The effect of chronic application of kanamycin on stereocilia and their tip links in hair cells of the guinea pig cochlea.

Albino guinea pigs were treated with kanamycin (400 mg/kg i.p.) daily for 10 days. After a 2-week recovery period their cochleae were analyzed by scanning electron microscopy. Attention was paid to those outer hair cells which had been less severely damaged. Stereocilia of the outer hair cells were often constricted at the root, and in some cases had become detached at the root. In stereocilia showing any degree of abnormality, the tip links were usually missing. However, in a few exceptional cases, tip links could remain on stereocilia showing other abnormalities, such as constriction at the root. Where hair cells were otherwise apparently unaffected, a much higher proportion of tip links remained, even on cells situated in an area of extensive hair cell loss. The results give further information on the process of kanamycin poisoning. They also suggest that substantial loss of tip links, and therefore perhaps of transduction, is one of the preliminary consequences of kanamycin poisoning.