Objective To observe the effect of repeated electroacupuncture(EA) on the expression of cannabinoid receptor-1(CB 1) mRNA and dopamine 1 receptor(D 1) mRNA in Nucleus Accumbens(NAC)-Caudate Nucleus(CN) region in inflammatory-pain rats

so as to study its underlying mechanism in analgesia.Methods A total of 30 SD rats were randomized into normal control

model

EA

EA+AM 251 and WIN 55212-2 groups

with 6 cases in each group.EA(2 Hz/100 Hz

1-3 mA) was applied to "Zusanli"(ST 36) and "Kunlun"(BL 60) for 30 min

once every other day

and 4 sessions all together.Arthritis model was established by injection of Freund's complete adjuvant 0.05 mL in the rat's left ankle.Thermal pain threshold(paw withdrawal latency

PWL) was detected before and after modeling and after repeated EA and/or intraperitoneal injection of AM 251(an inverse antagonist at the CB 1 cannabinoid receptor

0.1 mg/100 g) and WIN 55212-2(a potent cannabinoid receptor agonist

0.2 mg/100 g).The expression of CB 1 receptor mRNA and D 1 receptor mRNA in the NAC-CN region was measured by real time fluorescence quantitative-polymerase chain reaction.Results Compared with the control group

the pain threshold values of the model group was decreased significantly(P<0.01).In comparison with the model group

the pain threshold values of the EA group and WIN 55212-2 group were increased considerably on day 10(P<0.01).No significant differences were found between the EA+AM 251 and model groups and between the EA and WIN 55212-2 groups in PWL after the treatment(P>0.05).Compared with the control group

both CB 1 R mRNA and D 1 R mRNA expression levels in the model group were increased slightly

while in comparison with the model group and EA+AM 251 group

CB 1 R mRNA and D 1 R mRNA expression levels in the EA group and WIN 55212-2 group were upregulated obviously.No significant differences were found between the EA+AM 251 and model groups and between the EA and WIN 55212-2 groups in CB 1 R mRNA and D 1 R mRNA expression levels.