ASYMMETRIES IN MOTILE RESPONSES OF OUTER HAIR CELLS IN SIMULATED IN VIVO CONDITIONS

It is now well known that electrical stimulation of isolated mammalian outer hair cells results in a motile response (Brownell, 1983;Ashmore,1987;Zenneret al.,1987). The fast response component is apparently capable of following a sinusoidal current stimulus in the audio frequency range (Ashmore, 1987; Zenner et al., 1987). Fast motility is a robust response that has been shown under conditions that are distinctly non-physiological. In all experiments reported thus far, all cell surfaces were bathed in a high-sodium medium. Of course, under in vivo conditions only the basolateral cell membrane is exposed to perilymph (high Na+) while the hair-bearing apical end is bathed in endolymph (high K+). We demonstrate here that isolated cells show two kinds of rectification in their motility with sinusoidal current stimuli, that there are quantitative differences in the responses as a function of cell length, and that these phenomena persist when the apical and basolateral cell surfaces are exposed to their proper biochemical environment.