噪声暴露致听神经到耳蜗核神经通路电生理特性的改变

The Changes of the Electrophysiological Characteristics in the Pathway from Auditory Nerve to Cochlear Nucleus after Noise-exposure in Mouse

目的通过研究噪声暴露致小鼠听力损伤后,耳蜗背侧核的兴奋性梭形神经元和耳蜗腹侧核的抑制性D型星形神经元接受听觉神经输入的电生理特性改变,探索噪声致听觉系统外周损伤后引起的中枢神经通路的变化。方法30只健康成年的转基因小鼠SOM-tdTomato采用随机数字表法随机分为对照组(15只,不给予任何噪声暴露)、噪声暴露组(15只,120 dB SPL白噪声每天暴露4 h,连续暴露7 d)。应用听性脑干反应(ABR)测试两组小鼠的听功能,应用膜片钳离体脑片技术分析比较两组小鼠听觉神经到耳蜗核的梭形神经元和D型星形神经元投射通路电生理特性的改变;应用免疫荧光染色法确定记录神经元的类型。结果与对照组比较,噪声暴露组小鼠短声和短纯音ABR反应阈值升高,波Ⅲ潜伏期延长(P<0.05)。膜片钳离体脑片记录结果表明:两类神经元都表现有来自听神经的兴奋性突触后反应,与对照组比较,噪声暴露组反应幅度降低、概率下降、延时延长,其中对D型星形神经元的支配效率降低更多。结论听觉神经可以直接支配耳蜗核的梭形神经元和D型星形神经元;噪声损伤听力后,这种支配效率和强度均明显降低。

Objective To study the changes in central nervous pathways caused by noise-induced peripheral damage,by comparing the change of electrophysiological characteristics from auditory nerve to cochlear nucleus after noise exposure and studing the properties of the excitatory fusciform neurons in the dorsal cochlear nucleus,and inhibitory D-stellate neurons in the ventral cochlear nucleus.Methods A total of 30 healthy transgenetic mice of SOM-tdTomato were randomly divided into the control group(15 mice,no noise exposure),and the noise exposure group(15 mice exposed with 120 dB SPL white noise for 4 hours per day for continuous 7 days),respectively.ABR was applied to test the hearing function of SOM-tdTomato mice in the control and noise exposure group.Brain slice patch clamp recording was performed to compare the microcircuit change from auditory nerve to the fusciform and D-stellate neurons.Immunoflurescence staining was used to determine the type of recorded neuron.Results There was significant difference in hearing function between the control and noise exposure group.Click and tone burst ABR test showed increased ABR threshold and longer duration of waveⅢafter noise exposure(P<0.05).The excitatory postsynaptic responses were recorded in both fusciform and D-stellate neurons by brain slice patch clamp recording.There was decreased in response amplitude,longer response duration and decreased in response probability after noise exposure.The auditory nerve showed lower innervation efficiency to D-stellate neuron.Conclusion Auditory nerve can directly innervate both the fusciform and D-stellate neurons.After noise exposure,both the efficiency and intensity of this innervation were significantly reduced.