Objective To observe the effect of electroacupuncture(EA)on expression of pain sensory and affective processing-relatedμ-opioid receptor(MOR)

glutamatergic AMPA receptor subunit GluA 1

extracellular signal-regulated kinase(ERK 1/2)

cAMP response element binding protein(CREB)in the amygdala in chronic constrictive injury(CCI)+ negative affection(NA)rats

so as to reveal its mechanism underlying pain relief.Methods A total of 32 male Wistar rats were randomized into normal control

model

EA

and anesthesia+EA(AEA)groups(n=8in each group).The neuropathic pain NA model was established by ligation of the left sciatic nerve and repeated electrical stimulation of the paw-bottom in the pain-paired compartment.EA was applied to bilateral"Zusanli"(ST 36)and"Yanglingquan"(GB 34)for 30 min

once daily for 7days.Thermal pain threshold(paw withdrawl latency

PWL)of the bilateral paws was measured by using a Tail-Flick Unit.The expression levels of MOR and p-CREB in the central amygdala(CeA)and those of MOR

GluA 1

p-ERK 1/2and p-CREB in the right amygdala area were determined using immunofluorescence and Western blot

respectively.Results In comparison with the normal group

PWL difference(PWLD)values of the model group were significantly increased(P<0.001)

and the time spent in the CPA-paired compartment was considerably decreased(P<0.001).After EA

the PWLD levels of both EA and AEA groups were apparently decreased(P<0.05)

showing apain relief;and the time spent in the CPA-paired compartment was apparently increased in the EA group(P<0.05)

rather than in the AEA group(P>0.05).Additionally

compared to the normal group

the expression level of MOR protein in the amygdala was remarkably increased(P<0.05)and those of GluA 1

p-ERK 2and p-CREB proteins were apparently decreased(P<0.05).After EA intervention for 7days

the expression levels of these four proteins in the EA group

and those of MOR

p-ERK 2and p-CREB in the AEA group were significantly up-regulated(P<0.001

P<0.01

P<0.05).The expressionlevel of GluA 1was significantly higher in the EA group than in the AEA group(P<0.05).Conclusion Repeated EA stimulation of ST 36-GB 34 has a definite effect in relieving both sensation and affection dimensions of pain in NA rats

which may be related to its effect in up-regulating the expression of GluA 1in the amygdala

but the effects of MOR

p-ERK 2and p-CREB need being researched further.