AB211. Effect of early chronic low-dose tadalafil administration on erectile dysfunction after cavernous nerve injury in the rat model

OBJECTIVE: To investigate the effect of early chronic tadalafil administration on erectile dysfunction after cavernous nerve (CN) injury in the rat model. METHODS: Using the CN crush injury model, animals were divided into four groups: no CN injury (sham), bilateral CN injury exposed to either no tadalafil (control) or tadalafil at a dose (2 mg/kg) daily postoperation for 4 weeks, and normal group. At the time point, we assessed erectile function by apomorphine test, measurement of maximum intracavernosal pressure (ICP)/mean arterial pressure (MAP) ratio with major pelvic ganglion (MPG) electrical stimulation. For the histological analyses, the mid-shaft of penis were harvested. Immunohistochemical antibody staining was performed for nNOS and the numbers of nNOS-positive nerve fibers were recorded. RESULTS: Penile erection was observed in 50% (6/12) of the rats for (1.13±0.92) times within 30 min in control group, as compared with 0% (0/11) of the rats for (0.00±0.00) times in CN crush group (P<0.05), and 100% (10/10) of the rats for (2.03±0.97) times in sham group (P<0.05), and 100% (10/10) of the rats for (2.36±1.02) times in normal group (P<0.05). No significant differences in ICP/MAP ratio before MPG electrical stimulation in 4 groups (P>0.05), while ICP/MAP ratio after MPG electrical stimulation of control group was significantly higher than that of CN crush group (P<0.05), but significantly lower than that of sham group (P<0.05) and normal group (P<0.05). The numbers of nNOS-positive nerve fibers was significantly larger in control group than in CN crush group (54.11±5.02 vs. 21.34±3.17, P<0.05), but was significantly smaller than that of sham group (76.48±8.24, P<0.05) and normal group (81.09±7.25, P<0.05). CONCLUSIONS: Early chronic low-dose tadalafil administration on erectile dysfunction after CN injury contributes to restoration of erectile function.