Hyposmotic swelling induces magnitude and gain change in the electromotile performance of isolated outer hair cells.

OHCs were inserted into a partitioning microchamber. Reversible swelling was induced by hyposmotic incubation medium (270 mos.kg H2O-1). The transfer curve of electromotility was measured by stimulating the OHCs with a series of brief (2.5 ms) square-pulses with both polarities and graded magnitudes. Response magnitude and gain of electromotility were increased in swollen OHCs. On the basis of their electromotile performance-characteristics, swelling appeared to depolarize the OHCs. Transition from contraction dominated asymmetry of motility was observed towards a symmetric response. Depolarization, by itself, cannot explain the gain and magnitude increase. Acetylcholine (ACh) responsiveness of swollen OHCs preserves the pre-challenged pattern: ACh further increases gain and magnitude.