Fig. 4

The activation curves of I_HCN in 5.4 mM [K⁺]_o and 3 mM [K⁺]_o bathing solution. aI_HCN recorded in the 5.4 mM [K⁺]_o solution; I_K1 was suppressed by 1 mM Ba²⁺. bI_HCN in the 3 mM [K⁺]_o solution. The I_HCN was recorded in the same HCN2-Tg mouse myocytes as those mentioned in a. The pulse protocol is indicated below the traces. c The activation curves of I_HCN in the 5.4 mM [K⁺]_o solution (filled black circles) and in 3 mM [K⁺]_o solution (filled red circles). The V_1/2 (membrane potential for half-maximal activation) was − 118.5 ± 2.9 mV (in the 5.4 mM [K⁺]_o solution) and − 117.7 ± 3.4 mV (in the 3 mM [K⁺]_o solution) (n  = 6) (color figure online)