急性和慢性吗啡依赖小鼠脑和脊髓20S蛋白酶体活性的变化

摘要

目的 探讨急性和慢性吗啡依赖小鼠脑和脊髓20S蛋白酶体活性的变化.方法 雄性ICR小鼠32只,体重25～ 30 g.实验Ⅰ 取小鼠16只,采用随机数字表法分为2组(n=8):对照组(C组)、急性吗啡依赖组(AMD组).实验Ⅱ 取小鼠16只,采用随机数字表法分为2组(n=8):对照组(C组)、慢性吗啡依赖组(CMD组).急性吗啡依赖模型:皮下注射吗啡100 mg/kg,3h后断头处死.慢性吗啡依赖模型:皮下注射吗啡,共4d,剂量依次为20、30、40、50 mg/kg,每日2次(8:00/20:00),第5天(8:00)皮下注射吗啡10 mg/kg,1h后断头处死.C组用等量生理盐水替代吗啡,其余处理同吗啡依赖组.小鼠断头处死后,分别取海马、前额皮层、纹状体和脊髓组织,采用荧光底物测定法分别检测20S蛋白酶体的糜蛋白酶样(ChT-L)、胰蛋白酶样(T-L)和多肽谷氨酰-多肽水解(PGPH)活性.结果 实验Ⅰ 与C组比较,AMD组脊髓20S蛋白酶体PGPH活性减弱,纹状体和前额皮层20S蛋白酶体T-L活性减弱(P＜0.05或0.01);2组海马20S蛋白酶体活性比较差异无统计学意义(P＞0.05).实验Ⅱ 与C组比较,CMD组脊髓20S蛋白酶体ChT-L和T-L活性减弱,纹状体20S蛋白酶体PGPH活性增强(P＜0.05或0.01);2组前额皮层及海马20S蛋白酶体活性比较差异无统计学意义(P＞0.05).结论 急性吗啡依赖小鼠脊髓和脑组织20S蛋白酶体活性减弱,慢性吗啡依赖小鼠脊髓20S蛋白酶体活性减弱,纹状体蛋白酶体活性增强,均具有部位和活性类型特异性,以上改变可能与小鼠吗啡依赖的形成有关.%Objective To investigate the changes in 20S proteasome activities in the brain and spinal cord of acute and chronic morphine-dependent mice.Metbods Male ICR mice,weighing 25-30 g,were used in the study.The experiment was performed in 2 parts.In experiment Ⅰ,16 mice were randomly divided into 5 groups (n =8 each) using a random number table:control group (group C) and acute morphine dependence group (AMD group).In experiment Ⅱ,16 mice were randomly divided into 5 groups (n =8 each) using a random number table:control group (group C) and chronic morphine dependence group (CMD group).Acute morphine dependence was induced with morphine 100 mg/kg injected subcutaneously,and the mice were sacrificed 3 h later.Chronic morphine dependence was induced by increasing doses of morphine for 4 days,the initial dose of morphine was 20 mg/kg injected subcutaneously twice a day and was increased by 10 mg/kg every day,the dose of morphine was 10 mg/kg injected subcutaneously on 5th day,and then the mice were sacrificed 1 h later.In group C,the equal volume of normal saline was given instead,and the other treatments were similar to those previously described in morphine dependence groups.After the mice were sacrificed,the hippocampus,prefrontal cortex,striatum and spinalcord were isolated for determination of 20S proteasome activity,measured as chymotrypsin-like (ChT-L),trypsin-like (T-L) and peptidylglutamyl-like hydrolyzing (PGLH) activities.Results Experiment Ⅰ Compared with C group,PGLH activity in the spinal cord and T-L activity in the striatum or prefrontal cortex were significantly weakened in group AMD.There was no significant difference in 20S proteasome activity in the hippocampus between the two groups.Experiment Ⅱ Compared with C group,ChT-L and T-L activities in the spinal cord were significantly weakened,and PGLH activity in the striatum was enhanced in CMD group.There was no significant difference in 20S proteasome activity in the prefrontal cortex and hippocampus between the two groups.Conclusion 20S proteasome activity in the spinal cord and brain is weakened in acute morphine-dependent mice,20S proteasome activity in the spinal cord is weakened,20S proteasome activity in the striatum is enhanced in chronic morphine-dependent mice,these changes have specificity in terms of position and type of activity,and the changes mentioned above may be related to development of morphine dependence in mice.