All S1PRs (S1P1-3) in heart are stimulated using S1P which leads to activation of (Gi, Gq and G12/13) but only S1P1 and S1P3 receptors are activated using FTY720, which leads to activation of Gi.30,31 Thus, the underlying mechanism of bradycardia is due to the activation of inwardly rectifying Gà1-protein-regualted potassium channel (GIRK/IKACh) channels in atrial myocytes and endothelial cells). Here, GNAI1 is linked to Bradycardia.