Objective To observe the effect of electroacupuncture(EA)on mechanical pain transition and content of protein kinase C epsilon(PKC_ε)in dorsal root ganglia(DRG)in inflammatory articular pain rats

so as to explore its peripheral mechanism underlying relieving transition from acute to chronic pain.Methods 1)In the first part of the present study

male SD rats were equally randomized into blank control

sham hyperalgesic priming(HP)

and real HP groups(n=6 in each).The HP model was established by subcutaneous injection of 1%carrageenan(100μL)into the left hind paw(the first injection)

followed by injection of PGE 2(100 ng/25μL

the second injection)into the dorsum pedis of the same hind paw 7 days after the first injection.The mechanical withdrawal threshold(MWT)of the ipsilateral paw was detected before and 4

24

48

72 h

and 7 dafter the first injection

and 1

4

24 and 48 hafter the second injection.2)In the second part

SD rats were randomly divided into sham-HP

real HP

sham-EA and EA groups(n=6 in each).The sham-HP and HP models were made in the same way as those in the first part.Bilateral"Zusanli"(ST 36)and "Kunlun"(BL 60)were punctured with filiform needles and also stimulated with electrical current:2 Hz/100 Hz

0.5-1.5 mA(0.5 mA increase per 10 min)for 30 min

1 time/d from the 1 st carrageenan injection on till the end of the experiments.PKC_εprotein expression in the L 4-L 6 DRGs was assayed by Western blot 48 hafter the second injection.Results 1)In the first part of the study

compared with the sham-HP group

the MWT at 4

24、48 hafter carrageenan injection and 4

24 and 48 h after PGE 2 injection were significantly decreased in the HP model group(P<0.01).2)In the second part

compared with the HP group

the MWT at 24、48 and 72 hafter carrageenan injection

and 24 and 48 hafter PGE 2 injection were significantly up-regulated in the EA group(P<0.05

P<0.01).3)The relative content of PKC_εin the DRGs(L 4-L 6)was significantly higher in the HP group than in the sham-HP group(P<0.01)

but considerably lower in the EA group than in the HP group(P<0.01). Conclusion EA has a good effect on pain conversion in inflammatory joint pain rats

which may be related to its effect in down-regulating the PKC_εlevel in the ipsilateral lumbar DRGs.