Values represent means ± s.d. of three experiments carried out in triplicate. Hippocampal neurons were pretreated with Wnt-3a ligand with or without heparin for 1 h previous to the addition of 5 mM Aβ1–40. Neurons were then incubated for 24 h and MTT reduction was determined. * Indicates P < 0.05 compared with respect to Aβ + Wnt-3a in a "T" test analyzed by the Sigma plot 2.0 program.