Some observations on negative potential in scala media during anoxia Free

It has been widely accepted that the endocochlear potential (EP) is highly dependent on metabolism and changes its polarity almost immediately after onset of anoxia. The origin of the negative potential in the scala media at the early stage of anoxia has not been fully understood. In this study, changes in EP and Na⁺ and K⁺ concentration in the endolymph were measured in anesthetized and immobilized kanamycin‐treated guinea pigs and in waltzing guinea pigs. EP and Na⁺ and K⁺ concentration in the endolymph were in the normal range in those animals, whereas the cochlear microphonic and whole‐nerve action potential were severely suppressed. Under anoxic conditions, rise of Na⁺ and fall of K⁺ concentration in the endolymph did not show significant differences from those found in normal guinea pigs. However, the magnitude of the negative potential in the anoxic cochlea was substantially smaller than that found in normal animals. The mechanism underlying generation of the negative potential in scala media during anoxia is discussed. [Supported by NIH Grant.]