Objective To investigate the mRNA expression level of the HCN channel subtypes in sinoatrial node of adult SD rats with volume-overloaded heart failure as well as the effects of bisoprolol on this process and heart rate.Methods Healthy male SD two-month-old rats were selected to establish the abdominal ateriovenous fistula as a left-to-right shunt model in order to induce volume-overload heart failure;sham operated rats served as controls.After the rats were fed together for 2 months,they were randomly admi...