Ashida K
Department of Otolaryngology, Osaka University Medical School.
Nihon Jibiinkoka Gakkai Kaiho. 1992 Dec;95(12):1968-80.
In order to assess the vulnerability of the inner ear, auditory function and morphology of the inner ear were compared between adult budgerigars and adult guinea pigs. Budgerigars have been considered to have an excellent auditory-vocal system. Two experimental conditions were produced in each species; one by acoustic hyperstimulation (1500 Hz, 120 dBSPL) for 96 hours, the other by administration of kanamycin (200 mg/kg) for 7 weeks. Measurement of auditory evoked potentials (AEP) and observation of hair cells by electron microscopy were performed both immediately and 14 days after exposure. In the acoustic hyperstimulation experiment, AEPs of budgerigars showed less damage and better recovery than those of guinea pigs, probably because of morphological differences between the two species in hair and supporting cells. Electron microscopic observation on the budgerigars showed that a small part of the hair cell area was damaged and that regeneration of hair cells had occurred in this area 14 days after exposure. Such observations in guinea pigs revealed that outer hair cells had been damaged and replaced by supporting cells 14 days after exposure. In the kanamycin administration experiment, AEPs showed the same degree of damage and recovery in both species. This suggests that blood supply and drug transport to the inner ear are almost the same although the structure of the inner ear differs markedly between the two species. Electron microscopic observation did not show an apparent regeneration of hair cells 14 days after administration in the budgerigars. Guinea pigs had a tendency to show progressive damage of both auditory function and inner ear morphology even after the cessation of administration. Regeneration of hair cells in the budgerigar differed under both experimental conditions, suggesting that there is a difference in the mode of auditory disturbance between acoustic hyperstimulation and administration of kanamycin. In conclusion, resistance to acoustic hyperstimulation is higher in the avian inner ear than in the mammalian inner ear, while resistance to administration of kanamycin does not differ significantly between the two species.
为了评估内耳的易损性，对成年虎皮鹦鹉和成年豚鼠的听觉功能及内耳形态进行了比较。虎皮鹦鹉被认为具有出色的听觉 - 发声系统。在每个物种中设置了两种实验条件；一种是通过声学超刺激（1500赫兹，120分贝声压级）持续96小时，另一种是给予卡那霉素（200毫克/千克）持续7周。在暴露后即刻及14天后均进行了听觉诱发电位（AEP）测量和通过电子显微镜对毛细胞的观察。在声学超刺激实验中，虎皮鹦鹉的AEP显示出比豚鼠更少的损伤和更好的恢复，这可能是由于两个物种在毛细胞和支持细胞的形态上存在差异。对虎皮鹦鹉的电子显微镜观察表明，毛细胞区域的一小部分受损，并且在暴露14天后该区域出现了毛细胞再生。在豚鼠中的此类观察显示，外毛细胞在暴露14天后已受损并被支持细胞取代。在卡那霉素给药实验中，两个物种的AEP显示出相同程度的损伤和恢复。这表明尽管两个物种的内耳结构明显不同，但内耳的血液供应和药物输送几乎相同。电子显微镜观察在虎皮鹦鹉给药14天后未显示出毛细胞的明显再生。豚鼠即使在停药后仍有听觉功能和内耳形态逐渐受损的趋势。虎皮鹦鹉在两种实验条件下毛细胞的再生情况不同，这表明声学超刺激和卡那霉素给药在听觉干扰模式上存在差异。总之，鸟类内耳对声学超刺激的抵抗力高于哺乳动物内耳，而对卡那霉素给药的抵抗力在两个物种之间没有显著差异。
