GROWTH-HORMONE ENHANCES REGENERATION OF NITRIC-OXIDE SYNTHASE-CONTAINING PENILE NERVES AFTER CAVERNOUS NERVE NEUROTOMY IN RATS

Purpose: As growth hormone has been reported to improve nerve regenera tion, we studied the effect of rat growth hormone (GH) on the regenera tion of nitric oxide synthase (NOS)-containing penile nerves and the n eurons in the pelvic ganglia after unilateral cavernous nerve neurotom y in rats. Materials and Methods: Male rats were divided into three gr oups: sham operation (n = 14); unilateral neurotomy of a 5 mm. segment of the cavernous nerve (n = 14) with subsequent injection of buffer s olution only; and unilateral neurotomy with GH injection (n = 14). Ele ctrostimulation of the intact cavernous nerve was performed at 1 and 3 months. Nicotinamide adenine dinucleotide phosphate (NADPH) diaphoras e staining was used to identify NOS in penile nerve fibers of the mid- shaft segment and in neurons of the pelvic ganglia. Results: One month after unilateral neurotomy, both the buffer alone and GH-treated grou ps showed a significant decrease in NOS-containing nerve fibers in the dorsal and intracavernosal nerves on the side of neurotomy. At 3 mont hs, the number of NOS-containing nerve fibers in the buffer alone grou p did not increase, while the OH-treated group showed a significant in crease. In the OH-treated group at 3 months, more NOS-positive neurons in the pelvic ganglia were found on the intact side than on the side of neurotomy (p <0.034), indicating that the regeneration derives from pelvic ganglion neurons on the intact side. Furthermore, electrostimu lation in the OH-treated group revealed a greater maximal intracaverno sal pressure and a shorter latency period at 3 months than in those gi ven buffer alone. Conclusions: Our results show that GH injection sign ificantly enhances the regeneration of NOS-containing fibers in the do rsal and intracavernosal nerves after unilateral cavernous nerve injur y. We believe that GH administration may present a new and more physio logic approach to the treatment of erectile dysfunction after radical pelvic surgery.