Study Of The Mechanism Of Age-related Hearing Loss And Noise Induced Hearing Loss

Objective: 1.To study the expression of prestin protein in hair cells of different age groups in 129 SV mice,to explore the functional changes of outer hair cells in different age groups,and to reveal the role of outer hair cell function changes in age-related deafness.2.To study the effects of moderate-intensity band-pass noise exposure on hearing and internal and external hair cells of C57 mice.Methods: 1.1 The 5C,26 W,52W mice were subjected to nonlinear membrane capacitance recording of outer hair cells.The differences of I-V curve,Qmax,Clin,Vh and Qsp in different age groups were analyzed.1.2 The auditory brainstem response test was performed on 5W,26 W,52W mice,and the hearing thresholds of 4 k Hz,5 k Hz,8 k Hz,11 k Hz,16 k Hz,22 k Hz,and 32 k Hz were obtained for each group of mice.The threshold values of mice of different ages were compared.1.3 According to the measured ABR data,the ABR amplitude analysis was performed on the 8 k Hz frequency of 5W,26 W,52W mice,and the amplitude and latency of their ABR I waves were obtained and compared.1.4 The endolymphatic potential test was performed on 5W,26 W,52W mice to analyze the difference of lymphatic potential in mice of different ages.2.1.Noise exposure to C57 BL/6 male mice for 2 hours with 98 d B SPL,8-16 k Hz bandpass noise.2.2.Auditory brainstem response tests were performed before noise exposure,on the first day and fifteenth day after noise exposure to observe the damage and recovery of noise caused by noise.2.3.Non-noise mice were used as the control group,and the mice on the 15 th day after noise exposure were set as the experimental group.Immunofluorescence staining was performed on the basement membrane of the control group and the experimental group,and the inner and outer hair cells and inner hair cells were used.The banded synapses are counted.Results: 1.The results of ABR test showed that there was no significant threshold increase in 26 W mice compared with 5W mice,and there was no significant change in ABR I wave amplitude latency,but the threshold of 52 W mice increased at full frequency,accompanied by ABR I wave amplitude drop and latency delay.2.The results of non-linear membrane capacitance recording of outer hair cells showed that the nonlinear membrane capacitance(Qmax)and current maximum(Imax)of 26-week-old mice decreased significantly compared with 5 weeks of mice when given Ramp voltage stimulation.At the same time,the linear film capacitance(Clin),charge density(Qsp),and the semi-activated voltage(Vh)of the nonlinear film capacitance did not change significantly.Compared with the 5th week old mice,the Qmax,Clin,QSP,and Imax of the outer hair cells of the 52-week-old mice decreased significantly,and Vh shifted to the depolarization direction.3.The high-frequency threshold of C57 mice did not fully recover on the fifteenth day after noise exposure.At 22 k Hz,the ABR I wave amplitude of the experimental group was significantly decreased,and the latency was significantly prolonged.Immunofluorescence staining showed that the outer hair cells were significantly lost in the high frequency region after noise,and the inner hair cell ribbon synapses were significantly lost in the high frequency region.Conclusion: 1.Loss of Prestin protein in outer hair cells plays an important role in the development of senile sputum.2.98 d B bandpass noise exposure will produce a mild permanent threshold shift in C57 BL/6 male mice,and the damaged basement membrane area will be concentrated in the mid-high frequency region.Compared with outer hair cells,the frequency range of synaptic structure and functional damage of inner hair cells after noise is more extensive.