The TRPM4 non-selective cation channel contributes to the mammalian atrial action potential

► The TRPM4 inhibitor 9-phenanthrol reduces action potential duration in mouse atrium. ► The non-specific TRPM4 inhibitor flufenamic acid reduces action potential in atrium. ► TRPM4 gene disruption reduces action potential duration in mouse atrium. ► The non-selective cation channel TRPM4 participates in the atrial action potential.