Figure 3.

ACh dose-dependently increases outward current in torus type II hair cells. (A) Outward currents from a torus type II hair cell during a voltage step to −17 mV from a holding potential of −67 mV, during superfusion of external solution (solid line) or the application of 10, 30, 100, and 300 μM ACh (circles). Step protocol in top of first panel applies to all traces. Dotted line represents zero-current level. (B) The amplitude of ACh-sensitive current responses to 3, 10, 30, 100, 300, and 1,000 μM ACh were all normalized to responses to 300 μM ACh. Error bars reflect SEM. Solid line is a Hill Equation fit of the data with EC₅₀ of 76 μM. Number of cells indicated above symbols. (C) Gap-free current clamp recording under zero-current conditions were acquired from a torus type II hair cell during the superfusion of increasing concentrations of ACh (horizontal black bars). Each indicated concentration was applied for 15 s. Hair cells were superfused with external solution in the segments before and after ACh application. Dashed line demarcates the mean baseline zero-current membrane potential.