LAUSR

The hippocampus in fluoxetine-treated mice responds differently with regard to volume and cell numbers under stressful vs enriched conditions. To account for effects specific to defined septo-temporal segments of the hippocampus, dissected hippocampi were straightened (a) and embedded in an egg-albumin-based matrix (see asterisk in c). Systematically collected sections along the hippocampal septo-temporal axis were assigned and analyzed unambiguously for the septal, middle and temporal third. As an example in b, volumetric measurements in the CA1 molecular layer are only decreased in the septal third in fluoxetine-treated animals under stressful conditions. Representative cross sections of the straightened hippocampus are shown in c: top panel: Giemsa-stained hippocampus used for volumetric measurements of the main hippocampal fields and estimation of the resident granule cell population size. Middle panel: immunohistochemistry visualizes the proliferating, Ki67-positive cells in the subgranular layer of the dentate gyrus (arrow and insert). Lower panel: identification of young, doublecortin (DCX)-positive neurons in the subgranular layer (arrow and insert) can significantly be augmented by applying a light hematoxylin counterstain. The embedding matrix (*) picks up unspecific background stain in the immunohistochemical-treated material (middle and lower panels), but this does not compromise the specificity of the antigen labeling in the tissue itself. Scale bar: 250 μm, inset scale bar: 10 μm. For more information on this topic, please refer to the article by Alboni et al. on pages 552–561.