Fig. 4. Rac1 and Cdc42 display enhanced F-actin colocalization in hippocampal cells treated with A. (A) Four-day hippocampal neurons, untreated (control) and exposed to A_1-42 fibrils for 4 hours were double immunostained with Rac1 or Cdc42 and Rhodamine-phalloidin and analyzed by confocal laser-scanning microscopy. Images in the upper panel are overlays of Rac1 or Cdc42 vs. Rhodamine-phalloidin staining. Arrows indicate increased actin protusions in amyloid-stimulated neurons. Lower panels are higher magnification of the boxed regions showing Rac1 and Cdc42 overlaying with F-actin in control conditions, as well as the augmented colocalization of these proteins with F-actin (arrowhead) after A stimulation. Scale bar, 20 µm. (B) Respective scatter plots of fluorescence intensity distribution for Rac1/F-actin and Cdc42/F-actin from control and A-stimulated neurons. (C) Colocalization coefficients between Rac1/F-actin and Cdc42/F-actin were evaluated using Zeiss colocalization coefficient function software. Data are expressed as mean ± s.e.m.