Fig. 4.

β₂-, Not β₁-, receptor activation augments I_h. A: example voltage-clamp traces show I_h in control, formoterol (100 nM), and formoterol+ZD7288 (100 μM). B: the ZD7288-sensitive I_h in control and formoterol obtained by subtraction. C: the formoterol-sensitive/enhanced I_h component. D: group data (n = 5 cells) show that formoterol increases the amplitude of the ZD7288-sensitive I_h. E: group data showing the net drug-sensitive I_h in the different conditions (n in parentheses); see text for details.