Astrocytes in organotypic hippocampal slice cultures. (a) Organotypic slice cultures at 20 days in culture (d.i.c.). Preparations were derived from animals in which GFP was expressed under control of the GFAP promoter. Shown is the expression of GFP (left), the labeling pattern of SR101 (center), and the corresponding merged image (GFAP: green, SR101: magenta). Asterisks point out SR101-labeled cells that do not express GFP; arrowheads point out GFP-positive, but SR101-negative cells. Images represent maximum intensity projections of 15 optical sections taken at 1 μm intervals. (b) SR101 fluorescence of an organotypic slice at 21 d.i.c. Image represents a stack of 20 optical sections taken at 1 μm intervals. (c) Immunohistochemical double staining for GFAP and S100β as well as DAPI fluorescence and merged image of the fluorescence of GFAP (green) and S100β (magenta) of part of the CA1 region encompassing the strata pyramidale and radiatum of an organotypic slice at 20 d.i.c. Note the radially oriented GFAP-positive fibers crossing the pyramidal cell layer. Images were taken at a wide-field microscope. ((a)–(c)): Dashed lines indicate the approximate boundaries of the stratum pyramidale. StrO, stratum oriens; StrP, stratum pyramidale; StrR, stratum radiatum; StrLM, stratum lacunosum moleculare; and StrM, stratum moleculare. Scale bars: (a) 50 μm, (b) 100 μm, and (c) 50 μm.