The Effect of Sodium Deficiency on Cochlear Potentials

Abstract

The scala vestibuli and/or scala tympani in guinea pigs were perfused with Na+ free Locke's solution, in which NaCl was replaced with either choline chloride or sucrose. Cochlear microphonics (CM), summating potential (SP), action potential (AP), and endocochlear potential (EP) were recorded from the basal turn before, during, and subsequent to, the perfusion. Complete replacement of the perilymph with Na+-free solution did not alter EP and CM immediately, although AP was abolished rapidly. Lack of Na in the perilymph of scala tympani depressed AP more markedly than did a comparable deficiency in scala vestibuli. In most cases, the depression of AP was reversible and EP and CM showed a gradual decline after the perfusion. These data were further confirmed by the fact that tetrodotoxin at a concentration of 50λ/l did not modify EP and CM, although AP was abolished promptly. The mechanism underlying the generation of the receptor potential is discussed. [Work supported by National Institutes of Health, Public Health Service, U. S. Department of Health, Education and Welfare.]