Figure 6: The activation properties of HCN1 channels are altered by transmembrane voltage changes.
From: Errors in the measurement of voltage-activated ion channels in cell-attached patch-clamp recordings
(a) Voltage-dependent activation of ensemble HCN1 channel activity in cell-attached patches (IC-A) recorded under simultaneous whole-cell (W-C) voltage-clamp from a HEK293T cell. The cell-attached voltage command is shown (Vp). (b) Under whole-cell current-clamp conditions the amplitude of the cell-attached current is decreased (black, top traces). Under these conditions the activation kinetics are accelerated, an effect shown by the overlay of a scaled version of traces recorded under whole-cell voltage-clamp (grey traces). The lower traces show the membrane potential depolarization (Vm) evoked by ensemble channel activity. (c) Intracellular voltage change generated by ensemble HCN1 channel activity. Pooled data (n=9) are presented as mean±s.e.m. and have been fit by linear regression (line). (d) Steady-state voltage–current relationship of ensemble HCN1 channel activity in cell-attached patches under whole-cell voltage- (black symbols) and current-clamp (open symbols) conditions. Grey symbols show the predicted voltage-current relationship when cell-attached currents recorded under whole-cell current-clamp are plotted as a function of the calculated transmembrane potential. Pooled data (n=9) are presented as mean±s.e.m.
