水杨酸盐诱发大鼠听皮层中Egr-1基因表达的改变

摘要

Objective To investigate the centrol mechanisms in tinnitus by observation of the auditory cortex plastic changes in a tinnitus animal model. Methods Kighty- four healthy 8 weeks old male SD rats were randomly divided into seven groups; Group A(control group) , Group B(acute salicylate injections within 2 hours) , Group C (chronic salicylate injections with 3 days) ,Group D(chronic salicylate injections for 7 days) , Group E(chronic salicylate injections for 14 days), Group F(chronic injections with recovery 14 days) and Group G(chronic injections with recovery 28 days). The rats were sacrified at different time points as above and the rat auditory cortex tissue were obtained. SYBR Green real-time reverse transcriptase polymerase chain reaction (real-time RT - PCR) and Western blot were used to study the different expression of early growth response protein-l(Egr-1) mRNA and protein levels in these seven groups. Results As compared with that of control group, the expression of Egr-1 mRNA and protein level in these three groups(Group C, Group D and Group E) were significantly decreased (P< 0. 05). There were no significant changes among the control group , Group B , Group F and Group G(P>0. 05). Conclusion Chronic salicylate administration markedly, but reversibly, decreased the expression of Egr-1 mRNA and protein levels in rat aduitory cortex indicating that plastic changes in auditory cortex neurons and its possible role of central mechanisms in tinnitus.%目的 通过观察慢性水杨酸盐诱导的大鼠耳鸣模型听皮层早期生长反应基因-1(early growth response gene-1,Egr-1)的表达,了解其是否出现皮层中枢可塑性的变化,探讨耳鸣产生的中枢机制.方法将84只8周龄SPF级健康雄性SD大鼠按水杨酸盐的给药时间随机分为7组,分别为:正常对照组、急性注射2小时组、慢性注射3天组、慢性注射7天组、慢性注射14天组、停药后恢复14天组、停药后恢复28天组.在完成急、慢性水杨酸肌肉注射成功建立大鼠耳鸣动物模型后,于上述各时间点将各组大鼠断头处死后迅速分离出听皮层,采用SYBR Green实时荧光定量PCR(real-time reverse transcriptase polymerase chain reaction,real-time RT-PCR)及Western blot(蛋白质印迹)方法,检测各组大鼠听皮层Egr-1 mRNA及其蛋白的表达,比较各组间的差异.结果慢性注射3天组、慢性注射7天组、慢性注射14天组大鼠听皮层的Egr-1 mRNA 及其蛋白表达水平较正常对照组低,差异有统计学意义(P＜0.05);急性注射2小时组、停药后恢复14天组、停药后恢复28天组大鼠听皮层Egr-1 mRNA 及其蛋白表达水平与正常对照组无明显差异(P>0.05).结论 长期注射水杨酸盐导致耳鸣的大鼠听皮层中与中枢可塑性密切相关的Egr-1基因表达可逆性下调,表明听皮层神经元发生了可塑性改变,推测听皮层神经元可塑性改变可能参与了耳鸣的形成和发展.