高血圧自然発症ラット(SHR)の内耳病態
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概要
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Although it is a common impression of otolaryngologists that hypertension or arteriolosclerosis may cause hearing impairment, there has been no conclusive study done in this area. The purpose of this study is to examine and clarify the effect of long-term hypertension on the cochlea of an animal model.Spontaneously hypertensive rats (SHR) and Wistar rats Kyoto (WR), ranging in age from 1-24 months, were used as experimental and control animals, respectively.The cochleas fo rats of both strains were examined electrophysiologically and electromicroscopically. The Cochlea was exposed under methoxyflurane anesthesia and a needle electrode was placed on the bony cochlea. Cochlear microphonics (CM) and action potential (AP) were obtained by the electrocochleographic method in response to tone burst and click. The visual detectable threshold and the maximal out-put were used as indicators of hearing activity and were plotted in terms of age.The cochlea was embedded in Epon, and ultra-thin sections were obtained and examined by electronmicroscopy. In some cochleas, the organ of Corti was examined in the form of surface preparations stained with succinic dehydrogenase.The threshold of the cochlear potentials of SHR increased progressively with age. Conversely the maximal out-put decreased progressively. The degree of progression was larger in SHR than in WR. With increasing age pathological changes were observed diffusely in both the vascular stria and the organ of Corti. The degree of change was again larger in SHR than in WR. However, there was no apparent difference in the nature of the changes in the two strains.It is most likely that hypertension is a factor in the aging of the cochlea and presbycusis. The mechanism for this is discussed briefly.
- 耳鼻咽喉科臨床学会の論文