Pronociceptive actions of dynorphin maintain chronic neuropathic pain

Zaijie Wang, Luis R. Gardell, Michael H. Ossipov, Todd W. Vanderah, Miles B. Brennan, Ute Hochgeschwender, Victor J. Hruby, T. Phil Malan, Josephine Lai, Frank Porreca

Research output: Contribution to journalArticle

221 Scopus citations

Abstract

Whereas tissue injury increases spinal dynorphin expression, the functional relevance of this upregulation to persistent pain is unknown. Here, mice lacking the prodynorphin gene were studied for sensitivity to non-noxious and noxious stimuli, before and after induction of experimental neuropathic pain. Prodynorphin knock-out (KO) mice had normal responses to acute non-noxious stimuli and a mild increased sensitivity to some noxious stimuli. After spinal nerve ligation (SNL), both wild-type (WT) and KO mice demonstrated decreased thresholds to innocuous mechanical and to noxious thermal stimuli, indicating that dynorphin is not required for initiation of neuropathic pain. However, whereas neuropathic pain was sustained in WT mice, KO mice showed a return to baselines by post-SNL day 10. In WT mice, SNL upregulated lumbar dynorphin content on day 10, but not day 2, after injury. Intrathecal dynorphin antiserum reversed neuropathic pain in WT mice at post-SNL day 10 (when dynorphin was upregulated) but not on post-SNL day 2; intrathecal MK-801 reversed SNL-pain at both times. Opioid (μ, δ, and κ) receptor density and G-protein activation were not different between WT and KO mice and were unchanged by SNL injury. The observations suggest (1) an early, dynorphin-independent phase of neuropathic pain and a later dynorphin-dependent stage, (2) that upregulated spinal dynorphin is pronociceptive and required for the maintenance of persistent neuropathic pain, and (3) that processes required for the initiation and the maintenance of the neuropathic pain state are distinct. Identification of mechanisms that maintain neuropathic pain appears important for strategies to treat neuropathic pain.

Original languageEnglish (US)
Pages (from-to)1779-1786
Number of pages8
JournalJournal of Neuroscience
Volume21
Issue number5
DOIs
StatePublished - Mar 1 2001

Keywords

  • Dynorphin
  • Gene deletion
  • Gene knockout
  • Mouse
  • Neuropathic pain
  • Nociception
  • Opioid receptors
  • Prodynorphin
  • Spinal nerve injury
  • Transgenic

ASJC Scopus subject areas

  • Neuroscience(all)

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  • Cite this

    Wang, Z., Gardell, L. R., Ossipov, M. H., Vanderah, T. W., Brennan, M. B., Hochgeschwender, U., Hruby, V. J., Phil Malan, T., Lai, J., & Porreca, F. (2001). Pronociceptive actions of dynorphin maintain chronic neuropathic pain. Journal of Neuroscience, 21(5), 1779-1786. https://doi.org/10.1523/jneurosci.21-05-01779.2001