Cavernous nerve injury elicits GAP-43 mRNA expression but not regeneration of injured pelvic ganglion neurons

• Published in: Brain research 2003-10, Vol.986 (1), p.166-173
• Main Authors: Kato, Ryuichi, Kiryu-Seo, Sumiko, Sato, Yoshikazu, Hisasue, Shinichi, Tsukamoto, Taiji, Kiyama, Hiroshi
• Format: Article
• Language: English
• Subjects: Animals; Autonomic nerve; Biological and medical sciences; Biomarkers; Cavernous nerve; Erectile Dysfunction - genetics; Erectile Dysfunction - metabolism; Erectile Dysfunction - physiopathology; Fluorescent Dyes; Functional Laterality - physiology; Fundamental and applied biological sciences. Psychology; Ganglia, Autonomic - cytology; Ganglia, Autonomic - metabolism; GAP-43; GAP-43 Protein - genetics; Hypogastric Plexus - injuries; Hypogastric Plexus - metabolism; Hypogastric Plexus - physiopathology; Male; Motor control and motor pathways. Reflexes. Control centers of vegetative functions. Vestibular system and equilibration; Nerve injury; Nerve Regeneration - physiology; Neuronal Plasticity - physiology; Neurons - metabolism; Nitric Oxide - metabolism; Nitric Oxide Synthase - metabolism; Norepinephrine - metabolism; Pelvic ganglion; Penis - innervation; Rats; Rats, Wistar; Reaction Time - physiology; Recovery of Function - physiology; Regeneration; RNA, Messenger - metabolism; Stilbamidines; Tyrosine 3-Monooxygenase - metabolism; Vertebrates: nervous system and sense organs
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/S0006-8993(03)03249-9

Recovery of erectile dysfunction after cavernous nerve injury takes a long period. To elucidate this mechanism, unilateral cavernous nerve of male rat was cut, and the expression level of a nerve regeneration marker, the growth associated protein-43 (GAP-43) mRNA was evaluated by in situ hybridization and RT-PCR. While GAP-43 mRNA expression was transiently increased in the injured neurons of the major pelvic ganglion (MPG) at 7 days after nerve injury, continuous increase of GAP-43 mRNA was observed in the contralateral MPG from 7 days to 6 months after the nerve injury. Histochemical double-labeling studies for either neuronal NOS (nNOS) or tyrosine hydroxylase (TH) and the GAP-43 mRNA expression demonstrated that in injured MPG the transient up-regulation of GAP-43 mRNA was mainly seen in nNOS negative and/or TH positive neurons, suggesting non-parasympathetic post-ganglionic neurons, and also demonstrated that in contralateral MPG GAP-43 mRNA positive neurons were gradually increased in nNOS positive but TH negative neurons, suggesting parasympathetic post-ganglionic neurons. When a retrograde tracer Fluorogold (FG) was injected into the penile crus 7 days before histological experiments, FG-positive neurons were, if any, hardly seen in nNOS-positive neurons of the injured MPG for at least 6 months, whereas numerous FG-positive cells were seen in nNOS-positive neurons of the contralateral MPG. These results suggest that post-ganglionic projecting neurons of the intact side, which express increased GAP-43 mRNA, would be most likely to contribute to the recovery of the erectile function after unilateral cavernous nerve injury possibly by a plastic change such as nerve sprouting.