Fig. 4. Time dependence of droperidol block. (  A ) Representative current recordings under control conditions and in the presence of 1 μm droperidol evoked by the “envelope of tails” protocol shown in the inset. (  B ) Average inhibition of the tail current calculated for each depolarization period (Δt) in seven cells. (  C ) The frequency dependence of human  ether-a-go-go -related gene (HERG) inhibition by 1 μm droperidol was investigated after an incubation time of 10 min at −80 mV. Trains of 100 depolarizing pulses, as shown in the  inset , were applied at a basic cycle length of 1 s (Δ; n = 5), 2 s (□; n = 4), 4 s (•; n = 4), or 10 s (○; n = 4). The resulting mean relative tail current amplitudes of the first 60 s are plotted  versus time. The onset of inhibition significantly depended on the basic cycle length (  P < 0.001, analysis of variance), whereas the steady state block was not dependent on the basic cycle length.