Figure 2.
Inhibition of single-channel currents by 0.1 µM [spermidine]i. (A) Single-channel recording obtained at +40 mV in the presence of 150 mM of symmetrical [K+]. (B) Single-channel currents recorded with voltage steps from a holding potential of 0 mV in control at the indicated Vm. Segment of 500-ms recordings are shown. (C) Current traces recorded at 0.1 µM [spermidine]i. (D) Amplitude histograms of substates recorded under control conditions and in the presence of 0.1 µM [spermidine]i at +40 mV. (E) i–Vm relationships for the fully open state and the O–S and S–B transitions. (F) The voltage dependence of mean single-channel conductance (open symbols) and chord conductance (closed symbols) in the presence of 0.1 µM [spermidine]i. Black lines show fits to Eq. 1, with A1 = 0.79, A2 = 0.16, Vh1 = +20.8 mV, and Vh2 = +65.0 mV, in terms of the mean γ–Vm relationship, and with A1 = 0.83, A2 = 0.154, Vh1 = +10.6 mV, and Vh2 = +50.4 mV, in terms of averaged G–Vm relationships, in the presence of 0.1 µM [spermidine]i. The z1 and z2 values were set to 5 and 2.8, respectively. n = 2–7. Error bars are not shown when smaller than the symbol.