Evaluation of behavior and neuropeptide markers of pain in a simple, sciatic nerve-pinch pain model in rats

Eur Spine J. 2010 Oct;19(10):1746-52. doi: 10.1007/s00586-010-1428-4. Epub 2010 May 20.

Abstract

Pathomechanisms of injured-nerve pain have not been fully elucidated. Radicular pain and chronic constriction injury models have been established; however, producing these models is complicated. A sciatic nerve-pinch injury is easy to produce but the reliability of this model for evaluating pain behavior has not been examined. The current study evaluated pain-related behavior and change in pain markers in the dorsal root ganglion (DRG) of rats in a simple, sciatic nerve-pinch injury model. In the model, the sciatic nerve was pinched for 2 s using forceps (n = 20), but not injured in sham-operated animals (n = 20). Mechanical and thermal hyperalgesia were measured every second day for 2 weeks using von Frey filaments and a Hargreaves device. Calcitonin gene-related peptide (CGRP), activating transcription factor-3 (ATF-3), phosphorylated p38 mitogen activated protein (Map) kinase (p-p38), and nuclear factor-kappa B (NF-κB; p65) expression in L5 DRGs were examined at 4 and 7 days after surgery using immunohistochemistry. The proportion of neurons immunoreactive for these markers was compared between the two groups. Mechanical (during 8 days) and thermal hyperalgesia (during 6 days) were found in the pinch group rats, but not in the sham-operated animals (p < 0.05); however, hyperalgesia was not significant from days 10 to 14. CGRP, ATF-3, p-p38, and NF-κB expression in L5 DRGs was upregulated in the nerve-injured rats compared with the sham-operated rats (p < 0.01). Our results indicate that a simple sciatic nerve pinch produced pain-related behavior. Upregulation of the pain-marker expression in the nerve-injury model suggested it could be used as a model of pain. However, it was not considered as suitable for long-term studies.

MeSH terms

  • Animals
  • Behavior, Animal / physiology*
  • Biomarkers / metabolism
  • Disease Models, Animal
  • Male
  • Neuropeptides / metabolism*
  • Pain / diagnosis
  • Pain / metabolism*
  • Pain / physiopathology*
  • Pain Measurement / methods*
  • Rats
  • Rats, Sprague-Dawley
  • Sciatica / diagnosis
  • Sciatica / metabolism*
  • Sciatica / physiopathology*

Substances

  • Biomarkers
  • Neuropeptides