Damage and regeneration of hair cell ciliary bundles in a fish ear following treatment with gentamicin.

Sensory hair cells in the striolar regions of the utricle and lagena of a teleost fish, the oscar (Astronotus ocellatus), were damaged following intramuscular injections of gentamicin sulfate. In order to determine whether fish can regenerate hair cells, the time course of damage and recovery was followed over a period of four weeks by scanning electron microscopy. Maximum loss of ciliary bundles occurred at about day 10 after the first of four daily injections of gentamicin (20 mg/kg) in 4-6 cm long fish. The striolar regions were almost totally denuded of ciliary bundles, and there was evidence of considerable hair cell loss. The time course for damage was longer in larger fish, but the recovery of the ciliary bundles appeared to be complete about 10 days after maximal damage was seen in both the smaller and larger fish. These data indicate that Astronotus is able to repair damage to hair cells for an extended period of time post-embryonically.