Different effects of noise and salicylate and their interactions on the guinea pig cochlea.

We investigated the effects of noise and salicylate on the guinea pig cochlea by monitoring the acoustic nerve compound action potential (CAP) as well as the 2f1-f2 distortion product in the cochlear microphonics (DP-CM). The alterations of DP-CMs by noise and salicylate revealed an apparent difference, even when the noise-induced and salicylate-induced CAP threshold shifts were equal. This result indicated that noise and salicylate might have an effect on different sites in the cochlea. Combined effects were altered by changing the order in which the two agents were applied. The existing noise-induced damage attenuated the additional ototoxicity of salicylate. In contrast, attenuation did not occur when salicylate administration preceded noise exposure. Considering known effects of noise and/or salicylate altering mechano-electrical transduction (MET) and electro-mechanical transduction of the cochlear outer hair cells, our results seem to suggest that the MET plays a key role in the transduction mechanism in the cochlea.