Objective To 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. Methods Fifty 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. Results In 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). Conclusion EA 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.