title: Partial sciatic nerve ligation induced more dramatic increase of neuropeptide Y immunoreactive axonal fibers in the gracile nucleus of middle-aged rats than in young adult rats.
abstract: Neuropeptide changes in primary sensory neurons caused by partial nerve injury are likely involved in the development of neuropathic pain. In this study, using immunocytochemistry, we examined neuropeptide Y (NPY) expression in lumbar dorsal root ganglion (DRG) cells of young adult (2-3 months old) and middle-aged (8-10 months old) rats 4 weeks after partial sciatic nerve ligation (PSNL). Significantly higher NPY immunoreactivity was induced in the injured side DRG neurons, the dorsal horn and the gracile nuclei in middle-aged rats than in young rats. Using combined fluorescent dye tracing and NPY immunostaining, we found in middle-aged rats that 46% injured DRG neurons projected to the gracile nucleus and 45% of injured neurons were also NPY-IR, whereas 42% spared DRG neurons projected to the gracile nucleus and 18% of spared neurons were also NPY-IR. Thus PSNL induces NPY up-regulation in spared as well as injured DRG neurons, both contribute to the increased NPY immunoreactivity in the gracile nucleus in the middle-aged rats. The more dramatic increase of NPY in DRG neurons of middle-aged rats after PSNL shows that the responses to partial nerve injury are age-dependent, that suggests a possible relevance to the higher incidence of neuropathic pain in human middle age.
authors.affiliation: Department of Physiology, Faculty of Medicine, Queen's University, Kingston, Ontario, Canada. maweiy@douglas.mcgill.ca
authors.forename: W
authors.initials: W
authors.lastname: Ma
authors.forename: M A
authors.initials: MA
authors.lastname: Bisby
mesh_terms: D000375:Aging; D000818:Animals; D001370:Axonal Transport; D001369:Axons / Q000378:metabolism*; D005456:Fluorescent Dyes / Q000032:analysis; D005727:Ganglia, Spinal / Q000166:cytology / Q000378:metabolism; D007150:Immunohistochemistry; D008026:Ligation; D008297:Male; D008526:Medulla Oblongata / Q000166:cytology / Q000378:metabolism*; D009478:Neuropeptide Y / Q000378:metabolism*; D020671:Posterior Horn Cells / Q000166:cytology / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012584:Sciatic Nerve / Q000293:injuries* / Q000503:physiopathology* / Q000601:surgery
chemical_list: D005456:Fluorescent Dyes; D009478:Neuropeptide Y