卡那霉素对小鼠耳蜗内毛细胞带状突触数量的影响

目的通过研究卡那霉素对小鼠耳蜗内毛细胞带状突触数量的影响,探讨卡那霉素耳毒性的发病机制。方法实验组昆明小鼠分为6组,每组10只,每日丁胺卡那霉素(400mg/kg)进行肌肉注射,并于第0d、第3d、第7d、第10d、第14d、和第21d取耳蜗基底膜顶回作为标本。对照组(每组10只)采用等体积生理盐水肌肉注射。使用免疫荧光双标法对耳蜗内毛细胞带状突触前膜RIBEYE蛋白和突触后膜GluR2&3蛋白进行标记,激光共聚焦显微镜对耳蜗基底膜顶回进行光学连续切片,运用3dMax8.0软件对带状突触进行三维建模及重构,并观察带状突触形态变化和计算其数量改变。结果所有小鼠耳蜗内毛细胞轮廓完整,但内毛细胞带状突触数量存在差异。与生理盐水对照组相比,在卡那霉素注射初期带状突触数量未见明显变化,给药第7d时内毛细胞带状突触数量显著增加,第21d显著下降。结论卡那霉素连续作用21d,耳蜗内毛细胞带状突触数量呈先增高后降低的趋势。

Effect of kanamycin on the synaptic ribbons of vochlea inner hair cellsin Kunming mice

Objective To explore the mechanism of kanamycin-induced ototoxicity through investigating the change of synaptic ribbons of cochlear inner hair cells in Kunming mice.Methods The mice were intramuscularly injected with kanamycin(400mg/kg) for 21 days and grouped according to administration days.The control group was given the same amount of normal saline at the same time points.Auditory brainstem response(ABR) was performed to assess whether the mice existed hearing loss.The specific presynaptic RIBEYE protein and non-specific postsynaptic GluR2&3 protein in Kunming mouse basilar membrane samples were studied by immunofluorescent labeling.Serial sections were performed on the samples using a laser scanning confocal microscope and used to build three-dimensional models using 3ds Max software to develop the change of synaptic ribbons.Results During the ototoxicitial course induced by kanamycin in mice,the thresholds of ABR in 8kHz stimuli frequency shift upward in a time-dependent manner in drug-administrated mice,but with no significant change in hearing thresholds of ABR in the control group.Membrane profiles of inner hair cells in all mice were intact.The numbers of synaptic ribbons in kanamycin group increased obviously at 7d(<0.01) and but decreased obviously at 21d(<0.01) after administration of kanamycin.Conclusion Ribbon synapses number of inner hair cells increased at 7d,but decreased at 21d after injecting kanamycin.