DC RESTING POTENTIAL IN THE STRIA VASCULARIS OF THE GUINEA PIG COCHLEA

CHANGES OF THE INTRACELLULAR POSITIVE DC POTENTIAL IN THE STRIAL CELLS UNDER VARIOUS CONDITIONS

Abstract

It was clarified that several positive DC steps recorded by inserting a microelectrode through the stria vascularis signify the intracellular potentials of the strial cells in the anxious previous study.
This paper describes an attempt to ascertain the source producing the singular positivity of the intracellular potentials in the strial cells. The intracellular positive DC potentials of the strial cells as well as the EP was depressed markedly by anoxia or the intravenous injection of furosemide. However, it was observed that there was a remarkable difference in the changing pattern between the two potentials. Though the potentials recorded from the strial cells reached low levels, they always remained positive and never changed polarity, while the EP became negative by exhibiting polarity reversal.
Assuming that the positive component of the EP originates from the activity of the electrogenic K-ion pump, this experimental result suggested that the major part of the positivity of the intracellular DC potential is also generated by the action of the K-ion pump which draws K-ion into the strial cells and that the other part of the positivity maintains for a long period of time is probably supported by something else besides the active ion transport. In other words, it seems to be reasonable to consider that the positive DC potential in the strial cells is composed not only of the positive electrogenic potential generated by the active transport of K-ions but also of another potential which causes a positive sign inside the strial cells even when the action of the K-ion pump has completely stopped.
This experiment showed that the electrophoretic microinjection of Na-ions into strial cells, but not the injection of K-ions, decreased the magnitude of the positive intracellular DC potential in these cells. This data indicates that the strial cell membrane is much more permeable to Na-ion than to K-ion, whereas it is common knowledge that the cell membrane generally shows selective permeability to K-ion but not to Na-ion.
Therefore, it can be concluded that the positive Na-ion diffusion potential originating from the Na-ion concentration gradient between the inside and the outside of the strial cell is directly related to the composition of the intracellular positive DC potential of the strial cells in addition to the positive electrogenic potential generated by the active transport of K-ions in the strial cell membrane.