Loss of spinal μ-opioid receptor is associated with mechanical allodynia in a rat model of peripheral neuropathy

Seung Keun Back, Jaehee Lee, Seung Kil Hong, Heung Sik Na

Research output: Contribution to journalArticle

29 Citations (Scopus)

Abstract

The present study investigated whether the loss of spinal μ-opioid receptors following peripheral nerve injury is related to mechanical allodynia. We compared the quantity of spinal μ-opioid receptor and the effect of its antagonists, such as naloxone and CTOP, on pain behaviors in two groups of rats that showed extremely different severity of mechanical allodynia 2 weeks following partial injury of tail-innervating nerves. One group (allodynic group) exhibited robust signs of mechanical allodynia after the nerve injury, whereas the other group (non-allodynic group) showed little allodynia despite having suffered the same nerve injury. In addition, we investigated the quantity of spinal μ-opioid receptor and the effect of its antagonists on pain behaviors after the rats had recovered from mechanical allodynia 16 weeks following nerve injury. Immunohistochemical and Western blot analyses at 2 weeks after nerve injury indicated that spinal μ-opioid receptor content was more reduced in the allodynic group compared to the non-allodynic group. Intraperitoneal naloxone (2 mg/kg, i.p.) and intrathecal CTOP (10 μg/rat, i.t.) administration dramatically induced mechanical allodynia in the non-allodynic group. However, as in naïve animals, neither the loss of spinal μ-opioid receptors nor antagonist-induced mechanical allodynia was observed in the rats that had recovered from mechanical allodynia. These results suggest that the loss of spinal μ-opioid receptors following peripheral nerve injury is related to mechanical allodynia.

Original languageEnglish
Pages (from-to)117-126
Number of pages10
JournalPain
Volume123
Issue number1-2
DOIs
Publication statusPublished - 2006 Jul

Keywords

  • CTOP
  • Mechanical allodynia
  • Naloxone
  • Neuropathic pain
  • Peripheral nerve injury
  • Spinal μ-opioid receptor

ASJC Scopus subject areas

  • Neurology
  • Clinical Neurology
  • Anesthesiology and Pain Medicine

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