MEK抑制剂抑制吗啡依赖及戒断大鼠脊髓神经元NOS的表达

目的：观察鞘内注射丝裂原活化蛋白激酶抑制剂U0126对吗啡依赖及戒断大鼠戒断症状和痛敏行为以及脊髓神经元NOS表达的影响。方法：采用吗啡依赖及戒断模型,分为正常对照组、依赖组、戒断组（戒断1h）、U0126组,分别作行为学评分（n=8）、免疫组织化学（n=6）和免疫印迹检测（n=4）。结果：①鞘内注射U0126可明显减轻吗啡依赖大鼠戒断症状,戒断组戒断症状评分为28．6±4．89,U0126组为22．5±4．09（P〈0．05）;戒断组TEA评分为13．5±2．55,U0126组为10．0±2．76（P〈0．05）;②鞘内注射U0126可明显减少L5节段脊髓背角Fos阳性神经元的数目,U0126组为287±54,低于戒断组（380±71,P〈0．05）;③U0126组nNOS和iNOS阳性神经元的数目分别为180±32、10．8±2．8,均低于戒断组（239±45,16．8±5．1,P〈0．05）,两给药组脊髓NOS蛋白的表达也显著减少。结论：MEK抑制剂能减轻吗啡依赖及戒断大鼠的戒断症状和在脊髓水平抑制NOS的表达,表明ERK可能参与调控NOS的表达。

MEK inhibitors suppressed expression of NOS in spinal cord of morphine-induced dependent and withdrawal rats

Objective： To explore the effects of intrathecal injection of mitogen-activated protein kinases inhibitors U0126 on the behavioral changes of morphine-induced dependent and withdrawal rats and the expression of nitric oxide synthase （NOS） in spinal cord. Methods： All the rats were divided into 4 groups： control group, dependent group, withdrawal group, U0126 group （5 μg）. Global withdrawal score, Touch evoked agitation scores （TEA score）, immunohistochemical and Western blot technique were undertaken to evaluate behavioral changes and expression of FOS ,nNOS and iNOS in spinal cord respectively. Results： The results showed that intrathecal administration of U0126 significantly alleviated withdrawal symptom, withdrawal scores of U0126 group （22.5 ± 4.09） were significantly lower than than those of withdrawal group（28.6 ± 4.89） （ P 〈 0.05）. TEA scores of withdrawal group were 13.5 ± 2.55, which were significantly higher than those of U0126 group（10.0 ± 2.76, P 〈 0.05）. Fos-like positive neurons in dorsal horn of withdrawal group were 380 ± 71, which were higher than those of U0126 group（287 ± 54, P 〈 0.05） . Also nNOS and iNOS positive neurons in dorsal horn of U0126 group werel80 ± 32,10.8 ± 2.8 respectively, which were significantly lower than that of withdrawal group（239 ± 45, 16.8 ± 5.1, P 〈 0.05）. Compared with withdrawal group, levels of nNOS and iNOS protein in spinal cord of U0126 group were significantly lower. Conclusion： MEK inhibitors could alleviate withdrawal symptom of morphine-induced dependent rats and could suppress expression of NOS in spinal cord, and extracellular signal-regulate kinase（ERK）might involve the expression of NOS in spinal cord.