Time course of substance P expression in dorsal root ganglia following complete spinal nerve transection

J Comp Neurol. 2006 Jul 1;497(1):78-87. doi: 10.1002/cne.20981.


Recent evidence suggests that substance P (SP) is up-regulated in primary sensory neurons following axotomy and that this change occurs in larger neurons that do not usually produce SP. If this is so, then the up-regulation may allow normally neighboring, uninjured, and nonnociceptive dorsal root ganglion (DRG) neurons to become effective in activating pain pathways. By using immunohistochemistry, we performed a unilateral L5 spinal nerve transection on male Wistar rats and measured SP expression in ipsilateral L4 and L5 DRGs and contralateral L5 DRGs at 1-14 days postoperatively (dpo) and in control and sham-operated rats. In normal and sham-operated DRGs, SP was detectable almost exclusively in small neurons (< or =800 microm2). After surgery, the mean size of SP-positive neurons from the axotomized L5 ganglia was greater at 2, 4, 7, and 14 dpo. Among large neurons (>800 microm2) from the axotomized L5, the percentage of SP-positive neurons increased at 2, 4, 7, and 14 dpo. Among small neurons from the axotomized L5, the percentage of SP-positive neurons was increased at 1 and 3 dpo but was decreased at 7 and 14 dpo. Thus, SP expression is affected by axonal damage, and the time course of the expression is different between large and small DRG neurons. These data support a role for SP-producing, large DRG neurons in persistent sensory changes resulting from nerve injury.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Cell Count / methods
  • Functional Laterality / physiology
  • Ganglia, Spinal / metabolism*
  • Ganglia, Spinal / pathology
  • Gene Expression Regulation / physiology*
  • Immunohistochemistry / methods
  • Male
  • Neurons / classification
  • Neurons / metabolism
  • Rats
  • Rats, Wistar
  • Spinal Cord Injuries / metabolism*
  • Spinal Cord Injuries / physiopathology*
  • Substance P / metabolism*
  • Time Factors


  • Substance P