Permeability of the cochlear partition assessed by electrochemical potential changes during anoxia

We reported that ionic permeability changes in the endolymph‐perilymph barrier contribute a significant factor in the physiological mechanisms underlying the noise‐induced hearing loss (J. Acoust. Soc. Am. 64, S132 (1978)]. An indirect method of estimating permeability changes is to measure alterations of electrochemical potentials during anoxia, from which the contribution of passive ion movement can be calculated. This allows differences of permeability of the endolymph‐perilymph barrier between normal and noise exposed guinea pigs to be indirectly assessed. The endocochlear potential (EP) and $K+$ concentrations of endolymph and perilymph were simultaneously measured in the basal turn of the guinea pig cochlea with a pair of double barreled $K+$ selective electrodes. When anoxia was induced in guinea pigs treated with dihydrostreptomycin, the rate of decline of both EP and chemical potential for $K+$ was reduced compared with normal animals. In guinea pig exposed to broad band noise at 115 dBA for periods ranging from 3 to 17 days, initial results indicate that the decline of the electrochemical potential is reduced but not to the extent found in dihydrostreptomycin treated animals. Results of analysis on electrochemical potential changes in noise exposed guinea pig cochlea during anoxia will be presented.