Inhibition of the ejaculatory reflex in B6D2F mice by testosterone propionate

Hormonal restoration of masculine sexual behavior in long-term castrated B6D2F1 mice

In contrast to the facilitative effects reported for other rodents, testosterone treatment at the time of castration previously was reported to inhibit masculine sexual behavior in male B6D2F1 mice. Males of this genotype vary in their behavioral response to castration. Some castrates retain sexual behaviors for many weeks after surgery, whereas others do not. In the present study, we sought to determine the effects of exogenous steroid hormone treatment on castrated B6D2F1 mice that had ceased to show copulatory behavior. Testosterone propionate and estradiol benzoate restored copulatory behavior to precastration levels in B6D2F1 males that did not retain sexual behaviors after castration.

Differential sexual activity of isolated and grouped male mice despite testosterone administration

In Experiment 1, adult male C57 mice were castrated, housed individually or in groups of four, and repeatedly injected with either of two doses of testosterone. Control mice were sham-castrated, individually or group housed, and injected with oil vehicle. In repeated tests of sexual behavior with receptive females, isolated males in all surgery-dose combinations showed significantly more mounts and intromissions than did their group-housed counterparts. Ejaculations were fully restored by testosterone in castrated grouped males but not in castrated isolated males. In Experiment 2, administration of either of two doses of testosterone failed to elevate the sexual behavior of intact group-housed males. These experiments show that housing with other males depresses all major measures of sexual behavior, and suggest that this is probably independent of testicular hormones.

The genetics of hormonal influences on male sexual behavior of mice and rats

This review focuses on the intersection of genes and hormones as they relate to the development of male sexual behavior. Three major hypotheses are discussed: (1) Some differences in adult male sexual behavior are due to gene differences that influence brain differentiation. Genes that influence brain differentiation may do so by affecting the elaboration of testosterone (i.e., H-Y antigen) or the sensitivity to testosterone (i.e., Tfm mutation and autosomal variations) during neonatal and/or prenatal life. (2) Some differences in male sexual behavior are due to gene differences that influence adult levels of testosterone or sensitivity to testosterone and its metabolites. (3) There is a gene(s) on the Y chromosome that influences the development of sexual behavior that is associated with the arousal mechanism. A possible hormonal mechanism of this Y chromosomal gene(s) is discussed.