PMC

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.

Phases of the flick, delivered by the fencer on the right (black filled) against the fencer on the left (gray filled), are illustrated by a cartoon. En garde: The initial posture prior to commencing the flick. Backward rotation: The base of the blade is rotated backward, causing the blade to bend forward. Peak backward rotation: The backward rotation of the base of the blade stops causing the blade to bend backwards. Forward rotation: Rapid forward rotation of the base of blade causes the blade to further bend backwards. Deceleration: The forward rotation of the blade is abruptly stopped, causing the blade to markedly bend forward toward the target. If contact is made with adequate force a point, or touch, is scored.

Overview of the FLICK assay
(A) Schematic of steps for data collection using FLICK.
(B) Schematic of steps for analysis of data generated using FLICK.

Flick application