| Objective: To explore the influence of apoptotic protease, includingcytochrome C （Cyt-C）, cysteine aspartate specific protease （Caspase） andsrc-homology protein tyrosine phosphatase type2（SHP-2） on the plasticity ofcentral auditory system, the expression of Cyt-C, Caspase3and Caspase8onauditory cortical neurons was studied by immunohistochemical method aftercochlear ablation in SD rats, while the expression of SHP-2gene was studiedby real-time quantitative poly chain reaction （RT-PCR） technology.Methods: A total of48two-week-old SD rats （male, level of SPF） wereselected whose auditory brainstem response （ABR） were under15dB soundpressure level （SPL）. They were randomly divided into four traumatizedgroups （2-week,4-week,6-week,8-week） and four control groups （CG）（2w-CG,4w-CG,6w-CG,8w-CG）. The traumatized groups with6rats in eachwere given bilateral cochlear ablation, while the control groups got nodisposal. After operation completed, the ABR threshold of all rats should beabove90dB SPL. Under the same condition, they were allowed to survive fordifferent time according to the need of experiment. Then3rats of each group（bilateral auditory cortex, n=6） were selected for immunohistochemicaldetection, while the other3（n=6） for RT-PCR detection of SHP-2gene, untilthe histological sections of the auditory cortex were evaluated with both H&Eand Nissl staining. At last, immunohistochemical detection was adopted forCyt-C, Caspase3, Caspase8, and the brown positive cells were counted by the40×10times optical microscope with color image processing software, aswell as RT-PCR detection was adopted for SHP-2gene, whose relativequantity in each group was calculated by means of2-△△Ct.Results: The stable and reliable model of auditory deprivation in rat wasso successfully established that the threshold of ABR at95dB SPL could not arouse repetitive waveforms, with significant difference （P <0.01） betweenpre-operation and post-operation. In tissue section stained for H&E, comparedto the control group, volume was more shrinking and color was morehyperchromatic in neurons of each traumatized group （cytoplasm and karyonwere both as unclear as karyotheca and nucleolus）. In addition, The number ofpositive Cyt-C was30.9±1.65at2-week,1.7±0.14at2w-CG,33.0±2.15at4-week,2.3±0.16at4w-CG,37.0±3.27at6-week,1.8±0.14at6w-CG,42.2±2.36at8-week,2.0±0.16at8w-CG, with statistical differences （P <0.05） both between each traumatized group and its control group and betweenany two traumatized groups. The number of positive Caspase3was27.4±2.88at2-week,2.1±0.14at2w-CG,28.7±2.89at4-week,1.8±0.15at4w-CG,35.2±3.17at6-week,2.1±0.13at6w-CG,44.0±2.56at8-week,2.4±0.13at8w-CG; the significant differences （P <0.05） were not onlybetween each traumatized group and its control group, but also between4-week and6-week,4-week and8-week,6-week and8-week, except2-weekand4-week. The number of positive Caspase8was28.4±2.08at2-week,1.9±0.16at2w-CG,29.3±2.08at4-week,2.0±0.15at4w-CG,37.4±1.73at6-week,2.3±0.18at6w-CG,40.2±2.22at8-week,2.1±0.17at8w-CG; thesignificant differences （P <0.05） were not only between each traumatizedgroup and its control group too, but also between4-week and6-week,4-weekand8-week,6-week and8-week, except2-week and4-week too. Ultimately,the relative expression （compared to the control group） of SHP-2gene was1.1±0.28at2-week,1.5±0.04at4-week,2.5±0.08at6-week,11.0±0.06at8week, with statistical differences between any two （P <0.05）.Conclusion: Firstly bilateral cochlear ablation was a reliable way toestablish the model of auditory deprivation in rat. Secondly the speed ofneuronal apoptosis in auditory cortex caused by bilateral cochlear ablation waslower before4weeks and quicker after6weeks. Thirdly the positive adjustment by SHP-2gene existed in the apoptosis, with positive correlationto the time. |
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