SCN1A and Dravet syndrome: We crossed VGAT-ChR2 mice with knock-out Scn1a+/– mice, which model the epileptic encephalopathy Dravet syndrome and in which one allele of the Scn1a gene is not functional, causing NaV1.1 haploinsufficiency and hypoexcitability of GABAergic neurons (17, 21).