Sex differences in behavioural androgen sensitivity: possible role of androgen metabolism

ABSTRACT Masculine sexual behaviour was induced in castrated sexually inactive but experienced male rats by testosterone-filled constant-release implants or daily injections of the synthetic androgen 17β-hydroxy-17α-methyl-estra-4,9,11-triene-3-one (methyltrienolone, R 1881), which resists metabolism by target organs. Feminization of the hepatic androgen metabolism by subcutaneous implantation of osmotic minipumps, which delivered a constant amount of human GH, did not affect the behavioural response of castrated rats to testosterone. Testosterone implants were only minimally effective in inducing male behaviour in ovariectomized female rats, but R 1881 was as effective in stimulating male behaviour in females as in males. Testosterone-treated but not R 1881-treated females showed pronounced female sexual behaviour in response to progesterone treatment despite the absence of measureable amounts of oestradiol-17β in peripheral blood. The results provide evidence that masculine sexual behaviour can be activated by an androgen in the absence of oestrogenic stimulation and suggest that the sex difference in the behavioural response to testosterone may be due to a sex difference in the metabolism of androgens by the brain. J. Endocr. (1984) 100, 245–248

EFFECT OF PROSTAGLANDIN E2 ON MASCULINE SEXUAL BEHAVIOUR IN THE RAT

Intracerebral infusion of prostaglandin E2 (PGE2) facilitated copulatory behaviour of longterm castrated rats. Castrated rats were given daily systemic injections of testosterone propionate (50 pg) or oil vehicle, and then 30 min before behavioural testing they received an intrahypothalamic infusion of either PGE2 or saline. Rats receiving PGE2 in addition to systemic testosterone showed more copulatory behaviour than those receiving PGE2 or testosterone alone.

POSSIBLE INVOLVEMENT OF CYCLIC AMP IN REGULATION OF MASCULINE SEXUAL BEHAVIOUR BY TESTOSTERONE

SUMMARY Experiments were carried out to assess the possible involvement of cyclic AMP in the regulation of masculine sexual behaviour by testosterone in the laboratory rat. Doses of testosterone propionate which were ineffective in maintaining or inducing male sexual behaviour were potentiated by concurrent administration of theophylline. Since removal of the adrenal glands had no effect on this potentiation, the possibility that theophylline increased adrenal androgen secretion and thereby influenced sexual behaviour, can be ruled out. A major effect of theophylline is to increase levels of cyclic AMP by inhibiting the enzyme which inactivates this nucleotide. These results suggest that cyclic AMP may play a mediating role in the regulation of masculine sexual behaviour by testosterone.