庆大霉素对豚鼠耳蜗传入神经损伤的电镜观察

Ultrastructural Evaluation of Gentamicin Toxicity on Cochlear Afferent Never Sys tem of Guinea Pig

目的 观察庆大霉素损伤对豚鼠耳蜗传入神经超微结构的影响。方法 听力正常的豚鼠肌注硫酸庆大霉素 (12 0mg/kg) ,连续注射 14天 ,分别于停药后 1天、2周在透射电镜下观察传入神经超微结构改变 ,并进行ABR测听。结果 停药 1天时 ,ABR阈值与正常对照组相比 ,阈值明显升高 (P <0 .0 5) ,停药 2周时 ,ABR阈值进一步升高 ,与 1天时相比 ,亦有显著性差异 (P <0 .0 5)。庆大霉素损伤后 ,随着毛细胞的损伤 ,传入神经末梢肿胀、突触间隙增大 ,传入神经纤维及螺旋神经节损伤程度依次减轻 ;随着损伤时间的延长 ,传入神经末梢的病变加重 ,相应的神经纤维及螺旋神经节的损伤亦加重。结论 在庆大霉素作用下 ,随着毛细胞损伤的加重 ,耳蜗传入神经损伤加重 ,并出现不可逆转性病理改变 。

Objective To study the ultrastructura l changes of gentamicin toxicity on cochlear afferent nerve system in guinea p igs. Methods The guinea pigs were injected with gentamicin (1 20 mg /kg/d im) for 2 weeks, Then the pathologic changes in the afferent nerve ending ,afferent nerve fibers and cell body were evaluated with transmission electron m icroscope at 1 d,2 weeks respectively after gentamicin application, while the a uditory brainstem responses (ABR) threshold was monitored. Results Th e guinea pigs with gentamicin caused significant elevation (P<0.05) of the mean ABR threshold, the threshold of the group of 2 weeks were even higher than t he group of 1 d.The damage of the hair cells, afferent synapses beneath hai r cells were swollen firstly, then the nerve fibers and spiral ganglion cells.The worse the hair cells, the worse the afferent nerve ending ,afferent nerve fiber s and cell bodys. Conclusion Gentamicin could induce irreversible, progress ive afferent neurodegeneration,which is related with the ABR threshold.