VARIATION OF COCHLEAR POTENTIALS PRODUCED BY COMPLETE DISPLACEMENT OF ENDOLYMPH IN SCALA MEDIA

The endolymph in the scala media was replaced completely by the isotonic solutions of potassium chloride, sodium chloride, choline chloride and glucose. And also solutions which had variant potassium concentration, or Ringer's solution were used to perfuse the scala media. Then microphonics, summating potentials and action potentials in whole auditory nerve were taken by the vest ib ulo-tympanal recording. Simultaneously endocochlear potentials and negative intracellular potentials in organ of Corti were measured with a micropipette electrode. Variation of those potentials influenced by the displacement of the endolymph, were observed. Consequently both microphonics and action potentials revealed abruptly irreversible decrease in magnitude of the amplitude. Endocochlear potentials were kept relatively high after its gradual decrease. Those facts indicate that high potassium concentration in the endolymph is neccessary to maintain a high sensitibility in the microphonic. Though negative summating potentials and endocochlear potentials increased temporarily during the perfusion, it seemed to originate in dislocation of the basilar membrane to the side of the scala tympani. The post mortal endocochlear potential with negative polarity was present after the perfusion of any kind of solutions. It is comprehended that reverse of the polarity does not relate to the electolyte concentration in the endolymph, but relates to the electric source of potentials at the stria vascularis. When potassium ions disappeared in the endolymph, a very high potential difference between the scala media and the organ of Corti was reduced; however such a reduction was not parallel to the decrease in microphonics.