Electromotile performance of isolated outer hair cells during slow motile shortening

Abstract

ConclusionThe electromotile performance of isolated OHCs does not seem to be dependent on slow motile shortening alone; other mechanisms, such as phosphorylation, are also involved.ObjectiveTo elucidate the relationship between the magnitude of electromotile displacements of outer hair cells (OHCs) induced by mechanical or chemical stimulation over a reversible range, and magnitude of slow motile shortening.Material and methodsIsolated guinea pig OHCs were mechanically (0.6 μl/min perfusion of saline; n=4) or chemically and mechanically (0.6 μl/min perfusion of 12.5 mM KCl; n=4) stimulated in a glass microchamber to evoke slow motile shortening.ResultsCombined mechanical and chemical stimulation evoked greater OHC shortening than mechanical stimulation alone. Both forms of stimulation resulted in reversible shortening. Electromotility was measured using low voltage (±35 mV) and higher voltage (up to ±240 mV) electrical pulses mimicking the receptor potential at different stages of cell shortening. The magnitude of electromotility decreased simultaneously with slow motile shortenings of OHCs. Irrespective of the character of the stimulus (mechanical or mechanical+chemical), the decrease in the magnitude of electromotility was dependent on the degree of cell shortening. Ocadaic acid, a protein phosphatase inhibitor, blocked slow motility and decreased the magnitude of electromotility.