Confocal microscope images of activated microglial cells MHC II (green OX-6 positive) in the Dentate Gyrus. Rats infused with aCSF (A) had only a few activated microglia scattered throughout the brain. Chronic infusion of LPS into the 4th ventricle produced high activated microglia distributed throughout the hippocampus (B). Higher magnifications of an activated microglia (C, D) show the characteristic contracted and ramified processes with bushy morphology. Cell nuclei are stained red (ToPro3). Scale bars: (A-B) 100 μm; (C) 25 μm; (D) 2.5 μm.