Tone-induced stereocilia lesions as a function of exposure level and duration in the hamster cochlea.

The present study presents an atlas of the effects of 10 kHz tone exposures of different levels and durations on cochlear hair cells and their stereocilia in the Syrian golden hamster. Animals were sound exposed while under anesthesia. The exposure conditions were varied over an intensity range of 90-129 dB SPL; at the highest levels (126-129 dB SPL) the exposure periods were varied over a range of 30 min to 4 h. In animals with mild damage the lesions were commonly restricted to either the inner hair cells and/or the first row of outer hair cells; the order of damage susceptibility was IHC, OHC1, OHC2, OHC3. Damage to the second and third rows of outer hair cells were found only in animals with the severest lesions. Possible mechanisms underlying the row-specific distributions of these lesions and relative susceptibilities of the 4 rows of hair cells are discussed.