■传导性听力损失(CHL)减弱了将空气传导的声音传递到耳朵的能力。在人类中,严重的听力损失通常伴随着其他神经系统的改变,例如前庭系统;然而,相互关系还没有得到很好的理解。这项研究的总体目标是评估大鼠CHL模型中前庭相关功能的代理。
■雄性Sprague-Dawley大鼠(N=134,250g,2月龄)用于CHL模型中,该模型产生了鼓膜穿刺诱导的>20dB阈值偏移。听觉脑干反应(ABR)记录用于确定CHL前后不同时间的阈值深度。手动和通过自动ABR机器学习算法评估ABR阈值深度。使用旋转杆进行前庭相关功能代理评估,平衡木,电梯垂直运动(EVM)和摩天轮旋转(FWR)测定。
在测试的频率上,与50.69dB±13.98dB(平均值±SD)的后CHL阈值深度相比,前CHL(对照)阈值深度为27.92dB±11.58dB。自动ABR机器学习算法确定了以下阈值深度:Pre-CHL=24.3dB,CHL后同一天=56dB,CHL后7天=41.16dB,在评估的频率(1、2、4、8、16和32kHz)上,CHL后1个月=32.5dB。在持续时间(秒)或速度(RPM)上,CHL前后(〜1周)大鼠的运动功能的旋转评估没有显着差异,尽管前者的影响大小差异很小。CHL后大鼠的平衡梁横向时间明显更长,可能表明运动协调性的变化。Further,仅在CHL大鼠中发现交叉失败。与FWR后的对照大鼠相比,CHL大鼠的缺陷计数显着降低,但不是EVM。对照组和CHL大鼠在EVM后的开放视野检查中行进的总距离显着不同,但不是FWR。EVM与刺激囊的线性加速度(作用在垂直平面上:上下)相关,而FWR与刺激耳石器官和半规管的角加速度(围绕圆形轴的离心旋转)有关;因此,结果的差异可以反映特定的前庭器官功能作用。
■较少的运动(EVM)和增加横向时间(平衡木)可能与焦虑有关,排便模式(FWR)的改变可能是由于听力损失的影响引起的自主神经紊乱。在这方面,导致平衡和运动变化的前庭运动障碍可归因于听觉和前庭功能的调节。未来的研究应该直接操纵CHL大鼠的前庭功能。
UNASSIGNED: Conductive hearing loss (CHL) attenuates the ability to transmit air conducted sounds to the ear. In humans, severe hearing loss is often accompanied by alterations to other neural systems, such as the vestibular system; however, the inter-relations are not well understood. The overall goal of this study was to assess vestibular-related functioning proxies in a rat CHL model.
UNASSIGNED: Male Sprague-Dawley rats (N=134, 250g, 2months old) were used in a CHL model which produced a >20dB threshold shift induced by tympanic membrane puncture. Auditory brainstem response (ABRs) recordings were used to determine threshold depth at different times before and after CHL. ABR threshold depths were assessed both manually and by an automated ABR machine learning algorithm. Vestibular-related functioning proxy assessment was performed using the rotarod, balance beam, elevator vertical motion (EVM) and Ferris-wheel rotation (FWR) assays.
UNASSIGNED: The Pre-CHL (control) threshold depth was 27.92dB±11.58dB compared to the Post-CHL threshold depth of 50.69dB±13.98dB (mean±SD) across the frequencies tested. The automated ABR machine learning algorithm determined the following threshold depths: Pre-CHL=24.3dB, Post-CHL same day=56dB, Post-CHL 7 days=41.16dB, and Post-CHL 1 month=32.5dB across the frequencies assessed (1, 2, 4, 8, 16, and 32kHz). Rotarod assessment of motor function was not significantly different between pre and post-CHL (~1week) rats for time duration (sec) or speed (RPM), albeit the former had a small effect size difference. Balance beam time to transverse was significantly longer for post-CHL rats, likely indicating a change in motor coordination. Further, failure to cross was only noted for CHL rats. The defection count was significantly reduced for CHL rats compared to control rats following FWR, but not EVM. The total distance traveled during open-field examination after EVM was significantly different between control and CHL rats, but not for FWR. The EVM is associated with linear acceleration (acting in the vertical plane: up-down) stimulating the saccule, while the FWR is associated with angular acceleration (centrifugal rotation about a circular axis) stimulating both otolith organs and semicircular canals; therefore, the difference in results could reflect the specific vestibular-organ functional role.
UNASSIGNED: Less movement (EVM) and increase time to transverse (balance beam) may be associated with anxiety and alterations to defecation patterns (FWR) may result from autonomic disturbances due to the impact of hearing loss. In this regard, vestibulomotor deficits resulting in changes in balance and motion could be attributed to comodulation of auditory and vestibular functioning. Future studies should manipulate vestibular functioning directly in rats with CHL.