Effects of sodium salicylate on evoked-response measures of hearing

The effects of sodium salicylate on auditory sensitivity, frequency selectivity, and temporal resolution were monitored in chinchillas using evoked responses recorded from the inferior colliculus. Administration of sodium salicylate (450 mg/kg/day for 5-15 days) resulted in serum salicylate levels of 25-50 mg/100 ml. The salicylate administration caused elevation of evoked response thresholds (up to 30 dB), mainly at the high frequencies. Frequency selectivity, as estimated by the Q_{10 dB} value of evoked-response tuning curves, was poorer at 4 kHz during drug administration than during the no drug (control) condition. Temporal resolution, as estimated by recovery from forward masking was not significantly poorer during salicylate administration than before administration. However, there was a trend toward longer recovery in animals with large threshold shifts. These results are consistent with models suggesting that salicylate affects the auditory system at the level of the organ of Corti. They also suggest that while the changes in hearing that occur after salicylate administration are consistent with those seen in sensorineural hearing loss, the changes in hearing in the chinchilla are small enough to preclude the use of the drug as a practical model for sensorineural loss.