Figure 9.

btv mutations affect mechanoreceptor potentials but not transepithelial potentials in bristle organs. (A) Recording bristle transepithelial potentials. The decapitated fly is mounted on a chlorided silver pin, which serves as a basal reference electrode. The anterior notopleural (ANP) bristle is cut to half its length, giving access to the lymph in apical extracellular space, and a saline-filled glass microelectrode (outlined by dashed lines), attached to a piezoelectric positioner, is placed over the cut end. The TEP, an apical-positive potential maintained by the ion pumping activity of bristle support cells, is recorded as the voltage difference between the apical and basal electrodes. (B) Representative mechanoreceptor potentials (MRP) recorded from btv⁺ and btv² flies; each trace is an average of 5 trials. The MRP value is the maximal change in TEP immediately following a 10 μm step deflection of the microelectrode and bristle; adaptation is calculated as the % reduction in this change by the end of the 1 s stimulus. C-E: btv mutants show a significant reduction in MRP amplitudes, but no significant change in resting TEP or in adaptation. (C) TEP measured in btv⁺, btv¹, and btv². Each dot represents the TEP of a single bristle. Horizontal bars indicate means, error bars indicate SEM. The point scatter bar on the right includes the data from both btv alleles tested (btv¹ and btv²). TEP is unaffected in btv mutants compared, either separately or together, to btv⁺. (D) MRP is significantly reduced in btv mutants. Symbols as in (C). (E) Adaptation is unaffected in btv mutants. Symbols as in (C).