Figure 2

Expression of HCN subunits in the hippocampus at P0 and P7. (A-1): At P0, the expression of HCN1 was strong in the alveus and so, sp, sl, and sr of the CA, and in the GCL of the dentate gyrus (DG). (E-1): HCN2 expression at P0 was observed in the alveus, sp, sl, and sr of the CA, and in the GCL of the DG. (I-1): HCN4 showed a similar pattern of expression to HCN1 at P0. Note that migrating cells (yellow arrows) from the ventricular zone (vz, white arrows) expressed all HCN isoforms, but the expression of HCN1 and HCN2 subunits was more prominent than that of HCN4. At P7, immunolabeling for HCN1 (A-2), HCN2 (E-2), and HCN4 (I-2) was observed in the sp and slm of the CA, and in the gcl of the DG. HCN1 (B, C, D) and HCN2 (F, G, H) subunits were expressed in neuronal somata, but not in astrocytes. Labeling for HCN4 was observed in the slm, as well as in the border of the slm with the molecular layer (ml) of the DG. (B, F, J): Double immunofluorescence with GFAP showed that most GFAP-positive astrocytes were also immunolabeled with HCN4 in the slm, and in the border of the ml in the DG. B, C, D: yellow arrows indicate HCN1 labeling, white arrows indicate GFAP labeling. F, G, H: yellow arrows indicate HCN2 labeling. J, K, L: white arrow indicates an astrocyte double-labeled for HCN4 and GFAP. Abbreviations: GCL (or gcl), granule cell layer; sl, stratum lucidum; slm, stratum lacunosum moleculare; so, stratum oriens; sp, stratum pyramidale; sr, stratum radiatum. Scale bars = 20 μm.