Suppression of the development of female hamster behaviour by implants of testosterone and non-aromatizable androgens administered neonatally.

Testosterone in its free form, and dihydrotestosterone (DHT) and androsterone, both androgens which are not aromatizable to oestrogen, injected in oil during the neonatal period have been reported not to modify the development of female sexual behaviour. This failure might be due to the short period of activity of these substances when injected in liquid vehicles. In the current study, a Silastic pellet containing 9% of its weight of testosterone, androsterone, or DHT was implanted subcutaneously in 42 female and 38 neonatally castrated male hamsters on day 2 of life and removed on day 10. Pellets of pure Silastic were implanted in 36 control animals. Males were gonadectomized on day 5 and females on day 45. Female sexual behaviour induced by oestradiol benzoate and progesterone was measured in a series of 10-min mating tests with vigorous males, starting at 55 days of age. The duration of lordosis was consistently reduced below control levels in females implanted with testosterone, DHT, and androsterone, and in males, with testosterone and DHT. Thus the free form of testosterone, and some non-aromatizable androgens, when present for a sufficiently long period after birth, can permanently suppress development of female reproductive behaviour.