ENT Institute, Eye & ENT Hospital of Fudan University, Fenyang Road 83, Shanghai 200031, PR China; NHC Hearing Medicine Key Laboratory (Fudan University), Shanghai, PR China.
ENT Institute, Eye & ENT Hospital of Fudan University, Fenyang Road 83, Shanghai 200031, PR China; NHC Hearing Medicine Key Laboratory (Fudan University), Shanghai, PR China; Department of Facial Plastic and Reconstructive Surgery, Eye & ENT Hospital of Fudan University, Fenyang Road 83, Shanghai 200031, PR China.
Auris Nasus Larynx. 2020 Oct;47(5):769-777. doi: 10.1016/j.anl.2020.03.008. Epub 2020 May 11.
To investigate the effects of long-term moderate noise on hearing functions, MOCR, and MEMR.
Mice were exposed to the moderate noise (11.2 - 22.4 kHz, 80 dB SPL, 6 h/day, 4 weeks). Subsequently, the hearing functions, including threshold and input-output roles of ABR (auditory brainstem response) and cubic (2f-f) DPOAEs (distortion product otoacoustic emissions) were evaluated. Also, MEMR and MOCR were assessed shortly after or at four weeks following the termination of exposure to the noise.
The mice's acoustic suppression reflex was strengthened, hearing functions and MEMR were unaffected four weeks after the moderate noise. For primary tones of 16, 20 and 24 kHz, the strengths of contralateral and ipsilateral suppression in the noise group were about double those recorded in the control group. In order to further determine whether the functional changes of the afferent or efferent nerves increased the strengths of acoustic suppression, the mouse's left ear was inserted the earplug, and then exposed the moderate noise for four weeks. The strengths of contralateral suppression at 16, 20 and 24 kHz were increased for the noise + earplug than for the control group and were indistinguishable between the noise + earplug and the noise group. While no significant changes were found in the strengths of ipsilateral suppression at all frequencies for the noise + earplug group compared with the control group. Under ketamine/xylazine anesthesia, the broadband suppressor noise did not stimulate the MEMR by 20 min post-induction at all frequencies in three groups.
Our data demonstrated that the long-term moderate noise-exposure strengthened mice's MOCR by changing its afferent nerves, and unaffected cochlear hair cells and type I spiral ganglion neurons.
研究长期中度噪声对听力功能、MOCR 和 MEMR 的影响。
小鼠暴露于中度噪声（11.2-22.4 kHz，80 dB SPL，6 h/d，4 周）。随后，评估听觉脑干反应（ABR）和立方（2f-f）畸变产物耳声发射（DPOAEs）的阈值和输入-输出功能。此外，在暴露于噪声后不久或终止后 4 周评估 MEMR 和 MOCR。
小鼠的声抑制反射增强，中度噪声暴露 4 周后听力功能和 MEMR 不受影响。对于 16、20 和 24 kHz 的基频，噪声组的对侧和同侧抑制强度约为对照组的两倍。为了进一步确定传入或传出神经的功能变化是否增加声抑制的强度，将小鼠左耳插入耳塞，然后暴露于中度噪声 4 周。与对照组相比，噪声+耳塞组在 16、20 和 24 kHz 时的对侧抑制强度增加，与噪声组无明显差异。而噪声+耳塞组在所有频率时同侧抑制强度与对照组相比均无明显变化。在氯胺酮/甲苯噻嗪麻醉下，三组在诱导后 20 分钟内，宽带抑制噪声在所有频率均不能刺激 MEMR。
我们的数据表明，长期中度噪声暴露通过改变传入神经增强了小鼠的 MOCR，而对耳蜗毛细胞和 I 型螺旋神经节神经元没有影响。
