In order to clarify the producing mechanism of cochlear microphonics (CM), AC and DC potentials in the organ of Corti were recorded, by introducing a microelectrode through the round, window membrane to the basilar membrane of guinea-pigs. Using the cell-making method, the cell, from which the electric potentials were recorded, was identified by surface preparation technique or cross section. The results are as follows:
1) At the subtectorial space, a positive potential (ca. 60mV) is recorded.
2) By passing through the tectorial membrane, a negative potential is occasionally recorded.
3) In the hair cells, the amplitude of CM increases remarkably.
4) In the supporting cells (especially Claudius's cells and Hensen's cells), the amplitude of CM dosen't increase, but decreases.
5) In the tunnel, the DC potential is zero milli volt, and the amplitude of CM somewhat increases. From these results, it might be suggested that the variable electric potentials at the cuticular lamina, tectorial membrane and subtectorial space influences delicately on the biophysical activity of the sensory hairs, and then have a relation with the production of CM, and the increase and decrease of the amplitude.
