The effect of 1 and 6 mM NFA on single Slo2.1 channel activity. (A) Activity of a single Slo2.1 channel in an inside-out patch activated with 1 mM NFA in the pipette solution and recorded during voltage ramps from +80 to −120 mV. For these experiments, the extracellular (pipette) solution contained (in mM): 99 K gluconate, 1 Na gluconate, 2 MgCl₂, 0.1 CaCl₂, 0.1 GdCl₃, 10 HEPES, and either 1 or 6 NFA. The intracellular (cell chamber) solution was the same, except that CaCl₂ was replaced with 2 mM EGTA, and NFA was not present. Three different current traces (i–iii) are shown together with the ensemble average of 15 traces (iv) plotted on a reversed voltage scale. Note outward rectification of currents. (B) A different inside-out patch showing activity of at least two channels that were activated by 6 mM NFA in the pipette solution. Three different current traces (i–iii) are shown together with the ensemble average of 30 traces (iv) plotted on a reversed voltage scale. Note that currents do not exhibit rectification. (C) i-V relationships for single Slo2.1 channels activated by 1 mM (n = 3) or 6 mM (n = 6) NFA. The slope conductance determined from channels activated between −60 and −140 mV was 97 ± 11 pS for 1 mM NFA (n = 3) and 80 ± 2 pS for 6 mM NFA (n = 5).