Enables sodium ion binding activity and voltage-gated sodium channel activity. Involved in neuronal action potential. Located in plasma membrane. Part of voltage-gated sodium channel complex. Is integral component of presynaptic membrane. Human ortholog(s) of this gene implicated in Dravet syndrome; developmental and epileptic encephalopathy; familial hemiplegic migraine 3; generalized epilepsy with febrile seizures plus; and generalized epilepsy with febrile seizures plus 2. Orthologous to human SCN1A (sodium voltage-gated channel alpha subunit 1). [provided by Alliance of Genome Resources, Apr 2022]