Effects of 17 beta-hydroxy-17 alpha-methyl-estra-4,9,11-triene-3-one (R 1881): evidence for direct involvement of androgens in the defeminization of behaviour in rats.

The synthetic androgen 17 beta-hydroxy-17 alpha-methyl-estra-4,9,11-triene-3-one (methyltrienolone, R 1881) binds specifically and with high affinity to androgen receptors and is presumably not metabolized into either the less potent androgens or into oestrogens. Because of these intrinsic properties, R 1881 can be used to investigate the possibility of a direct androgen involvement in the development of sexual behaviour. Females, at birth, were implanted with silicone elastomer capsules containing R 1881, testosterone, dihydrotestosterone or cholesterol for 10 days, or given daily injections of 100 micrograms hormone for 5 days. Neonatal treatment with R 1881 inhibited the capacity of female rats to show female mating behaviour when given ovarian hormones in adulthood; both implants and injections caused a similar reduction in receptive and proceptive behaviours. Testosterone, given as implants, caused almost complete defeminization, while injecting the hormone had a partial inhibition on mating responses. Dihydrotestosterone had no appreciable effect upon the development of behaviour. Thus, an androgen, R 1881, which is presumed not to be aromatized to oestrogens, has the potential to cause defeminization of mating and proceptive behaviour in female rats.