Mechanisms of hair cell tuning

Mechanosensory hair cells of the vertebrate inner ear contribute to acousti c tuning through feedback processes involving voltage-gated channels in the basolateral membrane and mechanotransduction channels in the apical hair b undle. The specific number and kinetics of calcium-activated (BK) potassium channels determine the resonant frequency of electrically tuned hair cells . Kinetic variation among BK channels may arise through alternative splicin g of slo gene mRNA and combination with modulatory beta subunits. The numbe r of transduction channels and their rate of adaptation rise with hair cell response frequency along the cochlea's tonotopic axis. Calcium-dependent f eedback onto transduction channels may underlie active hair bundle mechanic s. The relative contributions of electrical and mechanical feedback to acti ve tuning of hair cells may vary as a function of sound frequency.