KCC2-GABAA pathway correlates with the analgesic effect of electro-acupuncture in CCI rats

Potassium-chloride cotransporter 2 (KCC2) has been indicated to serve a crucial role during chronic neuropathic pain (NP). Following the emergence of NP, gamma-aminobutyric acid (GABA) A receptor-mediated signaling may be further impaired by the changes of KCC2 chloride anion gradient. In the present study, the authors investigate the effect of electro-acupuncture (EA) on the behavior and the expression of KCC2 and GABAA receptor gamma(2) subunit in the spinal cord of chronic constriction injury (CCI) model rats. A total of 60 adult male Sprague-Dawley rats were divided into four groups: Normal group, sham-CCI group, CCI group and CCI+EA group. The effect of EA was assessed via the values of mechanical withdrawal threshold and thermal withdrawal latency, which were significantly improved upon stimulation of the ST-36 and GB-34 acupoints. In addition, a marked reduction in both the mRNA and protein levels of KCC2 and GABAA receptor gamma(2) subunit was observed in the spinal cord following loose ligation of the sciatic nerve. The reductions in KCC2 and GABAA receptor gamma(2) subunit expression were reversed by EA treatment. These results support the notion that KCC2 and GABAA receptor gamma(2) subunit contribute to NP following peripheral nerve injury and extend the understanding of the analgesic effects of EA on NP.