长期注射水杨酸钠对大鼠听皮层酪氨酸受体激酶B及c－fos基因表达的影响

摘要

目的：通过观察长期注射水杨酸钠后大鼠听皮层中酪氨酸受体激酶B（TrkB）及c－fos基因的表达，探讨其在水杨酸钠耳毒性机制中的作用。方法健康成年Wistar大鼠36只，分为正常组（不做任何处理）、慢性组（肌肉注射水杨酸钠175 mg／kg ，2次／天，时间间隔8小时，连续注射14天）、慢性恢复组（前期处理同慢性组，停药后恢复28天），每组12只。造模结束后各组大鼠均行听性脑干反应（ABR）检测，然后断头处死并迅速取出听皮层，运用实时荧光定量PCR技术及Western－blot技术分别检测三组大鼠听皮层中TrkB及c－fos的表达。结果正常组ABR反应阈为36±2．23 dB SPL ，慢性组反应阈升高为41．3±3．31 dB SPL ，与正常组比较，差异有显著统计学意义（P＜0．01）；慢性恢复组ABR反应阈为38．6±5．51 dB SPL ，与正常组比较，差异无统计学意义（P＞0．05）。慢性组听皮层c－fos mRNA表达为1．24±0．09，蛋白的表达为0．70±0．12，慢性恢复组听皮层c－fos mRNA的表达为1．23±0．04，蛋白的表达为0．68±0．08，两组均高于正常组（分别为1．12±0．05、0．50±0．04），差异有统计学意义（P＜0．01）。慢性组听皮层TrkB mRNA表达为1．26±0．10，蛋白的表达为1．85±0．17，慢性恢复组听皮层TrkB mRNA表达为1．23±0．07，蛋白的表达为1．80±0．08，均高于正常组（分别为1．11±0．03，1．53±0．16），差异有统计学意义（P＜0．05）。结论长期注射水杨酸钠后大鼠听皮层c－fos基因表达升高，可能与听觉中枢神经活动增强有关；长期注射水杨酸钠可能通过上调大鼠听皮层T rkB的表达，增强听皮层神经营养因子的功能促进听皮层功能重塑。%Objective To study the expression of TrkB and c-fos in rat auditory cortex after long -term ad‐ministration of sodium salicylate and the mechanisms of salicylate ototoxiclty .Methods Normal adult rats were di‐vided into three groups :normal group without any treatment ,long -term treatment group given i .m .injections , 175 mg/kg ,twice daily at 9:00 am and 6 :00 pm for consecutive 14 days and the recovered group using the same method as the chronic group except that they were sacrificed 28 days after salicylate treatment ceased .After the de‐tection of ABR ,rats were sacrificed after deep anesthesia ,and the auditory cortexes were dissected rapidly .Real-time PCR and Western-blot were explored to detect the expression of TrkB and c-fos .Results The average ABR threshold of normal rats was 36 ± 2 .23 dB SPL .The average ABR threshold of long -term group was 41 .3 ± 3 .31 dB SPL ,which was significantly increased than normal group(P<0 .01) .The average ABR threshold of the recoveredgroup was 38 .6 ± 5 .51 dB SPL .There were no differences between the recovered group and normal group(P>0 . 05) .The expression of c-fos mRNA(1 .24 ± 0 .09)and protein(0 .70 ± 0 .12)in the long -term group were signifi‐cantly increased ,when compared with the normal group .The c-fos mRNA(1 .23 ± 0 .04)and protein(0 .68 ± 0 .08) expression in the recovered group were also significantly increased compared with the normal group .The expression of TrkB mRNA(1 .26 ± 0 .10)and protein(1 .85 ± 0 .17)in the long -term group were significantly increased ,when compared with the normal group .The TrkB mRNA(1 .23 ± 0 .07)and protein(1 .80 ± 0 .08)expression in the recov‐ered group were also significantly increased compared with the normal group .Conclusion The inereased expression of c-fos in the long -term group may be related to the enhancement of central auditory function .The inereased ex‐pression of Trk-B in the long -term group might be involved in instability of synaptic plasticity in tinnitus .