Regeneration of nNOS-containing nerve fibers in rat corpus cavernosum

OBJECTIVE: To investigate the effect of cavernous nerve injury on the nNOS-containing nerve fibers in corpus cavernosum. METHODS: Thirty-three male Sprague Dawley (SD) rats were randomly divided into 3 groups: sham-operated controls (n = 5) underwent pelvic exploration without transection of the cavernous nerve; unilateral injury group (n = 14) had their cavernous nerve cut on one side; and bilateral injury group (n = 14) underwent neurotomy on both sides. Corpora cavernosa were harvested at the 3rd week and 6th month after surgery. nNOS-positive nerve fibers were examined with streptavidin-peroxidase immunohistochemistry techniques (SP method). RESULTS: After bilateral ablation, the nNOS-positive nerve fibers were significantly decreased at the 3rd week (17 +/- 4) and remained so at the 6th month (16 +/- 4). For the unilateral injury group, the nNOS-positive nerve fibers were similarly decreased on the side of the neurotomy at the 3rd week (18 +/- 6), but by the 6th month, the number increased significantly (61 +/- 9) and approximated the level on the contralateral side (81 +/- 13). CONCLUSION: Following unilateral cavernous nerve ablation in rats, nNOS-containing nerve fibers regenerate 6 months after surgery. This regeneration process does not occur in animals with bilateral cavernous nerve injury, suggesting that during radical pelvic surgery, the cavernous nerve has to be preserved at least on one side in order to maintain the capacity for penile erection.