Slo2.1 channel rectification is greater than that predicted by GHK current equation. (A) Single Slo2.1 channel activity measured in an excised inside-out patch during a voltage ramp as indicated. Extracellular (pipette) solution contained (in mM): 90 NaCl, 10 KCl, 0.1 CaCl2, 2 MgCl2, 10 HEPES, and 1 NFA, pH 7.2; intracellular (bath) solution contained (in mM): 90 KCl, 10 NaCl, 2 EGTA, 10 HEPES, and 2 MgCl2, pH 7.2. The holding potential was −80 mV, and the voltage was stepped to +80 mV, and then ramped down to −120 mV over 775 ms. The slope conductance for this single channel at positive potentials was 55 pS. (B) Ensemble average currents recorded during 37 voltage ramps. The red curve represents the i-V relationship predicted by the GHK current equation for a voltage-independent conductance.
