Mediates the voltage-dependent sodium ion permeability of excitable membranes. Assuming opened or closed conformations in response to the voltage difference across the membrane, the protein forms a sodium-selective channel through which Na(+) ions may pass in accordance with their electrochemical gradient. Plays a key role in brain, probably by regulating the moment when neurotransmitters are released in neurons. Involved in sensory perception of mechanical pain: activation in somatosensory neurons induces pain without neurogenic inflammation and produces hypersensitivity to mechanical, but not thermal stimuli. Inactivation of this channel is specifically inhibited by the spider toxins Hm1a and Hm1b (H.maculata, AC P60992 and AC P0DOC5) in somatosensory neurons to elicit acute pain and mechanical allodynia. The voltage-sensitive sodium channel consists of an ion conducting pore forming alpha-subunit regulated by one or more beta-1 (SCN1B), beta-2 (SCN2B), beta-3 (SCN3B) and/or beta-4 (SCN4B). Beta-1 (SCN1B) and beta-3 (SCN3B) are non-covalently associated with alpha, while beta-2 (SCN2B) and beta-4 (SCN4B) are covalently linked by disulfide bonds. Interacts with FGF13 (PubMed:21566136). Interacts with SCN1B (PubMed:17928445, PubMed:15525788). Interacts with the conotoxin GVIIJ (PubMed:24497506). Interacts with the spider beta/delta-theraphotoxin-Pre1a (PubMed:28428547). The sequence contains 4 internal repeats, each with 5 hydrophobic segments (S1, S2, S3, S5, S6) and one positively charged segment (S4). Segments S4 are probably the voltage-sensors and are characterized by a series of positively charged amino acids at every third position. The S3b-S4 and S1-S2 loops of repeat IV are targeted by H.maculata toxins Hm1a and Hm1b, leading to inhibit fast inactivation of Nav1.1/SCN1A. Selectivity for H.maculata toxins Hm1a and Hm1b depends on S1-S2 loops of repeat IV. Phosphorylation at Ser-1516 by PKC in a highly conserved cytoplasmic loop slows inactivation of the sodium channel and reduces peak sodium currents. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. SCN1A mutations may be involved in Panayiotopoulos syndrome, a benign age-related focal seizure disorder occurring in early and mid-childhood. It is characterized by seizures, often prolonged, with predominantly autonomic symptoms, and by an electroencephalogram that shows shifting and/or multiple foci, often with occipital predominance. Autonomic seizures in Panayiotopoulos syndrome consist of episodes of disturbed autonomic function with emesis as the predominant symptom. Cardiorespiratory arrest is exceptional. Belongs to the sodium channel (TC 1.A.1.10) family. Nav1.1/SCN1A subfamily.