The effect of phosphodiesterase-5 inhibitor and extracorporeal shock wave on cavernous nerve stimulation-induced intracavernous pressure increase in the diabetic rat

Purpose: Diabetes mellitus (DM) is a risk factor for erectile dysfunction. Low-intensity extracorporeal shock wave (LI-ESW) has been used for the treatment of erectile dysfunction (ED). Clinically, phosphodiesterase-5 (PDE5) inhibitor is the first-line treatment for male patients with ED. Therefore, the aim of this study was to investigate whether there was a synergistic effect of PDE5 inhibitor and LI-ESW on penile erection in the DM rats.

Materials and Methods: Streptozotocin (STZ)-induced DM rats were used. Six groups of experimental animals were designed as following: LI-ESW (0.05 mJ/mm² ) was delivered by a special probe (6 mm) to penile base and mid-shaft, respectively 400 shocks (group 1), 800 shocks (group 2), and 0 shock (group 3, sham control group), respectively twice a week for 2 weeks. The same LI-ESW experiment is executed in DM rats with daily feeding sildenafil 0.1 mg/0.2 ml via oral-gastric tube for 4 weeks (group 4, 5, 6). Then electrical stimulation of cavernous nerve (CN) and major pelvic ganglion (MPG), respectively with parameters (5 and 7.5 V, 20 Hz, 2 ms, 1 minute) 2 weeks after 2-week LI-ESW in each of the six groups of rats, and the intracavernous pressure (ICP) was monitored via a 26-gauge needle inserted into the corpus cavernosum. The amount of ICP increase was the difference between the peak ICP and resting ICP.

Results: There were a significant greater amount of ICP increase after CN stimulation with 5 and 7.5 V in the group 1 (7.5 V: 62.3 ± 6.7 mmHg, p = 0.041) and group 2 (7.5 V: 69.5 ± 6.9 mmHg, p = 0.015) compared with group 3 rats (sham control, 7.5 V: 40.7 ± 5.5 mmHg), respectively. A significant greater amount of ICP increase after MPG stimulation with 5 and 7.5 V were noted in the group 1 (7.5 V: 70.0 ± 4.6 mmHg, p = 0.002) and group 2 (7.5 V: 70.0 ± 6.8 mmHg, p = 0.004) compared with group 3 rats (7.5 V: 37.7 ± 4.6 mmHg), respectively. There were no significant difference of amount in ICP increase after CN stimulation with 5 and 7.5 V among group 4 (7.5V: 66.0 ± 4.0 mmHg), 5 (7.5V: 61.7 ± 6.1 mmHg) and 6 (7.5V: 55.7 ± 5.6 mmHg) [p = 0.286]. No significant difference amount of ICP increase after MPG stimulation with 5 and 7.5 V among group 4 (7.5V: 67.0 ± 5.4 mmHg), 5 (7.5V: 75.3 ± 5.7 mmHg), 6 (7.5V: 58.0 ± 4.3 mmHg)[p = 0.286]. There were no significant greater amount of ICP increase after CN stimulation with 5 and 7.5 V between shockwave groups with and without daily feeding sildenafil (group 4 vs. 1, group 5 vs. 2, group 6 vs. 3).

Conclusion: The results suggest that extracorporeal shock wave may have an enhancing effect on CN or MPG stimulation-induced intracavernous pressure increase in DM rat. Combined sildenafil with LI-ESW may not have a synergistic effect on penile erection in the diabetic rats.