Growth hormone enhances regeneration of nitric oxide synthase-containing penile nerves after cavernous nerve neurotomy in rats.
OBJECTIVE
As growth hormone has been reported to improve nerve regeneration, we studied the effect of rat growth hormone (GH) on the regeneration of nitric oxide synthase (NOS)-containing penile nerves and the neurons in the pelvic ganglia after unilateral cavernous nerve neurotomy in rats.


METHODS
Male rats were divided into three groups: sham operation (n = 14); unilateral neurotomy of a 5 mm. segment of the cavernous nerve (n = 14) with subsequent injection of buffer solution only; and unilateral neurotomy with GH injection (n = 14). Electrostimulation of the intact cavernous nerve was performed at 1 and 3 months. Nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase 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 groups showed a significant decrease in NOS-containing nerve fibers in the dorsal and intracavernosal nerves on the side of neurotomy. At 3 months, the number of NOS-containing nerve fibers in the buffer alone group did not increase, while the GH-treated group showed a significant increase. In the GH-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, electrostimulation in the GH-treated group revealed a greater maximal intracavernosal pressure and a shorter latency period at 3 months than in those given buffer alone.


CONCLUSIONS
Our results show that GH injection significantly enhances the regeneration of NOS-containing fibers in the dorsal and intracavernosal nerves after unilateral cavernous nerve injury. We believe that GH administration may present a new and more physiologic approach to the treatment of erectile dysfunction after radical pelvic surgery.
Department of Urology, University of California School of Medicine, San Francisco 94143-0738, USA.
G W
GW
Jung
E M
EM
Spencer
T F
TF
Lue
D000818:Animals; D013006:Growth Hormone / Q000502:physiology*; D008297:Male; D009416:Nerve Regeneration; D019001:Nitric Oxide Synthase; D010413:Penis / Q000201:enzymology / Q000294:innervation* / Q000502:physiology* / Q000601:surgery; D051381:Rats; D017207:Rats, Sprague-Dawley
D013006:Growth Hormone; D019001:Nitric Oxide Synthase