Durham D, Park D L, Girod D A
Department of Otolaryngology and the Smith Mental Retardation and Human Development Research Center, University of Kansas Medical Center, Kansas City 66160-7380, USA.
Hear Res. 2000 Sep;147(1-2):145-59. doi: 10.1016/s0378-5955(00)00128-3.
Following cochlear ablation, auditory neurons in the central nervous system (CNS) undergo alterations in morphology and function, including neuronal cell death. The trigger for these CNS changes is the abrupt cessation of afferent input via eighth nerve fiber activity. Gentamicin can cause ototoxic damage to cochlear hair cells responsible for high frequency hearing, which seems likely to cause a frequency-specific loss of input into the CNS. In birds, these hair cells can regenerate, presumably restoring input into the CNS. This review summarizes current knowledge of how CNS auditory neurons respond to this transient, frequency-specific loss of cochlear function. A single systemic injection of a high dose of gentamicin results in the complete loss of high frequency hair cells by 5 days, followed by the regeneration of new hair cells. Both hair cell-specific functional measures and estimates of CNS afferent activity suggest that newly regenerated hair cells restore afferent input to brainstem auditory neurons. Frequency-specific neuronal cell death and shrinkage occur following gentamicin damage to hair cells, with an unexpected recovery of neuronal cell number at longer survival times. A newly-developed method for topical, unilateral gentamicin application will allow future studies to compare neuronal changes within a given animal.
在耳蜗切除后，中枢神经系统（CNS）中的听觉神经元会在形态和功能上发生改变，包括神经元细胞死亡。这些中枢神经系统变化的触发因素是通过第八神经纤维活动传入输入的突然停止。庆大霉素可对负责高频听力的耳蜗毛细胞造成耳毒性损伤，这似乎可能导致传入中枢神经系统的输入出现频率特异性丧失。在鸟类中，这些毛细胞可以再生，大概能恢复对中枢神经系统的输入。这篇综述总结了目前关于中枢神经系统听觉神经元如何应对这种耳蜗功能的短暂、频率特异性丧失的知识。单次全身注射高剂量庆大霉素会导致高频毛细胞在5天内完全丧失，随后新的毛细胞再生。毛细胞特异性功能测量和中枢神经系统传入活动估计均表明，新再生的毛细胞可恢复对脑干听觉神经元的传入输入。庆大霉素损伤毛细胞后会发生频率特异性神经元细胞死亡和萎缩，在较长存活时间时神经元细胞数量会意外恢复。一种新开发的局部单侧应用庆大霉素的方法将使未来的研究能够比较给定动物体内的神经元变化。
