The number of activated microglia is reduced in both the hippocampus and motor cortex in BCNU-treated mouse brains. A) Iba1 positive activated microglia (red) in the CA3 region of the hippocampus shown in saline- or BCNU-treated mouse brains. The nuclei were stained with DAPI (blue) and the merged images (yellow) show microglia positive for Iba1, which were counted. B) Iba1 positive activated microglia in the motor cortex. The magnification and the scale bars are indicated. The inset in both A and B is to show an enlarged microglia positive for both DAPI and Iba1. C) Quantification showed 30% (P < 0.05) and 44% (P < 0.01) reduced numbers of activated microglia in the hippocampus and motor cortex, respectively. All values are mean ± SEM, n = 5 in each group. *, P < 0.05, **, P < 0.01 in BCNU-treated APdE9 mice versus saline-treated APdE9 mice by student's t test. BCNU, 1, 3 bis (2-chloroethyl)-1-nitrosourea; DAPI, 4',6-diamidino-2-phenylindole; SEM, standard error of the mean.