声诱发短潜伏期负电位豚鼠的内耳铺片研究

Inner ear morphological study of guinea pigs with acoustically evoked short latency negative response

目的在耳毒性损伤的豚鼠模型上诱发声诱发短潜伏期负电位（acoustically evoked short latency negativeresponse，ASNR），通过内耳铺片观察ASNR豚鼠的基底膜、球囊、椭圆囊及半规管壶腹的组织形态学特点，验证豚鼠ASNR的责任终器。方法将45只健康豚鼠按随机数字表法分为2组，健康对照组15只（30耳），药物致聋组30只（60耳）。致聋组给药（硫酸卡那霉素＋利尿酸）致聋7～10d后，行听觉脑干反应（ABR）测试，根据ASNR引出情况进一步分为ASNR组和非ASNR组。三组豚鼠断头取颞骨，解剖显微镜下取出基底膜、球囊斑、椭圆囊斑和壶腹嵴，通过显微镜观察毛细胞数目和形态变化。结果致聋组有27只动物（54耳）完成测试，其中45耳达到重度感音神经性聋，19耳引出ASNR（35．2％），阈值为110～125dBSPL，平均阈值（121．7±4．5）dBSPL，潜伏期1．80—2．08ms，平均潜伏期（1．93±0．07）ms。铺片观察显示，基底膜、球囊、随圆囊、壶腹嵴毛细胞密度按正常对照组、ASNR组、非ASNR组依次减低，毛细胞损伤程度依次加重。ASNR组球囊微纹区、周边区毛细胞密度与对照组差异无统计学意义（P值均〉0．05）；其他各组的相应比较，差异均有统计学意义（P值均〈0．05）。结论豚鼠ASNR的责任终器是球囊，而不依赖于耳蜗、椭圆囊及半规管功能。

Objective To establish a model of ototoxicity in guinea pigs with acoustically evoked short latency negative response （ASNR） and verify the responsible organ of ASNR based on microscopic characteristics of basal membranes, saccules, utricles and ampulla canalis semicircularis of the inner ear. Methods Total of 45 guinea pigs were employed in the experiment, which were randomly divided into the control group （15 subjects, 30 ears ） and the deafened group （30 subjects, 60 ears ）. Each animal experienced auditory brainstem response （ABR）. A quick treatment was employed for deafened group consisting of a subcutaneous injection of kanamycin at a dose of 400 mg/kg followed by jugular vein injection of ethacrynic acid at a dose of 40 mg/kg one hour later. The animals were performed ABR test from 7 to 10 days after the drug administration. The deafened group was further divided into ASNR group and non-ASNR group based on the presence of ASNR. All the guinea pigs were sacrificed after ABR tests. The Corti organ, macula sacculi, macula utriculi and crista ampullaris were observed by light microscope. Results In the deafened group （60 ears）, 3 subjects died postoperatively, 27 subjects （54 ears） provided full data; ASNR was elicited in 19 ears （35.2%, 19/54）, the thresholds of ASNR were from 110 to 125 dBSPL with average of （ 121.7± 4. 5）dBSPL. ASNR latency ranges were 1.80-2. 08 ms, the average latency of thresholds were （ 1.93 ± 0. 07） ms. The stretched preparation results ： overall hair-cell density of macula saccule, macula utriculi and crista ampullaris decreased in order of normal control group, ASNR group and non-ASNR group. There was no difference between the normal group and ASNR group for cell density of macula saccule. Apart from this, statistical differences were found among other groups. Conclusions The present study evoked ASNR in an ototoxicity guinea pig model which was profound hearing loss with normal saccular function and normal saccular hair cell density. It suggested that ASNR originates from the saccule and have no relation with cochlear, utricle and semicircular canal according to morphological study.