Effects of neonatal testicular hormones on preference behaviour in the rat

The effects of neonatal testicular hormones on preference behaviour for an oestrous female rat were investigated. A residential maze was used in which the position of the animals was registered continuously without disturbing them. Two experiments are described. In the first experiment adult male rats which had been castrated within 24 h of birth were given testosterone (T), dihydrotestosterone (DHT) or oestradiol (E2) in a subcutaneous silastic implant. The T- and E2-treated males showed preference for an oestrous female rat over an anoestrous female. The DHT-treated animals showed no interest in a female conspecific, irrespective of her hormonal state. In the second experiment females spayed in adulthood were given a T-containing silastic implant. They showed preference for the oestrous female, like intact males. Removal of the T-implant caused this preference to disappear, while locomotor activity was not affected. It is concluded that neonatal testicular hormones have little effect on adult sociosexual preference behaviour.