Department of Physiology, Royal Veterinary College, London, NW1 OTU
(Received 11 November 1974)
Castration in the rat causes an increase in the post-ejaculatory refractory period, often before ejaculation declines. This indicates a central effect of androgen withdrawal and can be prevented only by treatment with aromatizable androgens (Parrott, 1975), suggesting that the effect involves conversion of androgen to oestrogen. In support of this suggestion, two androgen/oestrogen intermediates, 19-hydroxytestosterone (Parrott, 1974) and 19-hydroxyandrostenedione (Parrott, 1975), and oestrogen (Davidson, 1969; Parrott, 1975) maintain normal refractory periods in castrated rats. This report describes the behavioural action of 19-nortestosterone, an androgen without a 19-methyl group. Some androgens induce receptivity in ovariectomized rats when combined with progesterone. This effect is inhibited by antioestrogens (Whalen, Battie & Luttge, 1972), implicating the involvement of aromatization. Because of this, 19-nortestosterone was first studied in female rats.
In week 1, 22 ovariectomized Sprague-Dawley (MRC) rats received 10 μg oestradiol benzoate