Audiometric and histologic comparison of noise‐ and drug‐induced cochlear pathology in the chinchilla

The purpose of this investigation was to compare audiometric and histologic evidence of drug‐ and noise‐induced hair cell pathology present in the chinchilla two and six weeks after the end of treatment. Behavioral audiometry was accomplished using a shock‐avoidance conditioning paradigm, cochlear tissues were prepared using a surface preparation technique and cellular damage was estimated by means of interference‐contrast microscopy. Results of the study indicate that after drug treatment the location of hair cell damage and the frequencies where hearing loss occurred agreed fairly well but the number of damaged hair cells and the amount of threshold shift did not. Less cellular damage was present six weeks than two weeks after the end of drug or noise treatment. The implications of large individual variations between animals is discussed.