Fig. 4. Aβ^pH is phagocytosed by cortical microglia and astrocytes in vivo and by rat retinal microglia in vivo. (A) Schematic of stereotaxic microinjection of Aβ^pH in the somatosensory cortex of P7 mouse followed by staining of fixed tissue section after 24 and 72 hours. (B) Phagocytic uptake of Aβ^pH by IBA1⁺ microglia and GFAP⁺ astrocytes in the periventricular white matter at the 24 hour timepoint. The box represents the region of the fluorescence image where high magnification confocal imaging was done. (C) IBA1⁺ microglia show bright green fluorescence at 72 hours in the same region indicating presence of Aβ^pH within the cells at this timepoint. GFAP⁺ astrocytes do not show any green fluorescence in this region at this timepoint suggesting either degradation of the peptide or insufficient Aβ^pH concentration for detectable phagocytic uptake by these cells. (D) Quantification of Aβ^pH fluorescence within IBA1⁺ microglia and GFAP⁺ astrocytes located in the pia and white matter regions show more Aβ^pH uptake by microglia compared to astrocytes. (E) Schematic of subretinal injection of Aβ^pH to evaluate its in vivo uptake by rat retinal microglia and astrocytes. (F) IBA1⁺ rat retinal microglia phagocytose Aβ^pHin vivo. (G) Quantification of Aβ^pH uptake into retinal IBA1⁺ microglia and GFAP⁺ astrocytes. No fluorescence was detected in astrocytes at these 3 time points (n.d.). Data shown as mean ± s.e.m. from 2 animals.