How high endolymphatic DC potentials exist from the basal turn to the apex? This seems to be a clue to clarify the auditory mechanism of, and the impediment to the inner ear.
Method: The recording electrode consisted of a glass micropipette of 5-10 ti diameter, at the tip filled with 3 mol KCI solution in which a silver chloride wire was immersed. This wire was connected with a high input impedance amplifier. The potential difference between the recording micropipette electrode and the indifferent electrode was recorded with a pen writing oscillograph.
The cochlea of anesthetized guinea pigs was exposed through the auditory bulla. A small hole was made in the bony wall of the scala media of each turn except the apex. After compensation of the junction potential the electrode was slowly inserted into the scala media. At the apical turn, however, the hole was made in the scala vestibuli and the electrode was ivserted into the scala media through the Reissner's membrane.
Results: Measurements of the endolymphatic DC potentials were tried in thirty-three cases at the basal turn, in one at the second turn, in two at the third turn and in twelve at the apical turn.
The maxima potentials, we found, were 92 mV at the basal turn, 62 mV at the second turn, 81 mV at the third turn and 83 mV at the apical turn. The modes of the potentials were 70-90 mV at the first turn and 60-70 mV at the apical turn.
Discussion: Misrahy and others found as high as 110-120 mV endolymphatic DC potential in the scala media at the basal turn, but none at the apical turn. On the other hand, Gisselsson reported that the DC potential at the apical turn was as high as at the basal turn.
Our results reveal the existence of nearly the same positive DC potentials inside the scala media of each turn.
