脊髓水平nNOS和iNOS在吗啡戒断反应中的作用差异

目的:观察鞘内注射选择性一氧化氮合酶(nNOS)和诱导型一氧化氮合酶(iNOS)抑制剂对吗啡依赖大鼠纳洛酮催促戒断反应、脊髓Fos蛋白表达和脊髓神经元nNOS和iNOS表达的影响,以探讨nNOS和iNOS在吗啡依赖和戒断反应中的作用。方法:在大鼠吗啡依赖和戒断模型上,采用行为学、免疫组织化学和Western blot方法观察鞘内应用nNOS抑制剂7-硝基吲哚(7-Ni)和iNOS抑制剂氨基胍(AG)对吗啡依赖大鼠纳洛酮催促戒断反应、脊髓Fos蛋白表达和脊髓神经元nNOS和iNOS表达的影响。结果:①鞘内注射7-Ni、AG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±4.89,7-Ni组为16.2±3.99(P<0.01),AG组为22.94±4.0(P<0.05);戒断组TEA评分为13.5±2.55,7-Ni、AG组分别为7.5±2.56、10.5±2.71(P<0.05);②鞘内注射7-Ni、AG可减少脊髓背角Fos阳性神经元的数目,7-Ni、AG组为228.2±49.5、296.8±50.6,低于戒断组(380±71,P<0.05);③7-Ni、AG组nNOS和iNOS阳性神经元的数目分别为169±32、10.2±2.85,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:nNOS和iNOS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nNOS和iNOS的表达,nNOS起主要作用而iNOS可能起辅助作用。

The different roles of the spinal protein nNOS and iNOS in morphine naloxone-precipitated withdrawal response

Objective: To explore the effects of intrathecal injection of neuronal nitric oxide synthase(nNOS) inhibitors 7-Nitroindazole(7-Ni) and inducible nitric oxide synthase(iNOS) inhibitors aminoguanidine(AG) on the behavioral changes of morphine-induced dependent and withdrawal rats;the expression of Fos,nNOS and iNOS in spinal cord.Methods: To set up morphine dependence model,rats were subcutaneously injected with morphine(twice a day,for 5 d).The dose of morphine was 10 mg/kg in the first day and was increased by 10 mg/kg every day.On day 6,4 h after the injection of morphine(50 mg/kg),morphine withdrawal syndrome was precipitated by an injection of nalo-xone(4 mg/kg ip).7-Ni,an nNOS inhibitor or iNOS inhibitors AG were intrathecally injected 30 min before the administration of naloxone respectively.The scores of morphine withdrawal symptom and morphine withdrawal-induced allodynia were observed.One hour after naloxonepecipitated withdrawal,Fos protein expression was assessed by immunohistochemical analysis and Western blot was used to detect the expression of nNOS and iNOS in the rat spinal cord.Results: Intrathecal administration of nNOS inhibitor 7-Ni and iNOS inhibitors AG decreased the scores of morphine withdrawal,attenuated morphine withdrawal-induced allodynia and also inhibited the increase of Fos protein expression in the spinal cord of morphine withdrawal rats.nNOS and iNOS positive neurons in dorsal horn in nNOS group and iNOS group were significantly lower than that in withdrawal group.Compared with withdrawal group,level of nNOS and iNOS protein in spinal cord in nNOS group and iNOS group were significantly lower.Conclusion: It is suggested that nNOS and iNOS in the spinal cord may contribute to naloxone-precipitated withdrawal in rats and may play different roles in the above-mentioned effect.