鞘内注射右美托咪啶对骨癌痛大鼠脊髓背角磷酸化cAMP反应元件结合蛋白表达的影响

Effect of intrathecal dexmedetomidine on expression of cAMP response element-binding protein phosphorylation in spinal dorsal horn in a rat model of bone cancer pain

目的探讨右美托咪啶对骨癌痛大鼠脊髓背角磷酸化cAMP反应元件结合蛋白（p—CREB）表达的影响。方法清洁级健康成年雌性Wistar大鼠64只，体重200—240g，采用随机数字表法，将其随机分为4组（n=16）：假手术组（S组）、骨癌痛组（BP组）、生理盐水组（NS组）和右美托咪啶组（D组）。BP组、NS组和D组采用胫骨骨髓腔注射10μl含Walker256乳癌细胞2×10^6个缓冲液的方法制备大鼠骨癌痛模型，S组和BP组不作鞘内注射，Ns组和D组于模型制备成功后7d分别鞘内注射生理盐水10出、右美托咪啶5μg／kg。分别于鞘内注射前1d（To）、注射前即刻（T1）、注射后1、6、12、24h（T1～5）时各组随机取10只大鼠，采用von Frey丝测定机械痛阈，各组余6只大鼠T4时处死取脊髓，采用免疫组化法测定脊髓背角p-CREB的表达。结果与S组比较，BP组、NS组和D组T1～5时机械痛阈降低，T4时脊髓背角p-CREB表达上调（P〈0．05）；与BP组比较，D组T2-5时机械痛阈升高，T4时脊髓背角p-CREB表达下调（P〈0．05），NS组机械痛阈和脊髓背角p-CREB表达差异无统计学意义（P〉0．05）。结论鞘内注射右美托咪啶可通过抑制大鼠脊髓背角CREB磷酸化减轻骨癌痛。

Objective To investigate the effect of intrathecal （IT） dexmedetomidine on the expression of cAMP response element-binding protein phosphorylation （p-CREB） in spinal dorsal horn in a rat model of bone cancer pain. Methods Sixty-four adult female Wistar rats weighing 200-240 g were randomly divided into 4 groups （n = 16 each）： sham operation group （group S）; bone cancer pain group （group BP）; normal saline group （group NS） ; dexmedetomidine group （group D）. Bone cancer pain was induced by injecting Walker 256 mammary gland carcinoma cell suspension （2 × 10^6 cells/ml） 10 μl into the medullary cavity of the tibia in BP, NS and D groups. Groups S and BP received no IT injection. Groups NS and D received IT injection of NS 10 μl and dexmedetomidine 5 μg/kg respectively 7 days after successful establishment of the model. Ten animals were selected from each group at 1 day before IT administration （T0）, immediately before IT administration （T1） and at 1, 6, 12 and 24 h after IT administration （T2-5） and paw withdrawal threshold （PWT） to mechanical stimuli was measured with yon Frey filaments. The other 6 rats in each group were sacrificed at T4 and the spinal cord was removed for determination of p-CREB expression in the spinal dorsal horn. Results PWT was significantly decreased at T1-5 and pCREB expression up-regulated at T4 in BP, NS and D groups compared with group S （P 〈 0.05）. Compared with group BP, PWT was significantly decreased at T2-5 and p-CREB expression down-regulated at T4 in group D （P 〈 0.05）, while no significant change in PWT and p-CREB expression was found in group NS （P 〉 0.05）. Conclusion IT dexmedetomidine can reduce the bone cancer pain through inhibiting the phosphorylation of CREB in rat spinal dorsal horn.