Effects of pure tone on endocochlear potential and potassium ion concentration in the guinea pig cochlea.

Preliminary results presented here indicate a simultaneous decrease in endocochlear potential (EP) and in endolymphatic potassium ion concentration (K+e) under noise exposure. Maximum changes were observed after 20 min and 30 min of sound stimulation, respectively for EP and Ke+. EP recovery was faster than that of K+e. Noise-induced K+e alterations varied with the pure-tone frequency, and the locus along the basilar membrane where the measurements were performed. This supports the hypothesis that the noise has a tonotopic effect correlate with the shape of the travelling wave. Results obtained with ethacrynic acid, administered at the end of the recovery period which followed the noise exposure, indicate that the sound stimulation parameters which were used did not irreversibly alter the ionic transport in the cochlea.