The outer hair cell (OHC) has an important role for the normal function of the cochlea, and the cochlear amplification is believed to be based on OHC electromotility. Although many studies of measuring isolated OHC motility have been done, the whole movement of OHC is still unclear, because most of the measurements have been done by the photodiode technique. In order to understand the shape changes in various points on OHC, the whole movements of OHC were recorded by a high-speed video system when the isolated OHC was whole cell voltage clamped and evoked by low frequency (5Hz) electric stimulus, and displacement of the cell edge and the microbeads attached to the lateral wall of OHC were analyzed by quantifying enhanced grayscale profile shifts in the processed images. The results were as follows: 1. OHC vibrates synchronously in response to the sinusoidal voltage stimuli, and the amplitude of the microbead movements increases with an increase in the distance between the microbead on the cell body and the patch-clamped position. 2. The axial strain in the middle region of OHC is larger than those in the apical and basal regions, and there is no relationship between the patch-clamped position and the strain distribution of OHC. 3. The amplitudes of diameter changes are constant in various points on OHC. 4. There is a possibility that the density of protein motor is largest in the middle region of OHC. However, in order to clarify this possibility, further investigation of measuring the distribution of the OHC axial stiffness from the apical end to the basal end is necessary.
