Fig. 2

Histamine-induced microglial phagocytosis of PS particles/residues. a Bar graph displays the stimulatory effect of 100 μM histamine (H100) on the phagocytosis of phosphatidylserine (PS)-conjugated liposomes in vitro. Specific effect on PS-induced phagocytosis was ruled out by using annexin V (AnxV). Data are expressed as mean ± SEM (n = 2–10) and as a percentage of control. *P < 0.05, using one-way ANOVA followed by Bonferroni’s multiple comparison test. Right panel: representative photomicrographs illustrate the stimulatory effect of 100 μM histamine on microglial phagocytosis of PS liposomes in vitro. PS liposomes: red labeling; CD11b: green labeling; nuclei (Hoechst 33342): blue. Scale bar 10 μm. b The bar graph represents the volume of CD11b+ cells containing PS liposomes in SN slices from mice injected intracranially with 100 μM histamine for 18 h. Data are expressed as mean ± SEM (n = 4–6 mice) and as a percentage of saline. *P < 0.05, using an unpaired t test as compared with saline mice. Right panel: representative photomicrographs illustrate the stimulatory effect of histamine on microglial phagocytosis of PS liposomes in vivo. PS liposomes: red labeling; CD11b: green labeling; nuclei (Hoechst 33342): blue. Arrows highlight co-labeling events. Scale bar 10 μm. c Representative confocal photomicrographs showing that the stereotaxic injection with 100 μM histamine (H100) in the SN of adult mice for 3 days induced co-localization (highlighted with white arrows) between PS residues (green), CD11b labeling (red), and TH dopaminergic neuronal staining (white). This co-localization was less evident in saline animals. Cell nuclei were stained with Hoechst 33342 (in blue). Scale bar 10 μm