I_inst and I_h flow through the ciHCNb pore in approximately the same proportion.

<p>A. Current traces elicited by a hyperpolarization of the membrane potential from a holding potential of −10 mV to −70 mV before (black trace) or after (gray trace) a 15 min incubation with ZD7288. The complete voltage protocol is shown below the current traces. The dotted line represents the zero current level. B. Bar graph of I_inst and I_h before (black bars) and after (gray bars) 15 minute incubation with ZD7288, as carried out in ‘A’. * indicates a significant block of the current component by this agent (p<0.05 in a two-tailed paired t-test). C. Plot of ZD7288-sensitive I_inst versus I_h. Black line represents a linear correlation, which was a significant (r = 0.9, p<0.05). D. Bar graph showing the ratio of I_inst over total current (I_inst+I_h) that is blocked by Cs+ or ZD7288; this ratio represents the proportion of blocked current that is due to block of I_inst. An example of the Cs+ data used for this figure is shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0047590#pone-0047590-g002" target="_blank">Figure 2</a>. In ‘B’ and ‘D’, values represent mean ± s.e.m and the numbers in brackets are the numbers of oocytes used. The ZD7288 data in ‘B’, ‘C’ and ‘D’ come from the same 9 oocytes.