title: Sympathetic sprouting and changes in nociceptive sensory innervation in the glabrous skin of the rat hind paw following partial peripheral nerve injury.
abstract: Previous studies have suggested that sympathetic sprouting in the periphery may contribute to the development and persistence of sympathetically maintained pain in animal models of neuropathic pain. In the present study, we examined changes in the cutaneous innervation in rats with a chronic constriction injury to the sciatic nerve. At several periods postinjury, hind paw skin was harvested and processed by using a monoclonal antibody against dopamine-beta-hydroxylase to detect sympathetic fibers and a polyclonal antibody against calcitonin gene-related peptide to identify peptidergic sensory fibers. We observed migration and branching of sympathetic fibers into the upper dermis of the hind paw skin, where they were normally absent. This migration was first detected at 2 weeks, peaked at 4-6 weeks, and lasted for at least 20 weeks postlesion. At 8 weeks postlesion, there was a dramatic increase in the density of peptidergic fibers in the upper dermis. Quantification revealed that densities of peptidergic fibers 8 weeks postlesion were significantly above levels in sham animals. The ectopic sympathetic fibers did not innervate blood vessels but formed a novel association and wrapped around sprouted peptidergic nociceptive fibers. Our data show a long-term sympathetic and sensory innervation change in the rat hind paw skin after the chronic constriction injury. This novel fiber arrangement after nerve lesion may play an important role in the development and persistence of sympathetically maintained neuropathic pain after partial nerve lesions.
authors.affiliation: Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec H3G 1Y6, Canada.
authors.forename: Laurene D
authors.initials: LD
authors.lastname: Yen
authors.forename: Gary J
authors.initials: GJ
authors.lastname: Bennett
authors.forename: Alfredo
authors.initials: A
authors.lastname: Ribeiro-da-Silva
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism; D002908:Chronic Disease; D020405:Dermis / Q000294:innervation / Q000503:physiopathology; D004195:Disease Models, Animal; D004299:Dopamine beta-Hydroxylase / Q000378:metabolism; D005528:Foot / Q000294:innervation / Q000503:physiopathology; D020439:Growth Cones / Q000378:metabolism / Q000648:ultrastructure; D007150:Immunohistochemistry; D008026:Ligation; D008297:Male; D009473:Neuronal Plasticity / Q000502:physiology*; D009619:Nociceptors / Q000166:cytology / Q000502:physiology*; D010148:Intractable Pain / Q000503:physiopathology*; D010523:Peripheral Nervous System Diseases / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012019:Reflex Sympathetic Dystrophy / Q000503:physiopathology; D020426:Sciatic Neuropathy / Q000503:physiopathology; D011984:Sensory Receptor Cells / Q000166:cytology / Q000502:physiology*; D012867:Skin / Q000294:innervation / Q000503:physiopathology; D017779:Sympathetic Fibers, Postganglionic / Q000166:cytology / Q000503:physiopathology*
chemical_list: D015415:Biomarkers; D004299:Dopamine beta-Hydroxylase; D015740:Calcitonin Gene-Related Peptide