Mechanoelectrical transduction by vertebrate hair cells

Abstract

The initial cellular stage in the cat's response to sound is the transduction of mechanical energy into electrical signals of hair cells of the internal ear. This presentation will summarize in vitro experiments on the biophysical basis of transduction and will present a model for the process. Mechanoelectrical transduction rests upon the activity of transduction channels, relatively nonspecific, cation-permeant ion channels. These mechanically sensitive channels, which number about 100 per cell, appear to lie near the distal tip of the hair bundle. Excitatory stimuli cause transduction channels to open with a latency of only a few microseconds; transduction is therefore unlikely to require a second messenger. The dependence of the channels' rate of response upon the stimulus amplitude suggests that stimulation affects the rate constants for channel opening and closing. Mechanical measurements of changes in the bundle's stiffness during channel gating support a model for transduction in which excitatory stimulation acts through an elastic linkage in the hair bundle to open each channel's gate.