Effects of ryanodine and Ran on APs of SANs in the control and HF groups. (A) Representative APs of control SANs prior to and after treatment with ryanodine (0.3 and 3 µM). (B) Average SAN beating rates, APA, MDP and DDR prior to and after treatment with ryanodine (0.3 and 3 µM) in the control group (n=6). (C) Representative APs of HF SANs prior to and after treatment with ryanodine (0.3 and 3 µM). (D) Average SAN beating rates, APA, MDP and DDR prior to and after treatment with ryanodine (0.3 and 3 µM) in the HF group (n=6). (E) Representative APs of control SANs prior to and after treatment with Ran (10 µM). (F) Average SAN beating rates, APA, MDP and DDR prior to and after treatment with Ran (10 µM) infusion in the control group (n=6). (G) Representative APs of HF SANs prior to and after treatment with Ran (10 µM). (H) Average SAN beating rates, APA, MDP and DDR prior to and after treatment with Ran (10 µM) in the HF group (n=6). *P<0.05 vs. baseline (0.03% dimethyl sulfoxide) of ryanodine. AP, action potential; APA, AP amplitude; HF, heart failure; SAN, sinoatrial node; MDP, maximum diastolic potential; DDR, diastolic depolarization rate; Ran, ranolazine.