Effect of Salicylate and Short-term Sound Exposure on Extracochlear Electrically-evoked Otoacoustic Emissions

Abstract

The effects of salicylate and acoustic overstimulation on the electromotility of the cochlear outer hair cells (OHCs) were assessed in vivo using electrically-evoked otoacoustic emissions (EEOAEs). Alternating currents to evoke the EEOAE were delivered by means of an extracochlear electrode on the round window, with which the compound action potentials (CAPs) were also monitored before and after the manipulations. The EEOAE outputs were a linear function of the injected currents between 52 and 267 w A rms. Administration of salicylate (500 mg kg) reduced the EEOAE outputs significantly at 5 and 8 kHz ( p <0.005), while no change in EEOAEs was observed at any frequency after exposure to a 4 kHz pure tone at 100 dB SPL for 10 min or at 120 dB SPL for 30 min. These results indicate that administration of salicylate reduces the electromotility of the OHCs, and thus produces losses in neural sensitivity of the cochlea. In contrast, the electromotility of OHCs appears to be protected against short-term intense sound exposure.