Figure 4. Voltage-current analysis of I_H blockade.

A, voltage responses (lower) to 2.5 s current pulses (upper) were recorded from a MNC in the absence (control) and presence of 66 μm ZD 7288. Holding potential was −65 mV. B, the plots show the absolute steady-state voltages achieved in response to current pulses delivered in each of the conditions. C, the graph shows the mean (±s.e.m.) amplitude of voltage changes evoked by ZD 7288 (ΔV_ZD) as a function of control steady-state voltage (V_i) in 5 MNCs. Note the strong inward rectification at negative voltages and that application of ZD 7288 has no effect on V_i at potentials ≤−60 mV.