At birth (P0), GIRK3 was expressed intensely in the principal cells of all hippocampal areas, whereas very weak labelling was detected in the dendritic layers (Fig. 4C1). At P5, the distribution pattern of GIRK3 changed dramatically, showing a decrease in the pyramidal cell layer and strong expression in the neuropil of all dendritic layers, with the strongest labelling seen in the stratum lucidum in the CA3 region (Fig. 4C2). A similar pattern, albeit with greater intensity, of GIRK3 immunolabelling was observed during the second (P10) and third (P5) postnatal week compared with P5 (Fig. 4C3 and C4). However, at P15, intense GIRK3 labelling was also observed in the inner third of the molecular layer in the dentate gyrus (Fig. 4C4). At P21, GIRK3 immunolabelling was observed in the neuropil of all dendritic layers, with the strongest intensity occurring in the stratum lucidum in the CA3 region and stratum lacunosum–moleculare of the CA1 region (Fig. 4C5). At P60, the distribution of GIRK3 immunolabelling was of similar intensity throughout the neuropil of all dendritic layers in the CA1 region, CA3 region and
