The interaction between bacterial lipopolysaccharide (LPS) and HCN channels could contribute to the disturbed beating rate regulation in severe sepsis. To consider the impact of this interaction on the functional level, the influence of LPS, the HCN channel inhibitor ivabradine and the calcium channel inhibitors nifedipine and verapamil on the beating rate of spontaneously contracting cardiomyocytes in vitro was studied. The concentrations of intracellular cAMP and interleukin-6 were determined. LPS caused a significant reduction in beating rate. By adding LPS to ivabradine treated cells, the beating rate could not be reduced further. In contrast, the co-incubation of cardiomyocytes with LPS and calcium channel inhibitors led to an additive beating rate reduction. The results indicate a specific interaction of LPS with HCN channels that is not mediated by a change in the concentrations of intracellular cAMP or interleukin-6.