Male rats were treated daily with 100 microgram of the anti-oestrogen
ethamoxytriphetol (MER-25) or oil during the first 10 days of life and tested for
lordosis behaviour and mounting behaviour as intact adults, after
castration and after
castration and
oestradiol benzoate or
testosterone propionate treatment. The MER-25-treated rats showed higher levels of
lordosis behaviour than oil-treated rats in all four treatment groups. Under each of these endocrine conditions, except after
castration alone, the MER-25-treated rats showed a reduced capacity to ejaculate. Treatment of the neonatal rat with
MER-25 reduced
body weight in adulthood but did not change the weight of the accessory sexual glands, the testes, the number of cornified papillae on the glans penis or plasma
testosterone concentrations during development. The response of the accessory sexual glands and cornified papillae on the glans penis to treatment with
oestradiol benzoate or
testosterone propionate after
castration in adulthood was unaffected by treatment with
MER-25. It is suggested that formation of oestrogen in the neonatal male rat brain from
testosterone in the circulation inhibits the capacity to show
lordosis behaviour and facilitates the capacity to ejaculate in response to ejaculate in response to
gonadal hormone treatment in adulthood.