ApoE peptide (EP) affects tau kinases in primary neurons. Cultured primary neurons were treated with buffer or EP, a tandem repeat of the receptor-binding domain of apoE. Panel A: Cells were treated with control buffer ("C") or EP at 2 uM for 2 hours (left panels) or 100 nM overnight (right panels). Cell lysates (20 ug/lane) were electrophoresed and immunoblotted for phospho-GSK 3β (P-GSK 3β), total GSK 3β, P35, CDK5 and β-actin. β-Actin was measured from the same blots to ensure that equal protein was present in every lane. Panel B: Quantification of these blots revealed a significant decrease (*P < .05) in levels of P-GSK 3β(4 fold decrease), P35 (3.5 fold decrease), and CDK5 (5 fold decrease) with 2uM EP treatment. However, no significant decreases were noted with 100nM EP treatment. Histographs show mean +/- standard error, n = 4.