Chronic BCNU administration decreases amyloid plaque burden in mice. APdE9 mice were treated daily by intraperitoneal injections with BCNU starting from four months to six months of age for 60 days. Amyloid plaques were stained by thioflavin S in coronal brain sections. A) A representative section with amyloid plaques in vehicle-treated mice at six months of age is shown. B) A representative section of brain showing decreased amyloid plaques in mice treated with BCNU is shown. C) Quantitation by ImageJ analysis showed decreased plaque burden by 81% (P < 0.01) when compared to vehicle-treated APdE9 mice. D) The total number of plaques was reduced by 26% (P < 0.05). E) Plaques measuring more than 1.0 square micron were reduced by 39% (P < 0.05). F) Plaques measuring more than 3.0 square microns decreased by 41% (P < 0.05). In each group, n = 6, ± SEM. *, P < 0.05, **, P < 0.01 in BCNU-treated APdE9 mice versus vehicle-treated APdE9 mice by student's t test. BCNU, 1, 3 bis (2-chloroethyl)-1-nitrosourea; SEM, standard error of the mean.