Fig. 1. F-actin levels are increased in hippocampal neurons treated with A. (A) Control hippocampal neurons grown on poly-D-lysine for 4 days were stimulated with 10 µM of fibrillar A_1-42 for 4 hours and double stained for Tub-Tyr (green) and F-actin filaments with Rhodamine-phalloidin. Overlay of Tub-Tyr with phalloidin is shown. Scale bar, 20 µm. (B) Hippocampal cells, untreated or stimulated for 4 hours with 10 µM A_1-42 were immunostained with phalloidin-TRITC and the F-actin intensity was analyzed. The values are expressed as the main ± s.e.m. Data are representative for three different experiments, with at least 12 determinations per experiment (^*P<0.05). (C) F-actin levels in control and 4-hour and 24-hour A-stimulated neurons were measured with Actin Polymerization Assay kit. Phalloidin (P) was used as a positive control. The ratio of F-actin/total actin was determined from the blots by densitometric measurements. Significant differences are indicated by asterisks (^*P<0.05, ^***P<0.005; Student's t-test).