Pre-exposure to Lower-Level Noise Mitigates Cochlear Synaptic Loss Induced by High-Level Noise
Pre-exposure to Lower-Level Noise Mitigates Cochlear Synaptic Loss Induced by High-Level Noise
复制标题
预先暴露于较低水平的噪音可减轻高水平噪音引起的耳蜗突触损失
DOI：
10.3389/fnsys.2020.00025
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发表时间：
2020-05-12
影响因子：
3
通讯作者：
Wang, Jian
中科院分区：
文献类型：
--
作者：
Fan, Liqiang;Zhang, Zhen;Wang, Jian
听觉感觉器官似乎较少受到高水平噪声的损害，而高水平噪声是在暴露于非创伤性低水平噪声后出现的。这种现象被称为增韧或调节效应。在功能上，其表现为降低的阈值偏移，并且在形态上表现为减少的毛细胞损失。然而，目前还不清楚是否事先暴露于增韧噪声可以减轻暴露于破坏性噪声引起的突触损失。由于耳蜗内毛细胞和初级听觉神经元之间的传入突触已被确定为一个新的网站参与噪声引起的耳蜗损伤，我们有兴趣在评估是否可以韧化这个突触。在本研究中，突触损失是由破坏性噪声暴露（106 dB SPL）引起的，并在之前暴露于增韧噪声（85 dB SPL）的豚鼠之间进行比较。结果显示，增韧噪声大大减少了暴露于损伤性噪声后1天观察到的突触损失。虽然这是显着的，但增韧噪声对永久性突触丢失的保护作用要小得多。与无噪声暴露的对照组相比，两个增韧组均出现编码缺陷，这反映在复合动作电位（CAP）中的振幅调制信号。一般来说，预暴露于增韧噪声导致高水平噪声引起的突触损失显著减少。然而，这种形态保护并不伴随着强大的功能益处。
The auditory sensory organs appear to be less damaged by exposure to high-level noise that is presented after exposure to non-traumatizing low-level noise. This phenomenon is known as the toughening or conditioning effect. Functionally, it is manifested by a reduced threshold shift, and morphologically by a reduced hair cell loss. However, it remains unclear whether prior exposure to toughening noise can mitigate the synaptic loss induced by exposure to damaging noise. Since the cochlear afferent synapse between the inner hair cells and primary auditory neurons has been identified as a novel site involved in noise-induced cochlear damage, we were interested in assessing whether this synapse can be toughened. In the present study, the synaptic loss was induced by a damaging noise exposure (106 dB SPL) and compared across Guinea pigs who had and had not been previously exposed to a toughening noise (85 dB SPL). Results revealed that the toughening noise heavily reduced the synaptic loss observed 1 day after exposure to the damaging noise. Although it was significant, the protective effect of the toughening noise on permanent synaptic loss was much smaller. Compared with cases in the control group without noise exposure, coding deficits were seen in both toughened groups, as reflected in the compound action potential (CAP) by signals with amplitude modulation. In general, the pre-exposure to the toughening noise resulted in a significantly reduced synaptic loss by the high-level noise. However, this morphological protection was not accompanied by a robust functional benefit.