Nav1.1 immunosignals in forebrain excitatory neurons are reduced in Scn1afl/fl, Emx1-Cre mice. (A and B) Representative parasagittal sections of P21.5 Scn1afl/fl (A) and Scn1afl/fl, Emx1-Cre (B) hippocampi stained with anti-Nav1.1 antibody. Higher magnification images outlined in (a) are shown in (b). Scale bars: (a) 400 µm; (b) 40 µm. DG, dentate gyrus; o, stratum oriens; p, stratum pyramidale; l, stratum lucidum. (C and D) Representative parasagittal sections of P21.5 Scn1afl/fl (C) and Scn1afl/fl, Emx1-Cre (D) neocortices, stained with anti-Nav1.1 antibody. Higher magnification images outlined in (a) are shown in (b). Scale bars: (a) 400 µm; (b) 40 µm. Arrows indicate Nav1.1-immunoreactive neurites oriented toward the pial surface, which putatively correspond to AISs of neocortical PV cells (,) (see also Fig. O). Double arrowheads indicate Nav1.1-immunoreactive proximal neurites oriented toward the ventricular surface in neocortical layer V. (E–H) Representative parasagittal sections of 8-week-old Scn1afl/fl (E) and Scn1afl/fl, Emx1-Cre (F) hippocampi, and 8-week-old Scn1afl/fl (G) and Scn1afl/fl, Emx1-Cre (H) neocortices, stained with anti-Nav1.1 antibody. Higher magnification images outlined in (a) are shown in (b). Scale bars: (a) 400 µm; (b) 40 µm. Arrowheads indicate the Nav1.1-immunoreactive bands extending from the stratum lacunosum-moleculare within the CA fields to the molecular layer of dentate gyrus, which virtually correspond to the hippocampal perforant path. DG, dentate gyrus; o, stratum oriens; p, stratum pyramidale; l, stratum lucidum; r, stratum radiatum; lm, stratum lacunosum-moleculare; m, dentate gyrus molecular layer; g, dentate gyrus granule cell layer. (I and J) Representative coronal sections of 8-week-old Scn1afl/fl (I) and Scn1afl/fl, Emx1-Cre (J) brains stained with anti-Nav1.1 antibody (n = 3 per genotype). Arrowheads and arrows indicate the Nav1.1-immunoreactive bands, which correspond to hippocampal perforant path and corpus callosum, respectively. Higher magnification images outlined in (a) are shown in (b). Note that reductions in Nav1.1 immunostaining intensities in the medial perforant pathway, corpus callosum and neocortical layers II/III, V and VI in Scn1afl/fl, Emx1-Cre mice were observed in comparison with Scn1afl/fl controls. CC, corpus callosum; DG, dentate gyrus; S1BF, primary somatosensory cortex, barrel field. Scale bars: 100 µm. Nuclear immunosignals are non-specific (). Parasagittal images are oriented from the pial surface (top) to the callosal (bottom), and from rostral (left) to caudal (right). Coronal images are oriented from lateral (left) to medial (right). fl, floxed allele.