title: Chronic Compression of the Dorsal Root Ganglion Enhances Mechanically Evoked Pain Behavior and the Activity of Cutaneous Nociceptors in Mice.
abstract: Radicular pain in humans is usually caused by intraforaminal stenosis and other diseases affecting the spinal nerve, root, or dorsal root ganglion (DRG). Previous studies discovered that a chronic compression of the DRG (CCD) induced mechanical allodynia in rats and mice, with enhanced excitability of DRG neurons. We investigated whether CCD altered the pain-like behavior and also the responses of cutaneous nociceptors with unmyelinated axons (C-fibers) to a normally aversive punctate mechanical stimulus delivered to the hairy skin of the hind limb of the mouse. The incidence of a foot shaking evoked by indentation of the dorsum of foot with an aversive von Frey filament (tip diameter 200 μm, bending force 20 mN) was significantly higher in the foot ipsilateral to the CCD surgery as compared to the contralateral side on post-operative days 2 to 8. Mechanically-evoked action potentials were electrophysiologically recorded from the L3 DRG, in vivo, from cell bodies visually identified as expressing a transgenically labeled fluorescent marker (neurons expressing either the receptor MrgprA3 or MrgprD). After CCD, 26.7% of MrgprA3+ and 32.1% MrgprD+ neurons exhibited spontaneous activity (SA), while none of the unoperated control neurons had SA. MrgprA3+ and MrgprD+ neurons in the compressed DRG exhibited, in comparison with neurons from unoperated control mice, an increased response to the punctate mechanical stimuli for each force applied (6, 20, 40, and 80 mN). We conclude that CCD produced both a behavioral hyperalgesia and an enhanced response of cutaneous C-nociceptors to aversive punctate mechanical stimuli.
authors.affiliation: Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, School of Basic Medicine, Peking Union Medical College, Neuroscience Center, Department of Anatomy, Histology and Embryology, Beijing, China; Department of Anesthesiology, Yale University School of Medicine, New Haven, Connecticut, United States of America.
authors.forename: Tao
authors.initials: T
authors.lastname: Wang
authors.affiliation: Department of Anesthesiology, Yale University School of Medicine, New Haven, Connecticut, United States of America.
authors.forename: Olivia
authors.initials: O
authors.lastname: Hurwitz
authors.affiliation: Department of Anesthesiology, Yale University School of Medicine, New Haven, Connecticut, United States of America.
authors.forename: Steven G
authors.initials: SG
authors.lastname: Shimada
authors.affiliation: Department of Anesthesiology, Yale University School of Medicine, New Haven, Connecticut, United States of America; Department of Neurosurgery, Neurosurgery Pain Research Institute, Johns Hopkins University, Baltimore, Maryland.
authors.forename: Lintao
authors.initials: L
authors.lastname: Qu
authors.affiliation: Department of Anesthesiology, Yale University School of Medicine, New Haven, Connecticut, United States of America.
authors.forename: Kai
authors.initials: K
authors.lastname: Fu
authors.affiliation: Department of Anesthesiology, Yale University School of Medicine, New Haven, Connecticut, United States of America.
authors.forename: Pu
authors.initials: P
authors.lastname: Zhang
authors.affiliation: Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, School of Basic Medicine, Peking Union Medical College, Neuroscience Center, Department of Anatomy, Histology and Embryology, Beijing, China; Department of Anesthesiology, Yale University School of Medicine, New Haven, Connecticut, United States of America.
authors.forename: Chao
authors.initials: C
authors.lastname: Ma
authors.affiliation: Department of Anesthesiology, Yale University School of Medicine, New Haven, Connecticut, United States of America.
authors.forename: Robert H
authors.initials: RH
authors.lastname: LaMotte
mesh_terms: D000200:Action Potentials; D000818:Animals; D002908:Chronic Disease; D005727:Ganglia, Spinal / Q000503:physiopathology*; D006930:Hyperalgesia / Q000150:complications / Q000503:physiopathology; D008297:Male; D008810:Mice, Inbred C57BL; D009408:Nerve Compression Syndromes / Q000503:physiopathology*; D009619:Nociceptors / Q000378:metabolism*; D010146:Pain / Q000150:complications / Q000503:physiopathology*