Electroacupuncture reduces chronic fibromyalgia pain through attenuation of transient receptor potential vanilloid 1 signaling pathway in mouse brains

Objective(s): Fibromyalgia pain is a mysterious clinical pain syndrome, characterized by inflammation in the brain, whose molecular mechanisms are still unknown. Females are more commonly affected by fibromyalgia, exhibiting symptoms such as widespread mechanical pain, immune dysfunction, sleep disturbances, and poor quality of life. Electroacupuncture (EA) has been used to relieve several types of pain, including fibromyalgia pain. Materials and Methods: In the present study, we used dual injections of acidic saline into the gastrocnemius muscle to initiate a neural activation that resulted in fibromyalgia pain in mice. We used the Von Frey test to measure mechanical hyperalgesia and Western blot to measure protein levels. Results: Results indicated that mechanical hyperalgesia can be induced in mice for 4 weeks, suggesting the induction of chronic fibromyalgia (CFM). Furthermore, continuous EA treatment reliably attenuated the mechanical hyperalgesia, but not in the sham control group. Results also suggested that the mechanical hyperalgesia can be prevented in mice with TRPV1 gene deletion. Mice with CFM showed increased expressions of TRPV1, Nav1.7, and Nav1.8 in the dorsal root ganglion (DRG) and the spinal cord (SC). The expression of TRPV1-associated molecules such as pPKA, pERK, and pCREB was also increased in the thalamus and somatosensory cortex (SSC) of the mice. All the aforementioned mechanisms were reversed by EA treatment and TRPV1 gene deletion. Conclusion: Altogether, our results implied significant mechanisms of CFM and EA-analgesia that involve the regulation of the TRPV1 signaling pathway. These findings may be relevant to the evaluation and treatment of CFM.