Photomicrographs showing changes in microglial activation in the substantia nigra. Activated microglial cells at central levels of the substantia nigra stained with (A, B, E-H) isolectin B4 or (C, D) immunostained for CD45 and higher magnification. Photomicrographs show microglia in WT mice treated with vehicle (controls; A, C), with MPTP alone (B, D), with MPTP + telmisartan (E), or with MPTP + telmisartan + GW9662 (G). Microglial activation in AT1a-null mice (AT1a-/-) treated with MPTP alone or MPTP + GW9662 is shown in F and H, respectively. Microglial activation was significantly higher in mice treated with MPTP alone (B, D), and in mice treated with the neurotoxin, AT1 inhibition and GW9662 (G, H). Scale bar: 100 μm.