Effects of testosterone propionate and dihydrotestosterone on penile morphology and sexual reflexes of spinal male rats

Testosterone propionate (TP) has a quantitative influence on sexual reflexes mediated at the spinal level in male rats. The possibility that this influence reflects the direct action of androgen on neural elements in the cord, rather than on sensory receptors in the penis was examined indirectly by the use of dihydrotestosterone (DHT). Spinal castrated male rats maintained initially on TP and then switched to DHT showed a significant decline in sexual reflexes paralleling the decline of another group of spinal rats receiving no hormone after initial TP treatment. Yet the number of penile papillae and weight of the penile shaft for the DHT subjects were not significantly different from these measures of penile morphology in a third group of subjects receiving continuous TP and in which reflexes did not decline. These and other observations are consistent with the hypothesis that neural elements within the spinal cord, related to the mediation of the ejaculatory pattern in intact male rats, are directly influenced by gonadal androgen.