Cholinergic-androgenic interaction in the regulation of male sexual behavior in rats

It is well known that testosterone (T) plays a major role in the adequate expression of male sexual behavior. On the other hand, the stimulation of central muscarinic receptors with oxotremorine (OXO), a specific agonist, facilitates the expression of masculine sexual behavior in rats. In this study, we analyzed the relationship between T and the cholinergic system, recording the effect of OXO administration on masculine sexual behavior in gonadectomized rats, before and after receiving T treatment. Sexually experienced and unexperienced male rats were gonadectomized and periodically tested for sexual behavior. Once this behavior was absent or drastically reduced, males were treated with OXO or saline and sexual behavior was assessed. 112 or 167 days later, animals were treated daily with T during 21 days, recording the response to OXO in days 12 and 21. Sexual behavior decreased more rapidly after gonadectomy in inexperienced males. OXO administration did not improve sexual performance in either group. The administration of T rapidly restored sexual behavior of experienced males: recovery of inexperienced males was slower. In the presence of T, OXO administration exerted a facilitative effect on sexual performance of both groups. These results suggest that the facilitative effect of muscarinic stimulation on sexual behavior requires the presence of testosterone.