Microphonic and DC Potentials in the Organ of Corti and the Tectorial Membrane

Microphonic responses and dc potentials recorded within the organ of Corti in guinea pigs were re-examined by means of the marking technique. Marked spots were detected in single cells on surface preparations of the organ of Corti. The result of cell markings substantiates that the negative potential of the organ of Corti is an intracellular potential. The microphonic potential within hair cells was 2 to 4.5 fold larger than that of the extracellular space of the organ of Corti or that of the scala tympani. However, the intracellular microphonics were less than 0.5mV in size of their amplitude.As a microelectrode advanced through hair cells, into the scala media unstable near zero potentials were recorded between the intracellular potential and the endocochlear potential. A phase reversal of microphonics took place in the boundary between the unstable zero potential and the endocochlear potential. All surfaces of the tectorial membrane and a partial surface of the organ of Corti had an affinity for cobalt ions which were injected into the scala media. It is deducible that the unstable zero potential is inside the tectorial membrane. The cover surfaces of the tectorial membrane and the organ of Corti may be related to generation of cochlear microphonics.