Stewart Courtney, Yu Yue, Huang Jun, Maklad Adel, Tang Xuehui, Allison Jerome, Mustain William, Zhou Wu, Zhu Hong
PhD Program in Neuroscience, University of Mississippi Medical Center, Jackson, MS, USA; Department of Otolaryngology & Communicative Sciences, University of Mississippi Medical Center, Jackson, MS, USA.
Department of Otolaryngology & Communicative Sciences, University of Mississippi Medical Center, Jackson, MS, USA.
Hear Res. 2016 May;335:118-127. doi: 10.1016/j.heares.2016.03.002. Epub 2016 Mar 10.
Some individuals with noise-induced hearing loss (NIHL) also report balance problems. These accompanying vestibular complaints are not well understood. The present study used a rat model to examine the effects of noise exposure on the vestibular system. Rats were exposed to continuous broadband white noise (0-24 kHz) at an intensity of 116 dB sound pressure level (SPL) via insert ear phones in one ear for three hours under isoflurane anesthesia. Seven days after the exposure, a significant increase in ABR threshold (43.3 ± 1.9 dB) was observed in the noise-exposed ears, indicating hearing loss. Effects of noise exposure on vestibular function were assessed by three approaches. First, fluorescein-conjugated phalloidin staining was used to assess vestibular stereocilia following noise exposure. This analysis revealed substantial sensory stereocilia bundle loss in the saccular and utricular maculae as well as in the anterior and horizontal semicircular canal cristae, but not in the posterior semicircular canal cristae. Second, single unit recording of vestibular afferent activity was performed under pentobarbital anesthesia. A total of 548 afferents were recorded from 10 noise-treated rats and 12 control rats. Noise exposure produced a moderate reduction in baseline firing rates of regular otolith afferents and anterior semicircular canal afferents. Also a moderate change was noted in the gain and phase of the horizontal and anterior semicircular canal afferent's response to sinusoidal head rotation (1 and 2 Hz, 45°/s peak velocity). Third, noise exposure did not result in significant changes in gain or phase of the horizontal rotational and translational vestibulo-ocular reflex (VOR). These results suggest that noise exposure not only causes hearing loss, but also causes substantial damage in the peripheral vestibular system in the absence of immediate clinically measurable vestibular signs. These peripheral deficits, however, may lead to vestibular disorders over time.
一些患有噪声性听力损失（NIHL）的人也报告有平衡问题。这些伴随的前庭症状尚未得到很好的理解。本研究使用大鼠模型来研究噪声暴露对前庭系统的影响。在异氟烷麻醉下，通过插入式耳机让大鼠一只耳朵暴露于强度为116分贝声压级（SPL）的连续宽带白噪声（0 - 24千赫）中3小时。暴露7天后，在噪声暴露的耳朵中观察到听性脑干反应（ABR）阈值显著升高（43.3±1.9分贝），表明出现了听力损失。通过三种方法评估噪声暴露对前庭功能的影响。首先，使用荧光素偶联鬼笔环肽染色来评估噪声暴露后的前庭静纤毛。该分析显示，球囊和椭圆囊斑以及前半规管和水平半规管嵴中的感觉静纤毛束大量丢失，但后半规管嵴中没有。其次，在戊巴比妥麻醉下进行前庭传入活动的单单位记录。从10只经噪声处理的大鼠和12只对照大鼠中总共记录了548条传入神经。噪声暴露使规则耳石传入神经和前半规管传入神经的基线放电率适度降低。水平半规管和前半规管传入神经对正弦头部旋转（1和2赫兹，峰值速度45°/秒）的反应增益和相位也有适度变化。第三，噪声暴露并未导致水平旋转和前庭眼动反射（VOR）平移增益或相位的显著变化。这些结果表明，噪声暴露不仅会导致听力损失，还会在没有即时临床可测量前庭体征的情况下对外周前庭系统造成实质性损害。然而，这些外周缺陷可能随着时间的推移导致前庭障碍。
