Effect of Electroacupuncture on Thermal Pain Threshold and Expression of Calcitonin-Gene Related Peptide, Substance P and γ-Aminobutyric Acid in the Cervical Dorsal Root Ganglion of Rats with Incisional Neck Pain. Issue 4 (August 2017)

• Record Type: Journal Article
• Authors: Qiao, Li-na; Liu, Jun-ling; Tan, Lian-hong; Yang, Hai-long; Zhai, Xu; Yang, Yong-sheng
• Is Part Of: Acupuncture in medicine. Volume 35:Issue 4(2017)
• Page Start: 276
• Page End: 283
• Publication Date: 2017-08
• Subjects: Electroacupuncture -- Pain management -- COMPLEMENTARY MEDICINE -- PAIN RESEARCH -- WOUND MANAGEMENT; Acupuncture -- Periodicals; 615.892
• DOI: 10.1136/acupmed-2016-011177
• Languages: English
• ISSNs: 0964-5284

Abstract

Objective: Acupuncture therapy effectively reduces post-surgical pain, but its mechanism of action remains unclear. The aim of this study was to investigate whether expression of γ-aminobutyric acid (GABA) and the neuropeptides substance P (SP) and calcitonin gene-related peptide (CGRP) in the primary sensory neurons of cervical dorsal root ganglia (DRG) are involved in electroacupuncture (EA)-induced analgesia in a rat model of incisional neck pain. Methods: The pain model was established by making a longitudinal midline neck incision in 60 rats. Another 15 rats underwent sham surgery (normal group). Post-incision, 15 rats remained untreated (model group) and 45 rats underwent EA (frequency 2/100 Hz, intensity 1 mA) at bilateral LI18, LI4-PC6 or ST36-GB34 (n=15 each) for 30 min at 4 hours, 24 hours, and 48 hours post-surgery, followed by thermal pain threshold (PT) measurement. 30 min later, the rats were euthanased and cervical (C3-6) DRGs removed for measurement of immunoreactivity and mRNA expression of SP/CGRP and the GABAergic neuronal marker glutamic acid decarboxylase 67 (GAD67). Results: Thermal PT was significantly lower in the model group versus the normal group and increased in the LI18 and LI4-PC6 groups but not the ST36-GB34 group compared with the model group. Additionally, EA at LI18 and LI4-PC6 markedly suppressed neck incision-induced upregulation of mRNA/protein expression of SP/CGRP, and upregulated mRNA/protein expression of GAD67 in the DRGs of C3-6 segments. Conclusions: EA at LI18/LI4-PC6 increases PT in rats with incisional neck pain, which is likely related to downregulation of pronociceptive mediators SP/CGRP and upregulation of the inhibitory transmitter GABA in the primary sensory neurons of cervical DRGs.