神经生长因子对大鼠全脑缺血再灌后内耳迟发性毛细胞死亡和听力损伤的影响

目的：研究大鼠全脑缺血再灌注后内耳迟发性毛细胞死亡的变化及神经生长因子(NGF)对其的影响。方法：通过四血管闭塞法建立大鼠全脑缺血-再灌注模型，扫描和透射电镜观察耳蜗毛细胞超微结构改变，40Hz听觉相关电位(AERP)检测听力阈值。结果：缺血再灌组于全脑缺血30min再灌注后1d耳蜗Corti’s器外毛细胞静纤毛倒伏、脱失，再灌注3d出现外毛细胞迟发性死亡，显示细胞凋亡特征。再灌注后1d、3d 40Hz AERP阈值较缺血前显著增高，听力下降，再灌注7d细胞和听力损伤出现修复变化；NGF组再灌注后外毛细胞静纤毛损害明显减轻，未见明显迟发性毛细胞死亡，听力无显著损失。结论：全脑缺血再灌注可引起内耳迟发性毛细胞死亡和听力损失，迟发性毛细胞死亡机制可能是病理性坏死与细胞凋亡共存。NGF能预防和抑制大鼠全脑缺血再灌注所致的内耳迟发性毛细胞死亡和听力损伤。

Inner Ear Delayed Hair Cell Death after Whole Brain Ischemia and Reperfusion and the Effect of NGF in Rats

Objective: To research the changes of inner ear de la yed hair cell death(DHCD) after whole brain ischemia and reperfusion and the eff ect of nerve growth factor(NGF) on hair cell damage. Methods: Whol e brain ischemia and reperfusion rat model was induced by four vessels occlusion . Ultrastructure of cochlear hair cell changes were examined with scanning and t ransmission electron microscopy, and hearing thresholds shifts were tested with 40Hz auditory event related potential (AERP). Results: In the isch emia-reperfusion group, after whole brain ischemia 30 min and reperfusion 1day, cochlear outer hair cells(OHC) stereocilia were lodged or come off, and after r eperfusion for 3days, DHCD were revealed and OHC appeared characteristic alterat ion of apoptosis. The AERP thresholds was significantly higher than before the i schemia(P<0.01) during reperfusion from one day to 3 days with hearing drop ped. The cells and hearing injury were repaired basically after reperfusion for 7 days. In the NGF group, the stereocilia of OHC damage were lightenned markedly , and there was no obvious DHCD.And no obviously threshold shifts was seen in an y of the NGF group rats. Conclusion: Inner ear DHCD and hearing lo ss could be induced by whole brain ischemia and reperfusion, DHCD may be associa ted mechanistically with both pathology necrosis and apoptotic cell death. NGF c an prevent and inhibit inner ear DHCD and auditory injury induced by whole brain ischemia and reperfusion. [