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

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.

• Authors: Seu-Hwa Chen, June-Horng Lue, Yung-Jung Hsiao, Shu-Mei Lai, Hsin-Ying Wang, Chi-Te Lin, Ya-Chin Chen, Yi-Ju Tsai
• Journal: PloS one (PLoS One) Vol. 13 Issue 6 Pg. e0199512 ( 2018) ISSN: 1932-6203 [Electronic] United States
• PMID: 29928003 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

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

Topics

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