Lesions to cochlear inner hair cells induced by noise

Summary A total of 28 un-anesthetized rabbits of the small chinchilla strain were unilaterally exposed to noise (2–7 kHz, 135 dB SPL in the ear canal). After a follow-up time ranging from 15 minutes to 10 months, the ears were perfused with glutaraldehyde and prepared for analysis by secondary emission electron microscopy and or transmission electron microscopy. The typical finding was a fusion and clumping of inner hair cell (IHC) sensory hairs. In two of the animals, no loss of outer hair cells (OHC) was observed; in several of the others, only a small local loss of OHC was observed in the 2 and 4 kHz regions in spite of extensive IHC abnormality. A frequency map of the rabbit cochlea was obtained by pure tone lesions to OHC. The extent of IHC abnormalities corresponds to the 1–16 kHz region. The findings may provide a basis for the study of the functional relationship between the IHC and OHC.Supported by grants from the Swedish Medical Research Council (14X-04958-05B, 12X-03156-09C), Stifteisen Tysta Skolan, K A Wallenberg Foundation, The Swedish Work Environment Fund (79/80) and The Karolinska Institute fundsPresented at the 17th Workshop on Inner Ear Biology in Stockholm, June 23–25, 1980