脊髓背角趋化因子受体CXCR4在骨癌痛大鼠吗啡耐受形成中的作用

Role of chemokine receptor CXCR4 in spinal dorsal horn in development of morphine tolerance in rats with bone cancer pain

目的 评价脊髓背角趋化因子受体CXCR4在骨癌痛大鼠吗啡耐受形成中的作用.方法 清洁级健康成年雌性SD大鼠40只,体重180～220 g,采用随机数字表法分为5组（n=8）：假手术组（S组）、骨癌痛组（B组）、骨癌痛＋ CXCR4特异性拮抗剂AMD3100组（BA组）、骨癌痛＋吗啡组（BM组）和骨癌痛＋吗啡＋ AMD3100组（BMA组）.B组右侧胫骨骨髓腔注射Walker 256乳腺癌细胞5μ1（4×105个/ml）；于注射乳腺癌细胞后第6天,BA组腹腔注射AMD3100 2 mg/kg,2次/d,连续9d,BM组皮下注射吗啡10 mg/kg,2次/d,连续9 d;BMA组腹腔注射AMD3100（同BA组）,皮下注射吗啡（同BM组）.于乳腺癌细胞注射前（T0）、注射后4、6、8、10、12和14 d（T1-6）时测定机械痛阈,随后处死大鼠取L3-5脊髓背角,采用免疫荧光法检测c-fos的表达.结果 与S组比较,B组和BA组T2-6时、BM组T4-6时机械痛阈降低,T6时脊髓背角c-fos表达上调（P＜0.01）；与B组比较,BM组T3-5时和BMA组T3-6时机械痛阈升高（P＜0.01）；与BM组比较,BMA组T5,6时机械痛阈升高,T6时脊髓背角c-fos表达下调（P＜0.01）.结论 脊髓背角趋化因子CXCR4受体参与了骨癌痛大鼠吗啡耐受的形成,其机制可能与c-fos活化有关.

Objective To evaluate the role of chemokine receptor CXCR4 in spinal dorsal horn in the development of morphine tolerance in rats with bone cancer pain （BCP）.Methods Forty female Sprague-Dawley rats,weighing 180-220 g,were equally randomized into 5 groups using a random number table：sham operation group （group S）,BCP group （group B）,BCP ＋ AMD3100 （specific CXCR4 antagonist） group （group BA）,BCP ＋ morphine group （group BM）,BCP ＋ morphine ＋ AMD3100 group （group BMA）.BCP was induced by injecting Walker 256 mammary gland cancer cell suspension （4 × 105 cells/ml） 5 μl into the bone marrow of the right tibia of rats anesthetized with chloral hydrate.On 6 days after injection of mammary gland cancer cells,AMD3100 2 mg/kg was intraperitoneally injected twice a day for 9 days in BA group,and morphine 10 mg/kg was subcutaneously injected twice a day for 9 days in BM group.AMD3100 was intraperitoneally injected and morphine was subcutaneously injected as previously described at the corresponding time point in BMA group.Before injection of mammary gland cancer cells （T0） and on 4,6,8,10,12 and 14 days after injection of mammary gland cancer cells （T1-6）,paw withdrawal threshold to von Frey hair mechanical stimulation （PWMT） was measured.The rats were then sacrificed and L3-5 segments of the spinal cord were removed for determination of c-fos expression in spinal dorsal horn using immunofluorescence.Results Compared with S group,PMWT was significantly decreased at T2-6 in B and BA groups and at T4-6 in BM group,and c-fos expression was up-regulated at T6 in BM group （P 〈0.01）.PMWT was significantly higher at T3-5 in BM group and at T3-6 in BMA group than in group B （P 〈 0.01）.Compared with BM group,PMWT was significantly increased at T5,6 and c-fos expression was down-regulated at T6 in BMA group （P 〈 0.01）.Conclusion Chemokine receptor CXCR4 in spinal dorsal horn is involved in the development of morphine tolerance in rats with BCP and the mechanism may be related to activation of c-fos.