Fig. 9

Brainstem CD68+ microglial cells exhibit endocytic activity at resting conditions. A A low-magnification photomicrograph of FG fluorescence observed at the brainstem. The animals were killed 3 h after the i.p. FG injection. Note the intense FG signal within the AP illustrating its diffusion from fenestrated capillaries. Scale bar: 500 µm. B Photomicrographs illustrating FG diffusion from surrounding AP structures where CD68+ microglia are present. Lower panel IMARIS bitplane software rendering of confocal Z-stacks was then used to visualize internalized FG within CD68+ microglia. Scale bar: 50 µm. C A representative high magnification confocal photomicrograph of FG signal and CD68+ immunostaining on DVC coronal section. Note the vicinity between CD68+ microglia and the punctiform FG signal. Scale bar: 20 µm. D Magnified photographs of the regions indicated by the box in panel C showing the co-localization of FG dot signal within CD68+ processes of microglia located in the funiculus separans. Arrowheads indicate the presence of FG punctiform signals enclosed in CD68+ processes. Inset IMARIS bitplane images of fluorogold and CD68 co-localization allowing visualization of internalized FG. Lower panel IMARIS bitplane image of co-localization allowing visualization of internalized FG in CD68+ microglia. Scale bar: 5 µm. AP: area postrema; cc: central canal; fs: funiculus separans; NTS: nucleus tractus solitaries; XII: hypoglossal nucleus