Kilohertz High-Frequency Electrical Stimulation Effectively Mitigates Hyperalgesia in Mice With Neuropathic Pain Through Regulation of the Calcium/Calmodulin-Dependent Protein Kinase II/N-Methyl-D-Aspartate 2B Signaling Pathway.

Abstract

Objectives: Kilohertz high-frequency electrical stimulation (KHES), an avant-garde neuromodulation strategy, is progressively emerging in the field of neuropathic pain management, showing its unique therapeutic potential. This study delves into the mechanisms by which KHES exerts therapeutic effects on neuropathic pain induced by chronic constriction injury (CCI) in mice through modulation of the calcium/calmodulin-dependent protein kinase II (CaMKII)/N-methyl-D-aspartate receptor 2B (NMDAR2B) signaling pathway.

Materials and methods: In this study, mice were randomly assigned to groups and received intrathecal injections of CaMKII activator BayK8644, CaMKII inhibitor KN93, and N-methyl-D-aspartate (NMDA). Subsequently, mice underwent a week-long KHES treatment, with each session lasting 30 minutes. The impact of KHES on mechanical allodynia and thermal hyperalgesia in mice was assessed through paw withdrawal threshold and thermal withdrawal latency measurements, respectively. In addition, anxiety and depressive-like behaviors in mice were evaluated using pole climbing, open field, and forced swim tests. Quantitative reverse transcription polymerase chain reaction, Western blot, and immunofluorescence techniques were used to detect the expression levels of CaMKII, phosphorylated CaMKII (p-CaMKII), and NMDAR2B in the spinal cord.

Results: Results indicated that KHES not only significantly reduced mechanical allodynia in CCI mice, with a sustained analgesic effect lasting up to six hours, but also somewhat alleviated anxiety and depressive-like symptoms. KHES inhibited the expression of p-CaMKII and NMDAR2B in the spinal cord. This inhibitory effect was reversed in the presence of BayK8644 and NMDA, suggesting that activation of CaMKII and NMDAR2B may contribute to the maintenance of neuropathic pain. Conversely, KN93 enhanced the analgesic effect of KHES by reducing mechanical allodynia and downregulating p-CaMKII and NMDAR2B expression, further confirming the significance of the CaMKII/NMDAR2B signaling pathway in KHES-mediated neuropathic pain relief.

Conclusion: This study not only unveils the potential therapeutic value of KHES in treating neuropathic pain induced by CCI in mice but also provides insights into its molecular mechanisms of action through inhibition of the CaMKII/NMDAR2B signaling pathway.