Autonomic control of penile erection: modulation by testosterone in the rat.

The role of testosterone on peripheral autonomic control of penile erection was studied in rats. Erectile response to cavernous nerve stimulation was measured by intracavernous pressure associated with arterial blood pressure monitoring in anesthetized adult males. Comparison was performed between control (Co), castrated (Ox) and castrated, testosterone-replaced (OxT) rats. Ox rats exhibited smaller erectile responses. Testosterone replacement restored these responses in OxT rats. To identify the peripheral target of testosterone, postganglionic neurons of the major pelvic ganglion, innervating the corpora cavernosa through the cavernous nerves, were separated from the spinal cord by preganglionic axotomy of the pelvic nerves in three other groups of rats (PNx). Erectile response was unchanged in PNx rats, decreased in OxPNx more than in Ox rats, and restored by testosterone replacement (OxPNxT rats). We ruled out the participation of a somatic component in the erectile response in this model as there was no difference between curarized and Co rats. We infer that testosterone enhances the erectile response of cavernous nerve stimulation, acting peripherally to the spinal cord. Arguments are provided that the sites of action for testosterone or its metabolites are situated on neurons rather than on penile erectile tissue. Proerectile postganglionic parasympathetic neurons seem to be the exact target for gonadal steroids.