Figure 2

Carbachol-induced GIRK currents in adult mouse ventricular myocytes. (a) Whole-cell currents (V_hold = −70 mV) evoked by carbachol (CCh, 100 μM) in a high-K⁺ bath solution (containing 5 μM BaCl₂) in adult ventricular myocytes from wild-type, Girk1^−/−, Girk4^−/−, and Rgs6^−/− mice. Scale: 0.1 nA/10 s. (b) Summary of maximal CCh-induced current density in adult ventricular myocytes from wild-type (n = 28 cells/6 mice), Girk1^−/− (n = 23 cells/4 mice), Girk4^−/− (n = 21 cells/4 mice), and Rgs6^−/− mice (n = 24 cells/6 mice); open symbols overlapping the bars denote individual data points. One-way ANOVA analysis revealed an effect of genotype on CCh-induced current density (F_3,92 = 110.6, P < 0.001). Symbols: **^, ***P < 0.01 and 0.001, respectively, vs. wild-type. (c,d) Summary of activation (c; t₄₄ = 0.7, P = 0.51) and deactivation (d); t₄₄ = 1.1, P = 0.28) kinetics for the CCh-induced current in ventricular myocytes from wild-type (n = 25 cells/6 mice) and Rgs6^−/− mice (n = 21 cells/6 mice), compared across genotypes using an unpaired Student’s t-test. (e) Summary of EC₅₀ values derived from concentration-response experiments for the CCh-induced current in adult ventricular myocytes from wild-type vs. Rgs6^−/− mice. The EC₅₀ for current activation by CCh did not differ between wild-type (4.8 ± 0.6 μM, n = 11 cells/4 mice) and Rgs6^−/− (4.9 ± 0.4 μM, n = 19 cells/4 mice) ventricular myocytes, as determined using an unpaired Student’s t-test (t₂₈ = 0.20, P = 0.84).