Effect of testosterone on intracavernous pressure elicited with electrical stimulation of the medial preoptic area and cavernous nerve in male rats.

We studied the effects of castration and testosterone (T) replacement on intracavernous pressure (ICP) elicited with electrical stimulation of the medial preoptic area (MPOA) and cavernous nerve (CN) in male rats. We measured the ICP during electrical stimulation of the MPOA and CN in castrated male rats with and without testosterone replacement. The experimental group consisted of 20-week-old male rats at 2 weeks (n=8), 4 weeks (n=8) and 8 weeks (n=8) after castration, and at 8 weeks after castration with T replacement (n=4). Intact 20-week-old rats (n=8) served as controls. The erectile response was expressed as the ICP/blood pressure (BP) ratio. The ICP/BP ratios during CN stimulation of the animals at 2, 4, and 8 weeks after castration were significantly lower than those of the intact animals. However, the erectile responses were not eliminated. In contrast to these peripherally evoked responses, erectile responses elicited by electrical stimulation of the MPOA were eliminated following castration. After testosterone replacement, both erectile responses were restored. Testosterone plays important roles in both the central and peripheral neural pathways for the maintenance and restoration of erectile capacity. The central control of erection shows more extensive changes following testosterone replacement than the peripheral control.