The role of RhoA in Aβ induced neuron death. (A, B) Hippocampal neurons (30,000 cells/cm2) were cultured for 7 days and then treated with Aβ (5 μM). Two days later the neurons were transfected with the dn RhoA N19 and on the following day, the cells were stained and the number of live cells were determined as described in the Methods. (A) Representative micrographs of double-labelled cultured hippocampal neurons under the four conditions described. Green represents EGFP immunostaining, red is the transfected myc-tagged RhoA N19 and the DAPI stained nuclei are blue. (B) Quantification of live cells. Note that transfection with the dominant negative form of RhoA rescued a significant number of neurons from Aβ-induced death. (C) The effects of Anti-amyloid were more dramatic when C3 ADP ribosyl transferase (1 μM), a RhoA inhibitor, was applied to the cultures. Cultured hippocampal neurons (7 DIV) were treated simultaneously with C3 ADP ribosyl transferase and Aβ, and the number of live cells was determined four days later in culture.