(D) Immunofluorescence analysis of young CX3CR1+/GFP and old APPPS1/CX3CR1+/GFP slices freshly cut (0 DIV), cultured alone or in co-culture (10 DIV) and immunostained using GFP (green) shows alterations in microglial morphology of old cells upon culturing. Upper-left panels are enlargements of boxed regions. A GFP antibody was used to amplify the signal of GFP-expressing old microglial cells. Scale bars: 50 µm.(E) Quantitative analysis of amoeboid microglial cells in young CX3CR1+/GFP (white bars) and old APPPS1/CX3CR1+/GFP (green bars) brain slices freshly cut (0 DIV), cultured alone or in co-culture (10 DIV). The values are expressed as percentages of amoeboid microglia from the total number of microglial cells. The values represent mean ± SEM from 3 independent experiments, each experiment including at least 250 cells per condition (*P < 0.05, ***P < 0.001). 