Density of motility-related charge in the outer hair cell of the guinea pig is inversely related to best frequency

Whole cell voltage clamp and freeze fracture were used to study the electro physiological and ultrastructural correlates of the outer hair cell (OHC) l ateral membrane molecular motors. We find that specific voltage-dependent c apacitance, which derives from motility-related charge movement, increases as cell length decreases. This increasing non-linear charge density predict s a corresponding increase in sensor-motor density. However, while OHC late ral membrane particle density increases, a quantitative correspondence is a bsent. Thus, the presumed equivalence of particle and motor is questionable . The data more importantly indicate that whereas the voltage driving OHC m otility, i.e. the receptor potential, may decrease with frequency due to th e OHC's low-pass membrane filter, the electrical energy (Q x V) supplied to the lateral membrane will tend to remain stable. This conservation of ener gy delivery is likely crucial for the function of the cochlear amplifier at high frequencies. (C) 1998 Elsevier Science Ireland Ltd. All rights reserv ed.