PS protects NMDA-treated mouse neurons via activation of PI3K/Akt antiapoptotic pathway. A, PS dose-dependently (5–200 nm) mediates Akt phosphorylation (pAkt, Ser473) in mouse cortical neurons 1 h after NMDA. Graph, pAkt relative abundance normalized to total Akt. *p < 0.05, PS compared with untreated NMDA controls. B, Akt phosphorylation (pAkt, Ser473) in mouse cortical neurons 1–24 h after NMDA with and without PS. Graph, pAkt signal normalized by total Akt. C, Akt activity determined by a GSK-3α/β phosphorylation-based assay 1 h after NMDA in the absence and presence of PS. pAkt and total Akt levels were determined by immunoblotting analysis from the same samples used in Akt activity assay. Graph, Relative abundance of pGSK-3α/β normalized by total Akt. D, Akt phosphorylation (pAkt, Ser 473) and total Akt levels in mouse cortical neurons 24 h after NMDA with or without PS or the PI3K inhibitor LY294002 (50 μm). E, Survival of mouse cortical neurons 24 h after NMDA with and without PS in the presence and absence of LY294002 (50 μm) or U0126 (10 μm). LY294002 and U0126 were added to the culture 30 min before NMDA treatment. F, Akt kinase activity in neurons transduced with kinase-deficient Ad.Akt^K179A mutant or control Ad.GFP determined 1 h after NMDA with and without PS by using a GSK-3α/β phosphorylation-based Akt activity assay. Graph, Relative abundance of pGSK-3α/β normalized by total Akt. pAkt and total Akt levels are also shown. G, Survival of DIV7 and DIV21 mouse cortical neurons transduced with Ad.Akt^K179A mutant or control Ad.GFP 24 h after NMDA with and without PS. Values are mean ± SEM from three to six independent cultures. In all studies, DIV7 cortical neurons and murine PS at 100 nm were used unless otherwise specified.