Electroacupuncture Attenuates Neuropathic Pain in a Rat Model of Cervical Spondylotic Radiculopathy: Involvement of Spinal Cord Synaptic Plasticity

Abstract

Purpose Cervical spondylotic radiculopathy (CSR) is a common neurologic condition that causes chronic neck pain and motor functions, with neuropathic pain (NP) being the primary symptom. Although it has been established that electroacupuncture (EA) can yield an analgesic effect in clinics and synaptic plasticity plays a critical role in the development and maintenance of NP, the underlying mechanisms have not been fully elucidated. In this study, we explored the potential mechanisms underlying EA’s effect on synaptic plasticity in CSR rat models. Materials and Methods The CSR rat model was established by spinal cord compression (SCC). Electroacupuncture stimulation was applied to LI4 ( Hegu ) and LR3 ( Taichong ) acupoints for 20 min once a day for 7 days. Pressure pain threshold (PPT) and mechanical pain threshold (MPT) were utilized to detect the pain response of rats. A gait score was used to evaluate the motor function of rats. Enzyme-linked immunosorbent assay (ELISA), Western blot (WB), immunohistochemistry (IHC), immunofluorescence (IF), and transmission electron microscopy (TEM) were performed to investigate the effects of EA. Results Our results showed that EA alleviated SCC-induced spontaneous pain and gait disturbance. ELISA showed that EA could decrease the concentration of pain mediators in the cervical nerve root. WB, IHC, and IF results showed that EA could downregulate the expression of synaptic proteins in spinal cord tissues and promote synaptic plasticity. TEM revealed that the EA could reverse the synaptic ultrastructural changes induced by CSR. Conclusion Our findings reveal that EA can inhibit SCC-induced NP by modulating the synaptic plasticity in the spinal cord and provide the foothold for the clinical treatment of CSR with EA.

Acupuncture for radicular pain: a review of analgesic mechanism

“…It’s established that chronic pain can stem from the increased sensitivity of peripheral nociceptors in the spinal cord, coupled with persistent synaptic plasticity, highlighting the central role of synaptic changes in pain perception ( Bliss et al, 2016 ). Research by Yang P. et al (2023) in a rat model has demonstrated that electroacupuncture (EA) can mitigate the spinal cord compression (SCC)-induced upregulation of synaptic proteins, including α, 1, and 2, post-synaptic density protein 95 (PSD-95), and growth-associated protein 43 (GAP-43) within the spinal cord, suggesting EA’s capability to alter synaptic ultrastructure affected by CSR, thereby influencing the synaptic structure and functional plasticity to exert analgesic effects. Moreover, a study by Su J. et al (2023) revealed that EA effectively decreases the expression of pain-associated factor c-fos and the post-synaptic membrane protein neurontin 2 by inhibiting the expression of brain-derived neurotrophic factor (BDNF), phosphorylated tyrosine kinase B (P-TrkB), calmodulin-dependent protein kinase II (CAMKII), and phosphorylated response element binding protein (P-CREB) at spinal cord synapses.…”