水杨酸钠致耳鸣大鼠下丘GDNF的表达

Expression of GDNF in the Inferior Colliculus of Tinnitus RatsInduced by Sodium Salicylate

目的探究胶质细胞源性神经营养因子(glial cell-derived neurotrophic factor,GDNF)在慢性注射水杨酸钠致耳鸣大鼠模型下丘中的表达及其在耳鸣发生发展中的作用机制。方法将24只大鼠根据腹腔注射给药方式分为4组,每组6只:对照组(NS组,生理盐水连续注射14天)、急性组(AS组,水杨酸钠200 mg/kg单次注射)、慢性组(SS组,水杨酸钠200 mg/kg连续注射14天,每天2次)、恢复组(RS组,注射方式及时间同慢性组,然后正常喂养14天)。对各组大鼠经上述处理后行听觉惊跳反射前刺激抑制试验(gap-prepulse inhibition of the acoustic startle reflex,GPIAS)检测耳鸣样行为,然后处死并迅速分离下丘,通过蛋白质印迹法(Western blot)检测下丘GNDF及其信号通路RET、P-PI3K p85α、P-AKT蛋白表达量;通过荧光定量PCR(RT-qPCR)检测下丘GDNF、RET、PI3K、AKT1mRNA表达量。结果4组大鼠中仅SS组大鼠GPIAS值在12和16 kHz明显下降,说明仅SS组大鼠出现耳鸣样行为;Western blot结果显示SS组大鼠下丘GDNF、RET、P-PI3K p85α、P-AKT蛋白表达量较NS组、AS组、RS组均降低(均为P<0.05);RT-qPCR结果显示SS组大鼠下丘GDNF、RET、PI3K、AKT1mRNA表达量较NS组、AS组、RS组均降低(均为P<0.05)。结论慢性注射水杨酸钠致耳鸣大鼠模型下丘GDNF及其介导的GDNF/RET/PI3K/AKT信号通路表达降低,推测GDNF及其信号通路在耳鸣发生发展中有重要作用。

Objective To investigate the changes of expression of glial cell-derived neurotrophic factor(GDNF)in the inferior colliculus and its mechanism in the development of tinnitus in rats induced by chronic intraperitoned injection of sodium salicylate.Methods Twenty-four rats were randomly divided into four groups according to the method of intraperitoneal injection,six for each group:the control group(NS group,saline continuously injection for 14 days),acute injection group(As group,single injection of 200 mg/kg sodium salicylate),chronic injection group(SS group,200 mg/kg sodium salicylate continuously injection for 14 days)and recovery group(RS group,same sa SS group,but the rats were fed normally for another 14 days).The gap-prepulse inhibition of the acoustic startle reflex(GPIAS)was performed on the rats in each group after the above mentioned treatment,and the rats in each group were sacrificed and the inferior colliculus was rapidly isolated.The expressions of GNDF,RET,P-PI3K p85α,P-AKT in the inferior colliculus were detected by Western blot.The mRNA expressions of GDNF,RET,PI3K and AKT1 in the inferior colliculus were detected by fluorescence quantitative PCR(RT-qPCR).Results The GPIAS value of the SS group significantly decreased at 12kHz and 16kHz,indicating tinnitus behavior in the SS group.Western blot results showed that the expression levels of GDNF,RET,P-PI3K p85α,P-AKT in the inferior colliculus of the SS group were decreased compared with those of in the NS group,AS group and RS group.Rt-qPCR results showed that the expression levels of GDNF,RET,PI3K and AKT1 mRNA in the inferior colliculus of the SS group were decreased compared with those of in the NS group,AS group and RS group.Conclusion The expression of GDNF and its mediated GDNF/RET/PI3K/AKT signaling pathway were reduced in the inferior colliculus of tinnitus rats induced by chronic injection of sodium salicylate,suggesting that GDNF and its signaling pathway play an important role in the occurrence and development of tinnitus.