• Cheng Ma, Cui-xian Li, Jian-liang Yi, and Li-ping Yan.
• Jiangsu Province Key Laboratory of Acu-moxibustion, Nanjing University of Chinese Medicine, Nanjing 210029, China. cma@njutcm.edu.cn
• Zhen Ci Yan Jiu. 2008 Aug 1;33(4):250-4.

ObjectiveTo observe the effect of electroacupuncture (EA) on pain threshold and contents of excitatory amino acids (EAA) in dorsal root ganglia (DRG) and spinal cord in rats with neuropathic pain.MethodsFifty SD rats were randomly divided into control (C),model (M), sham-model (SM), EA, and sham-EA groups, with 10 cases in each. Neuropathic pain (spared nerve injury, SNI) model was established by cutting off the right common peroneal nerve and proso-tibial nerve (with the sural nerve reserved intact). Before and after surgery, the mechanical pain threshold (MPT) and thermal pain threshold (TPT) were measured respectively on the injured side under consciousness state. EA (2 Hz, 1-3 mA, adding 1 mA/10 min) was applied to "Huantiao" (GB 30) and "Weizhong" (BL 40) on the affected side for 30 min. For rats of sham-EA group, filiform needles were inserted into GB30 and BL40 simply without manipulation or electrical stimulation. The treatment was given once daily for 7 days. On the 15th day, the rats were sacrificed for sampling right L4-L6 DRG and spinal cord. The contents of neurotransmitters, glutamate (Glu) and aspartic acid (Asp) in DRG and spinal cord were detected with high performance liquid chromatography (HPLC). Micro-dialysis technique was used to collect the dialysate from the spinal cord, homogenated for measuring EAA by HPLC.ResultsIn comparison with control group, after SNI, MPT decreased significantly from the 1st day on in model group. Compared with model group, on the 15th day, MPT increased significantly in both EA and sham-EA groups (P < 0.05, 0.01),but MPT of sham-EA was significantly lower than that of EA group (P < 0.05). No significant changes were found in TPT in 5 groups (P > 0.05). It suggested that sham EA still had an analgesic effect in spite of being lower than that of true EA. Compared with control group, the contents of Glu and Asp in the spinal cord tissue and micro-dialysate in model group increased significantly after SNI (P < 0.01). In comparison with model group, the contents of Glu in DRG and spinal cord tissue and micro-dialysate, and Asp in the spinal cord tissue and micro-dialysate in both sham-EA and EA groups decreased considerably (P < 0.05, 0.01). Dialysate Glu and spinal cord tissue Asp contents in EA were remarkably lower than those in sham-EA group (P < 0.01, 0.05).ConclusionEA has a significant analgesic effect in SNI rats, which is closely related with its effect in inhibiting the release of Glu and Asp from dorsal horns of the spinal cord and lowering contents of EAAs.

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