Downregulation of Spinal G Protein-Coupled Kinase 2 Abolished the Antiallodynic Effect of Electroacupuncture.

Huan Liu,Huijing Wang,Yan-Qing Wang,Qian Li,Shen-Bin Liu,Qi-Liang Mao-Ying

doi:10.1155/2015/848603

Huan Liu, Huijing Wang + Show 4 more

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https://doi.org/10.1155/2015/848603

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Abstract

Acupuncture or electroacupuncture (EA) has been demonstrated to have a powerful antihypernociceptive effect on inflammatory pain. The attenuation of G protein-coupled receptor kinase 2 (GRK2) in spinal cord and peripheral nociceptor has been widely acknowledged to promote the transition from acute to chronic pain and to facilitate the nociceptive progress. This study was designed to investigate the possible role of spinal GRK2 in EA antiallodynic in a rat model with complete Freund's adjuvant (CFA) induced inflammatory pain. EA was applied to ST36 (“Zusanli”) and BL60 (“Kunlun”) one day after CFA injection. Single EA treatment at day 1 after CFA injection remarkably alleviated CFA induced mechanical allodynia two hours after EA. Repeated EA displayed significant antiallodynic effect from 2nd EA treatment and a persistent effect was observed during the rest of treatments. However, downregulation of spinal GRK2 by intrathecal exposure of GRK2 antisense 30 mins after EA treatment completely eliminated both the transient and persistent antiallodynic effect by EA treatment. These pieces of data demonstrated that the spinal GRK2 played an important role in EA antiallodynia on inflammatory pain.

Highlights

Patients diagnosed with trauma, inflammatory diseases, cancer, and diabetes often suffer from persistent pain
EA treatment inhibited the activation of microglial p38 mitogen-activated protein kinase (p38MAPK) and extracellular signal-regulated kinase (ERK) signaling and attenuated the neuropathic pain caused by spinal cord injury [6]
complete Freund’s adjuvant (CFA) i.pl. injection provoked a significant reduction in paw withdrawal threshold (PWT) one day after injection (Figure 2(a)), and PWT sustained in a low level in the following 5 days (Figure 2(b))

Summary

Introduction

Inflammatory diseases, cancer, and diabetes often suffer from persistent pain. Acupuncture originated in ancient China has been proved to have a promising analgesic effect on several pain disorders, such as neuropathic pain, inflammatory pain, and cancer pain [1,2,3]. Electroacupuncture (EA), an important form of acupuncture, has been demonstrated to have an antiarthritic pain effect in monoarthritis rats by suppressing the proliferation of spinal microglia and decreasing the production of the proinflammatory cytokines including tumor necrosis factor- (TNF-) α, interleukin- (IL-) 1β, and IL-6 [4, 5]. EA treatment inhibited the activation of microglial p38 mitogen-activated protein kinase (p38MAPK) and extracellular signal-regulated kinase (ERK) signaling and attenuated the neuropathic pain caused by spinal cord injury [6].

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