Enables transmembrane transporter binding activity and voltage-gated sodium channel activity involved in cardiac muscle cell action potential. Involved in SA node cell action potential; positive regulation of heart rate; and regulation of atrial cardiac muscle cell membrane depolarization. Acts upstream of or within cardiac conduction and ventricular cardiac muscle cell action potential. Located in Z disc. Is expressed in several structures, including gut; nervous system; sensory organ; skeletal musculature; and urinary system. Used to study Brugada syndrome 7. Human ortholog(s) of this gene implicated in Brugada syndrome 7. Orthologous to human SCN3B (sodium voltage-gated channel beta subunit 3). [provided by Alliance of Genome Resources, Apr 2022]