Capacitive binding signals for the hydrophobic Cl⁻ channel blocker, NFA (0.2 mM), are nearly unchanged by MEND. BHK cells with standard solutions. (A) The application and removal of NFA causes a robust increase of C_m. Decay of the C_m signal occurs in two distinct phases. Currents associated with NFA application are very small, or absent, and show a delay from the onset of the rise of C_m. (B) The capacitance–voltage relation of the NFA signal is nearly flat, indicating that capacitive signals do not arise from translocation of the probe across the membrane. (C) The capacitive signal induced by NFA is unaffected by TX100-induced MEND. (D) MEND induced by Ca influx in the presence of 2 mM EDA in both cytoplasmic and extracellular solutions. The capacitive signal induced by NFA rises and falls faster after Ca-induced MEND, but its magnitude is not affected. (E) Effect of Ca influx associated with exocytosis without MEND on NFA-capacitive signals. Cytoplasmic solutions contain no ATP and no polyamine. The Ca transient results in a 60% increase of C_m and a smaller increase of the NFA signal. After a second Ca transient, the NFA signal is nearly doubled and becomes faster.