Distinct intensity of electroacupuncture ameliorates mechanical hypersensitivity by attenuating neuronal sensitization in spinal dorsal horn in a rat model of inflammatory muscle pain

Objective This study investigated the effects of distinct electroacupuncture (EA) intensities in alleviating mechanical hypersensitivity by attenuating spinal dorsal horn (SDH) neuronal sensitization in inflammatory muscle pain. Methods Male Sprague – Dawley rats received an intra-muscular injection of complete Freund’s adjuvant (CFA) in the left gastrocnemius muscle to induce inflammatory muscle pain. EA with distinct intensities activating Aβ-, Aδ- and C-fibers (EA Aβ , EA Aδ and EA C ) was applied after CFA injection. Pain behaviors were evaluated by weight-bearing asymmetry, the Randall–Selitto test, and the von Frey test. Spinal neuronal activities were observed by in vivo extracellular recordings with a microelectrode array. Neuronal sensitization was assessed through wind-up phenomenon of wide dynamic range (WDR) neurons and long-term potentiation (LTP) of spinal C-fiber-evoked field potential (CFEFP). Results Both EA Aδ and EA C significantly alleviated CFA-induced hyperalgesia. Moreover, EA Aδ and EA C interventions markedly reduced the activity of WDR neurons in response to stimulation. Importantly, the wind-up phenomenon of WDR neurons evoked by repetitive noxious stimuli was both immediately and sustainably reduced after EA intervention, with EA C showing a more pronounced effect. Furthermore, EA Aδ and EA C increased the threshold of the spinal CFEFP, while EA C intervention additionally significantly attenuated the occurrence of LTP. Conclusion Suppressing the SDH neuronal sensitization by activating Aδ- and C-fiber inputs may be the potential mechanism by which EA alleviates hyperalgesia in inflammatory muscle pain. Please cite this article as: Yu QQ, Sun XY, Chen JK, Li M, Wang XY, Su YS, Zhang ZY, Jing XH. Distinct intensity of electroacupuncture ameliorates mechanical hypersensitivity by attenuating neuronal sensitization in spinal dorsal horn in a rat model of inflammatory muscle pain. J Integr Med . 2026; 24(3):443–453.