CACNA1D and Sinus bradycardia: Conclusion: Genetic ablation of cardiac IKACh in mice prevents exercise-induced sinus bradycardia by suppressing training induced remodeling of inward currents If, ICaT and ICaL due in part to the prevention of miR-mediated transcriptional remodeling of HCN4 and likely post transcriptional remodeling of Cav1.3.