Histochemical analysis of GCs was performed as described previously (Couillard-Despres et al., 2006 (link)). Cells were filled with biocytin (2 mg ml−1) during whole-cell recording (see below) and stored afterwards at room temperature for at least 1 hr. Acute brain slices were fixed overnight in 4% paraformaldehyde and then incubated for 24 hr with 0.3% triton X-100 (Sigma-Aldrich) together with FITC-conjugated avidin-D (2 µl ml−1, Vector, RRID:AB_2336455 ) at 4°C to visualize biocytin filling. After washing, the slices were embedded in Prolong Gold (Molecular Probes). Fluorescence labeling was analyzed with a confocal laser scanning microscope (LSM 700, Zeiss) using a 40x oil-immersion objective (NA 1.4) acquiring 1 µm-thick optical sections.
The morphology of the dendritic trees of biocytin-filled young and mature granule cells was analysed after generating maximum intensity projections from confocal stacks covering the full size of neurons using ImageJ. The diameter of the dendritic cone was measured parallel to the GCL, either at the base corresponding to the widest part (dendritic cone diameter) or at 100 µm distance from the soma (diameter at 100 µm). The maximal extension of the dendritic tree corresponding to the height of the cone was measured from the soma towards cone base in approximately radial direction from the GCL.
The morphology of the dendritic trees of biocytin-filled young and mature granule cells was analysed after generating maximum intensity projections from confocal stacks covering the full size of neurons using ImageJ. The diameter of the dendritic cone was measured parallel to the GCL, either at the base corresponding to the widest part (dendritic cone diameter) or at 100 µm distance from the soma (diameter at 100 µm). The maximal extension of the dendritic tree corresponding to the height of the cone was measured from the soma towards cone base in approximately radial direction from the GCL.