour and gonadotrophin secretion.

Female rats were intracerebrally implanted with testosterone propionate (TP) or 5 alpha-dihydrotestosterone (DHT) on the 3rd day of life. After both treatments, prepuberal social play behaviour was significantly enhanced as compared to control females and did not differ from that recorded in males. In contrast, intracerebral implantation of oestradiol benzoate (OB) at the same day of age had no effect on the frequency with which females engaged in social play. DHT, which is not aromatizable to oestrogen, showed a significant male-type organizational effect also on sexual orientation but not on the organization of gonadotrophin secretion pattern and hence on ovarian weight. On the other hand, OB displayed in a dose-dependent manner a significant male-type organizational effect on gonadotrophin secretion resulting in an anovulatory syndrome with significantly decreased ovarian weights due to failure of corpus luteum formation as well as on male-type sexual orientation. The results suggest that different sex hormones (oestrogens and/or androgens) are responsible for the sex-specific brain differentiation of gonadotrophin secretion, sexual orientation and gender role behaviour.