Hair cell loss and regeneration in the chick cochlea after treatment with gentamicin.

Hair cells can be damaged by countless agents, among them aminoglycoside antibiotics. In the chick cochlea, the hair cell loss can be recovered by regeneration. The objectives of the present investigation were to study the time progression of injury caused by gentamicin and the regeneration process in chick hair cells. Gentamicin was administered in a single subcutaneous dose of 125 or 250 mg/kg to two groups of 3-day old chicks. The cochleae were processed for analysis by scanning electron microscopy on the 1st, 3rd, 5th and 20th day after injection. The cellular sequence of degeneration and regeneration was studied. On the 20th day, most it he damaged cochlear area showed regenerated hair and support cells. Stereocilia and microvilli were observed on the apical surface of the regenerated hair cells.