Elevated galanin receptor type 2 primarily contributes to mechanical hypersensitivity after median nerve injury

PLoS One. 2018 Jun 21;13(6):e0199512. doi: 10.1371/journal.pone.0199512. eCollection 2018.

Abstract

In this study, we investigated temporal changes in galanin receptor type 2 (GalR2) expression in NF200-, galanin-, neuropeptide Y (NPY)-, and neuronal nitric oxide synthase (nNOS)-like immunoreactive (LI) dorsal root ganglion (DRG) neurons after median nerve chronic constriction injury (CCI), and the effects of GalR2 on c-Fos expression in the cuneate nucleus (CN). Double immunofluorescence labeling methods were used to appraise changes in GalR2 expression in NF200-LI, galanin-LI, NPY-LI, and nNOS-LI DRG neurons after CCI. The von Frey assay was used to assess the efficiency of intraplantar administration of saline, M871 (a GalR2 antagonist), or AR-M1896 (a GalR2 agonist) on neuropathic signs of rats with CCI. The effects of alterations in c-Fos expression were assessed in all treatments. The percentage of GalR2-LI neurons in lesioned DRGs increased and peaked at 1 week after CCI. We further detected that percentages of GalR2-LI neurons labeled for NF200, galanin, NPY, and nNOS significantly increased following CCI. Furthermore, M871 remarkably attenuated tactile allodynia, but the sensation was slightly aggravated by AR-M1896 after CCI. Consequentially, after electrical stimulation of the CCI-treated median nerve, the number of c-Fos-LI neurons in the cuneate nucleus (CN) was significantly reduced in the M871 group, whereas it increased in the AR-M1896 group. These results suggest that activation of GalR2, probably through NPY or nitric oxide, induces c-Fos expression in the CN and transmits mechanical allodynia sensations to the thalamus.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Chronic Disease
  • Constriction, Pathologic
  • Galanin
  • Ganglia, Spinal / metabolism
  • Hyperalgesia / metabolism*
  • Hyperalgesia / pathology
  • Male
  • Median Nerve / injuries*
  • Median Nerve / metabolism*
  • Median Nerve / pathology
  • Nerve Tissue Proteins / metabolism
  • Neurons / metabolism
  • Rats, Sprague-Dawley
  • Receptor, Galanin, Type 2 / agonists
  • Receptor, Galanin, Type 2 / antagonists & inhibitors
  • Receptor, Galanin, Type 2 / metabolism*

Substances

  • Nerve Tissue Proteins
  • Receptor, Galanin, Type 2
  • Galanin

Grants and funding

This work was supported by NSC101-2320-B002-006 and NSC102-2320-B002-004-MY3, National Science Council (https://www.most.gov.tw/), JHL. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.