(a–d) Representative photomicrographs of hippocampal sections immunostained for the A2A receptor (green) and the astrocyte marker GFAP (red) from nontransgenic (NTG) mice and from transgenic mice expressing hAPP alone (a) or in combination with a mutant form of PS1 (b), transgenic mice expressing a mutant form of human tau (Tau-P301S) (c), or knock-in mice expressing human apoE3 (APOE3-KI) or apoE4 (ApoE4-KI) (d). Ages of the mice are indicated in months (m, left). Cell nuclei were labeled with DAPI (blue). Insets (i–xi) show magnified views of the boxed regions. DGgl: dentate gyrus granular layer. n = 7 NTG and 8 hAPP mice (a); 3 NTG and 5 hAPP/PS1 mice (b); 1 NTG/7 m, 4 Tau-P301S/3 m and 4 Tau-P301S/6.5 m mice (c); 3 APOE3-KI/6 m, 3 APOE3-KI/19 m, 3 APOE4-KI/6 m, and 3 APOE4-KI/17 m mice (d). Scale bars: 50 μm.