GRIK1 and epilepsy: Thus, while most of genes coding for glutamate receptor subunits increased their expression in epilepsy (GRIA1, GRIA3, GRIA4, GRIK3, GRIK4, GRIK5, GRIN2B, GRIN3A, GRM1, GRM7, and GRM8), few were downregulated (GRIA2, GRIA3, GRIN2A, GRM5, GRIK1, and GRIK2) (Fig. 4b, c).