FIGURE 5.

Effects of altering transduction on the flick. (A) Effects of external Ca²⁺ and of gentamicin, a transduction channel blocker. The flick as a function of voltage was not significantly different with 4 mM Ca²⁺ (▪), with 0.1 mM Ca²⁺ (•), or with 0.1 mM Ca²⁺ + 0.2 mM gentamicin (▵) in the external solution. Five other cells showed the same effect. (B) Flick as a function of voltage before (▪) and after (▵) bath application of BAPTA to break tip links (5 mM for 10–20 s, until the receptor current was abolished). Both data sets were recorded with 4 mM Ca²⁺ in the bath solution. The flick was abolished by BAPTA treatment. Four other cells showed the same effect. (Inset) Example of flick movements before and after BAPTA. Scale represents 1 nm and 1 ms. (C) Flick evoked with varying gating spring tension. A cell was depolarized to +40 mV and one of a family of 29 force steps was simultaneously applied to deflect the bundle. Six milliseconds after the start of each force step, the voltage was stepped back to −120 mV, producing a positive-going flick. To measure the size of the flick, bundle positions were averaged 0–0.2 ms before and 0.2–0.4 ms after the voltage step (inset: scale, 1 ms, 1 nm). (D) Flick as a function of force. The flick due to the −160-mV hyperpolarization in C was constant for positive bundle deflections, but rapidly declined to zero below force steps of −16 pN, or −48 nm of bundle deflection. The corresponding receptor current (bottom), measured 1.2 ms after the deflection, declined to near zero at ∼−10 pN.