title: Role of sodium channels in recovery of sciatic nerve-stretch injury in rats.
abstract: BACKGROUND
  To elucidate the mechanism of functional recovery after gradual nerve-stretch injury, we used rats in which the femur length was increased by 15 mm at 1.5 mm/day.
  
  
  METHODS
  We performed electrophysiology, mRNA analysis of tetrodotoxin-resistant voltage-gated sodium channels (TTX-R VGSCs) in dorsal root ganglia, and histology of unmyelinated sciatic nerve fibers and examined pain thresholds at 1, 10, 20, and 30 days after cessation of lengthening.
  
  
  RESULTS
  Electrophysiology revealed conduction block after cessation that recovered after 30 days. TTX-R VGSC levels decreased immediately after cessation but were restored after 10 (Nav1.9) or 20 (Nav1.8) days. Histology revealed that injured unmyelinated nerve fibers regenerate 30 days after cessation. Pain threshold decreased gradually during lengthening but had not recovered to the control group level after 30 days.
  
  
  CONCLUSIONS
  Early restoration of TTX-R VGSC mRNA in dorsal root ganglia preceded functional recovery of stretched nerves before regeneration of injured unmyelinated nerve fibers.
authors.affiliation: Department of Orthopedic Surgery, Osaka Medical College, 2-7, Daigaku-machi, Takatsuki, Osaka, 569-8686, Japan.
authors.forename: Shinji
authors.initials: S
authors.lastname: Hirofuji
authors.forename: Atsushi
authors.initials: A
authors.lastname: Yokota
authors.forename: Katsunori
authors.initials: K
authors.lastname: Ohno
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Kinoshita
authors.forename: Masashi
authors.initials: M
authors.lastname: Neo
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D055724:Electrophysiological Phenomena; D005269:Femur / Q000502:physiology; D008854:Microscopy, Electron; D036421:Nerve Fibers, Unmyelinated / Q000473:pathology / Q000648:ultrastructure; D059225:Nociception / Q000502:physiology; D010812:Physical Stimulation; D051381:Rats; D017207:Rats, Sprague-Dawley; D060888:Real-Time Polymerase Chain Reaction; D012584:Sciatic Nerve / Q000293:injuries* / Q000473:pathology; D020426:Sciatic Neuropathy / Q000473:pathology; D015222:Sodium Channels / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology
chemical_list: D015222:Sodium Channels
keywords: dorsal root ganglion; limb lengthening; nerve elongation; peripheral nerve; sodium channels