Objective] To investigate whether the mechanism of electro-acupuncture(EA)-induced antinociception was related to intervention in spinal opioid peptide precursor mRNA in subcutaneous tumor model rats. [Methods] The female SD rats were randomly divided into four groups: sham-operation group, operation group, EA group, sham-EA group. Subcutaneous tumor-induced pain model was established by injecting subcutaneously 100μl Walker 256 breast cancer cells suspension(the cell concentration is 1 ×107cells/ml) into the right paw of the later three groups. Rats in the sham-operation groups were injected with the same amount of sterile PBS. One day after inoculation, EA was applied to bilateral "Zusanli"(ST36) and "Kunlun"(BL60) for 30min, once a day, and which had been lasted for 7 days. Rats in the sham-EA group were inserted by needles slightly which connected with Han's Acupoint Nerve Stimulator without electricity. The day before inoculation, and 1d, 2d, 4d, 8d after inoculation, TFL(Tail Flick Latency) had been dynamically observed. The expression of PDYN(prodynorphin, PDYN) and POMC (pro-opiomelanocortin, POMC)mRNA were observed by qPCR method. [Results] Before surgery, there were no statistical differences in TFL among four groups. One day after surgery, compared with sham-operation group, TFL of the operation group, EA group and sham-EA group had significantly decreased( P<0.01). After 1, 3, 5, 7 times of EA treatments, compared with the operation group and sham EA group, TFL of the EA group had significantly improved( P<0.01), and had no statistical difference with sham operation group(P>0.05). However, each point of time after EA treatment, TFL of the sham EA group was significantly lower than sham operation group( P<0.01), at the same time, TFL of the sham EA group had no statistical difference with operation group( P>0.05). Compared with three other groups, the expression of PDYN mRNA in ipsilateral dorsal horn of lumbar spinal cord of EA group was up-regulated, without statistical difference( P>0.05), and the expression of POMC mRNA was not significantly different(P>0.05). [Conclusion] EA has an obvious analgesic effect on cancer pain and its mechanism of immediate effect may not be related to up-regulating the expression of PDYN mRNA and POMC mRNA in ipsilateral spinal dorsal horn.%[目的]观察电针对皮下肿瘤致痛大鼠的镇痛效应及电针对癌痛大鼠腰段脊髓背角阿片肽前体mRNA表达的干预，初步探讨电针抗癌性痛的中枢阿片机制。[方法]雌性SD大鼠完全随机分为假手术组、手术组、电针治疗组和假电针治疗组，后3组以大鼠右侧足跖掌面皮下注射Walk－er256乳腺癌细胞悬液100μl（1×107cells/ml）建立大鼠皮下肿瘤癌痛模型，假手术组在同部位注入等量灭菌PBS。造模后1d电针治疗组介入电针治疗，连续治疗7d，而假电针组仅针刺破皮，连接电针仪但不通电。动态观察各组大鼠造模前（基础）、造模后1d、2d、4d、6d和8d甩尾潜伏期（Tail Flick latency, TFL）的变化。采用荧光定量PCR法检测腰段脊髓背角前强啡呔原（prodynorphin, PDYN）和阿黑皮素(pro-opiomelanocortin, POMC） mRNA的相对表达量。[结果]造模前各组大鼠TFL无统计学差异（P>0.05）；造模后1d手术组、电针治疗组、假电针组大鼠TFL明显低于假手术组（P<0.01）；电针治疗1、3、5、7次后即刻，电针治疗组大鼠TFL均显著高于手术组和假电针治疗组（P<0.05或P<0.01），且与假手术组比较差异无统计学意义（P>0.05）；治疗后各时间点，假电针组大鼠TFL始终显著低于假手术组（P<0.01），且与手术组大鼠比较差异无统计学意义（P>0.05）。与其余3组相比，电针治疗组大鼠患侧腰段脊髓背角PDYN mRNA表达呈上调趋势，但无统计学差异（P>0.05），POMC mRNA表达无显著差异（P>0.05）。[结论]电针对癌性痛有良好的即时镇痛效应，其机制可能与患侧脊髓背角PDYN mRNA及POMC mRNA表达量无关。
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