Effects of acoustic trauma on the auditory system of the rat: The role of microglia.
Effects of acoustic trauma on the auditory system of the rat: The role of microglia.
复制标题
DOI：
10.1016/j.neuroscience.2015.07.004
复制
发表时间：
2015-09-10
期刊：
影响因子：
3.3
通讯作者：
Salvi RJ
中科院分区：
文献类型：
--
作者：
Baizer JS;Wong KM;Manohar S;Hayes SH;Ding D;Dingman R;Salvi RJ
长时间暴露于大声的声音（声损伤，AT）会导致内毛细胞和外毛细胞（IHC 和 OHC）死亡、螺旋神经节神经元死亡和听神经退化。听神经（8cn）投射到耳蜗核（CN）、耳蜗背核（DC）和腹侧耳蜗核的前（VCA）和后（VCP）三个细分。有解剖学和生理学证据表明 AT 后去神经 CN 发生塑性重组。解剖学发现显示轴突萌芽和突触发生；生理上，自发活动的增加表明电路的重组。这种可塑性背后的机制尚不清楚。最近的数据表明，激活的小胶质细胞除了清除创伤引起的碎片之外，还可能在促进塑料重组方面发挥作用。为了研究声损伤后中枢神经系统中激活的小胶质细胞的作用，我们将动物暴露于足以导致大量毛细胞死亡的双侧噪声中。我们研究了四组不同存活时间的动物：30天、60天、6个月和9个月。我们使用银染色来检查听神经变性的时间过程和模式，并使用免疫组织化学来标记去神经中枢神经中激活的小胶质细胞。我们在 AT 后 30 天、60 天和 6 个月时发现 CN 中存在退化的听觉神经纤维和活化的小胶质细胞。退化纤维和活化小胶质细胞之间存在紧密的地理重叠，这与活化小胶质细胞的清道夫作用一致。在最长的存活时间内，重叠区域仍然存在银染纤维，但激活的小胶质细胞染色很少。然而，周围脑干和小脑白质中存在激活的小胶质细胞。
Exposure to loud, prolonged sounds (acoustic trauma, AT) leads to the death of both inner and outer hair cells (IHCs and OHCs), death of neurons of the spiral ganglion and degeneration of the auditory nerve. The auditory nerve (8cn) projects to the three subdivisions of the cochlear nuclei (CN), the dorsal cochlear nucleus (DC) and the anterior (VCA) and posterior (VCP) subdivisions of the ventral cochlear nucleus. There is both anatomical and physiological evidence for plastic reorganization in the denervated CN after AT. Anatomical findings show axonal sprouting and synaptogenesis; physiologically there is an increase in spontaneous activity suggesting reorganization of circuitry. The mechanisms underlying this plasticity are not understood. Recent data suggest that activated microglia may have a role in facilitating plastic reorganization in addition to removing trauma-induced debris. In order to investigate the roles of activated microglia in the CN subsequent to acoustic trauma we exposed animals to bilateral noise sufficient to cause massive hair cell death. We studied four groups of animals at different survival times: 30 days, 60 days, 6 months and 9 months. We used silver staining to examine the time course and pattern of auditory nerve degeneration, and immunohistochemistry to label activated microglia in the denervated CN. We found both degenerating auditory nerve fibers and activated microglia in the CN at 30 and 60 days and 6 months after AT. There was close geographic overlap between the degenerating fibers and activated microglia, consistent with a scavenger role for activated microglia. At the longest survival time, there were still silver-stained fibers but very little staining of activated microglia in overlapping regions. There were, however, activated microglia in the surrounding brainstem and cerebellar white matter.