In vivo imaging of astrocytes, dendritic spines, and blood vessels using LSCM. Schematic representation of an in vivo brain imaging experiment through a cranial window in a Thy-1 GFP-M mouse after intravital staining of astrocytes with SR101 (A). At 60× magnification, astrocytic somata were clearly identified by intravital staining one hour after SR101 injection in single plane confocal images ~50 μm below the brain surface (B, left panel). GFP-expressing dendrites from layer V pyramidal neurons showed also distinct staining (B, central panel). Astrocytes were bulk loaded employing Fluo-4 AM and thus, also show fluorescence in the 488 channel (B, central and right panel). Large blood vessels project black shadows on the background since they are a major source of light scattering (). Astrocytes were observed projecting branches into the neuropil, contacting dendrites and their spines, and blood vessels through endfeet. Images taken at higher magnification in another area (C) show details of astrocytic somata and processes (C, second panel) contacting dendritic spines (C, third panel) and blood vessels (C, fourth panel). Scale bars: 50 μm in B; 20 μm (first panel) and 5 μm (second to fourth panels) in (C).