The Action Mechanism of Growth Hormone on Regeneration of Nitiric Oxide Synthase(NOS)-containing Nerves after Cavernous Neurotomy in the Rat

Jung, Gyung Woo; Kwak, Jong Young; Kim, Joong Keun; Yoon, Jin Han

Abstract

PURPOSE: As growth hormone was reported to improve cavernosal nerve regeneration, we studied the action mechanism of growth hormone(GH) on the regeneration of nitric oxide synthase(NOS)-containing penile nerves after unilateral cavernous nerve neurotomy in rats.
MATERIALS AND METHODS
Male rats were divided into three groups: sham operation(n=10); unilateral neurotomy of a 5mm segment of the cavernous nerve(n=10) and unilateral neurotomy with GH injection(n=10). Electrostimulation of the intact cavernous nerve was performed at 1 and 3 months after operation. Nicotinamide adenine dinucleotide phosphate(NADPH) diaphorase staining was used to identify nNOS in penile nerve fibers of the mid-shaft segment. The gene expression for nNOS, insulin like growth factor(IGF)-I and nerve growth factor(NGF) were investigated in corporal tissue by reverse transcriptase-polymerase chain reaction(RT-PCR) using specific oligonucleotide primers.
RESULTS
Electrostimulation in the GH-treated group revealed a greater maximal intracavernosal pressure and a shorter latency period than in those given neurotomy alone at 3 months after operation. One month after unilateral neurotomy, both neurotomy alone and the GH-treated groups showed a significant decrease in NOS-containing nerve fibers in the dorsal and intracavernosal nerves on the side of neurotomy, however mRNA expression of nNOS and IGF-I showed a significant increase in GH-treated group. At 3 months, the number of NOS-containing nerve fibers in the neurotomy alone group did not increase while the GH-treated group showed a significant increase.
CONCLUSIONS
These results show that GH significantly enhances the regeneration of NOS-containing fibers in the dorsal and intracavernosal nerves after unilateral cavernous nerve injury via IGF-I.