MAPPING THE DISTRIBUTION OF OUTER HAIR CELL VOLTAGE-DEPENDENT CONDUCTANCES BY ELECTRICAL AMPUTATION

The mammalian outer hair cell (OHC) functions not only as sensory rece ptor, but also as mechanical effector; this unique union is believed t o enhance our ability to discriminate among acoustic frequencies, espe cially in the kilohertz range. An electrical technique designed to iso late restricted portions of the plasma membrane was used to map the di stribution of voltage-dependent conductances along the cylindrical ext ent of the cell. We show that three voltage-dependent currents, outwar d K, I-K,I-n, and I-Ca are localized to the basal, synaptic pole of th e OHC. Previously we showed that the lateral membrane of the OHC harbo rs a dense population of voltage sensor-motor elements responsible for OHC motility. This segregation of membrane molecules may have importa nt implications for auditory function. The distribution of OHC conduct ances will influence the cable properties of the cell, thereby potenti ally controlling the voltage magnitudes experienced by the motility vo ltage sensors in the lateral membrane, and thus the output of the ''co chlear amplifier.''