Potentials of outer hair cells and their membrane properties in cationic environments.

The intracellular potentials of outer hair cells were identified by means of Alcian Blue dye marking in the guinea pig cochlea. The d.c. resting potentials were less negative than in the supporting cells. Mean maximal amplitude of the a.c. component in intracellular responses to middle tone stimulation was about 3.8 mV. The phase of the a.c. component was opposite to that of the subtectorial space. The a.c. component decreased as the potential gradient across the sensory hair surface was reduced. Calcium ions and the other divalent cations introduced into the scala media reduced cochlear microphonics roughly in proportion to their concentration. Calcium reduction produced by chelation in the scala media induced the reduction of the microphonics. The intracellular potentials of outer hair cells are unstable and different from those of inner hair cells. Calcium levels may be important in controlling the receptive function of the sensory hair surface, which is exposed to endolymph with a high potassium concentration.