Some observations on negative endocochlear potential during anoxia.

The effects of anoxia on the endocochlear potential (EP) and +K and +Na concentrations in the endolymph were studied in three groups of guinea pigs: kanamycin-treated guinea pigs, waltzing guinea pigs and normal guinea pigs. The magnitude of the EP in kanamycin-treated guinea pigs and waltzing guinea pigs did not show marked deviation from that observed in normal animals. The +K and +Na concentrations in the endolymph in those animals with severe suppression of sound-evoked cochlear potentials were also within the normal range. The changes in +K and +Na concentrations in the endolymph in anoxic condition were similar in the three groups of animals. However, the rate of decline of the EP was slower in kanamycin-treated guinea pigs and old waltzing guinea pigs. In young waltzing guinea pigs showing moderate suppression on the cochlear microphonics, the decline of the EP during anoxia was comparable to that observed in normal guinea pigs. The results indicate that anoxia decreases +K and increases +Na concentrations in the endolymph in a similar fashion in kanamycin-treated guinea pigs, waltzing guinea pigs and normal guinea pigs. It is suggested that the decline of the EP during anoxia is correlated with the +K conductance of the organ of Corti.