Figure 1.

Mechanotransduction and hair bundle movements in chicken SHCs. (A) Surface view of chicken basilar papilla showing the hair bundles of SHCs, orientation indicated by Ab (abneural) and N (neural) sides. Note the bundles are eccentrically located towards the abneural edge of papilla. (B) MT currents in response to saturating bundle motion elicited by sinusoidal fluid jet stimuli. In the stimulus monitor (top) the thin line is the calibrated photodiode current superimposed on the driving voltage to the fluid jet piezoelectric disk. The MT current throughout the first cycle is plotted against bundle displacement, ΔX (bottom) and is fitted with a Boltzmann equation (dashed line) with I_MAX of −0.64 nA and 10-90 per cent working range (see Methods) of 37 nm. In this and subsequent current-displacement relations, the absolute amplitude of the current is plotted. (C) Depolarizing voltage step (top) from −84 to +56 mV generates a partially inactivating membrane current (middle) and a deflection of a free-standing bundle (bottom) which is predominantly negative (away from the tallest edge of the bundle). (D) Set of depolarizing voltage steps in another SHC generates negative bundle movements graded with the depolarization. In this case, a flexible glass fiber, stiffness 1.2 mN/m, was attached to the hair bundle allowing calculation of forces produced (bottom, right hand axis).