红外线激光刺激豚鼠耳蜗诱发听性脑干反应作用靶点的实验研究

The study on the targets of the optical evoked auditory brainstem response on the cochlea of guinea pig stimulating by infrared laser

目的研究红外线激光刺激豚鼠耳蜗诱发听性脑干反应（optical evoled auditory brainstem response，oABR）的作用靶点，探讨激光刺激的作用机制。方法对正常听力豚鼠及急性耳蜗损伤豚鼠耳蜗植入直径200 μm的光纤（NA＝0.22），光纤末端对准鼓阶不同部位进行激光刺激，记录并比较不同刺激角度下oABR的反应情况及正常听力与急性耳蜗损伤豚鼠oABR阈值和波幅之间的差异。刺激结束后，取耳蜗分别进行免疫荧光染色，观察给药后7 d内、外毛细胞的改变及螺旋神经节细胞的改变，并比较与oABR改变之间的相关关系。以SPSS 18.0软件对数据进行统计学分析。结果急性耳蜗损伤豚鼠在给药后7 d，耳蜗底圈、中圈内、外毛细胞损伤，顶圈内、外毛细胞仍残留。当光纤对准Rosenthal′s管方向刺激时，无论正常听力豚鼠或是毛细胞损伤豚鼠，均可得到稳定的oABR，当光纤偏离Rosenthal′s管方向刺激时，如指向基底膜方向或指向鼓阶纵深时，均无法引出oABR。结论红外线激光刺激耳蜗诱发oABR是通过直接作用于螺旋神经节细胞产生的。

ObjectiveTo identify the targets of the infrared laser stimulating on the cochlea of guinea pig which evoked auditory brainstem response （oABR）, and explore the mechanisms of the infrared neurostimulation. MethodsA polished optical fiber with 200 μm diameter （NA=0.22） was planted into the scala tympani of guinea pigs to stimulate the cochlea of both the normal hearing and acute deafened guinea pigs. The direction of the fiber distal was changed to radiate different regions of the scala tympani, recording the oABR respectively. Differences of energy thresholds and amplitudes of oABR between normal hearing and acute deafened animals was concerned, and different responses were recorded as the optical path of laser fiber being changed to investigate the targets of the infrared laser stimulation. Immunofluorescence was used to detect the changes of inner and outer hair cells, and spiral ganglion neurons 7 days post-deafening, to looking for the probable association with the oABR changes at the same stimulus. SPSS 18.0 software was used to analyze the data.ResultsInner and outer hair cells were damaged in basal and middle turn, butresidual hair cells were observed in apical turn.Only when the optical fiber pointed to Rosenthal＇s canal stimulated the spiral ganglion region directly could the oABR be evoked. No response was recorded while the fiber pointed to other directions. ConclusionInfrared laser stimulates cochlea evoked oABR generats from the response of spiral ganglion directly, the spiral ganglion neurons are the target of infrared stimulation.