Objective: To observe the effects of electroacupuncture(EA) on hyperalgesia

inflammatory tissue repair and the expression of spinal COX-2 mRNA and protein in rats with chronic inflammatory pain.Methods: Chronic inflammatory pain model was established by injection of complete Freund's adjuvant(CFA) into the SD rat's left ankle-joint cavity of the hind limb.EA((2 Hz)

(1 mA)

continuous waves) was applied to "Yanglingquan"(GB 34) and "Kunlun"(BL 60) for(20 min)

once daily

continuously for(1 d)

(4 d)

(6 d)

(8 d) and(10 d) respectively.For observing changes of tissue repair of the focus

HE staining technique was used;and for determining the expression of spinal COX-2 mRNA and COX-2 protein in the dorsal horns of the lumbar spinal cord

immunohistochemical and RT-PCR techniques were carried out.Results: After 6 days' EA treatment

the hyperalgesic score of EA group(n=6) was significantly lower than that of model group(n=6);and after 8 and 10 days' treatment

the decreased hyperalgesic score of EA group was similar to that of control group(n=6

P>0.05).Compared with model 1((4 d) after injection of CFA

n=3) and 2((14 d) after injection of CFA

n=3)

the exudation of the joint cavity

synovium edema

and infiltration of mononuclear cells of EA group(n=6) were improved remarkably.In comparison with control group

4 days after injection of CFA

spinal COX-2 mRNA expression and COX-2 immuno-reaction positive cell number of model group increased significantly(P<0.05);6 days after EA

no significant differences were found between control and EA groups in both COX2 mRNA expression and COX-2 immuno-reaction positive cell number(P>0.05)

indicating that EA could down-regulate the expression of COX-2 mRNA and COX-2 protein in the spinal cord.Conclusion: EA has a remarkable analgesic effect and can promote the repair of inflammatory tissue

which may be related to its functions in down-regulating the expression of COX-2 mRNA and COX-2 protein in the spinal cord.