The influence of M₂R-I_KACh signaling on in vivo HR and HRV.

<p>Summary of baseline and post-CCh (300nM CCh) in-vivo HR (A) and HRV (B) in WT, <i>Rgs6</i>^<i>-/-</i>, and <i>Girk4</i>^<i>-/-</i> mice. (‘*’ denotes statistical significance of p < 0.05 between baseline and CCh within the same genotype. ‘&’ denotes a statistically significant (p < 0.05) difference for both baseline and CCh when comparing between two genotypes). ‘#’ denotes statistical significance of p < 0.05 between WT and <i>Rgs6</i>^<i>-/-</i> mice post-CCh. ‘$’ denotes statistical significance of p < 0.05 between <i>Girk4</i>^<i>-/-</i> and <i>Rgs6</i>^<i>-/-</i> mice post-CCh. Statistics performed using 1-way ANOVA.) (C) Quantification of the total number of mice that exhibited arrhythmias post CCh. (‘*’ denotes statistical significance of p < 0.05 between <i>Girk4</i>^<i>-/-</i> and <i>Rgs6</i>^<i>-/-</i>. Statistics performed using Fisher’s exact test). (D) Representative examples of ECG data during control and demonstrating episodes of arrhythmia in WT and <i>Rgs6</i>^<i>-/-</i>, and no arrhythmia in <i>Girk4</i>^<i>-/-</i> mice post CCh. n = 8, 8, 6 for WT, <i>Rgs6</i>^<i>-/</i>-, and <i>Girk4</i>^<i>-/-</i>_, respectively.