The following antibodies were used: PAK1 (Zymed Laboratories), PAK3 (Stressgen Biotechnologies), total PAK (PAK 1,2 and 3, Cell Signaling Technology), anti-b-actin (Chemicon International), antibody to NSE (Research Diagnostics), anti-pPAKserine 141 and anti-oligomer A11 (Biosource International), antibodies to PAKThr423 (Cell Signaling), cofilin (BD Transduction Labs), drebrin (clone M2F6, MBL), synaptophysin (MAB368, Chemicon International), Neurofilament (SMI312, Sternberger Monoclonals) and antibody to pMBP (Upstate Biotechnology). Affinity purified antibody to fractin and anti-Ab (10G4) rabbit polyclonal antibodies were developed and characterized in our laboratory.