Fig. 2.

Cs⁺ blockade of Ca²⁺ influx through HCN4 channels in HEK293 cells. (A) Ca²⁺ signals in response to hyperpolarizing pulses in the absence and presence of 2 mM CsCl. Two of the pulse-induced Ca²⁺ signals are analyzed below. Similar results were observed in all three cells tested. The dashed lines are baselines. (B) Fd signals corresponding to arrows a and b in A. (C) I_HCN4 (trace a) was blocked by 2 mM Cs⁺ (trace b). Dashed line represents zero current. (Lower) The voltage protocol is shown.