PP2A activity in HT-22 cells following treatment with glutamate and/or 17β-estradiol in the presence of specific inhibitors of PP1, PP2A, or calcineurin. HT-22 cells were seeded in 100 mm dishes at a density of 250,000 cells/ml. (A) Cells were treated simultaneously with 100 nM okadaic acid, 10 mM glutamate, and/or 10 μM 17β-estradiol. (B) Cells were treated simultaneously with 200 nM PPI2, 10 mM glutamate, and/or 10 μM 17β-estradiol. (C) Cells were treated simultaneously with 9 μM endothall, 10 mM glutamate, and/or 10 μM 17β-estradiol. (D) Cells were treated simultaneously with 500 nM CsA, 10 mM glutamate, and/or 10 μM 17β-estradiol. PP2A activity was determined using a serine/threonine phosphatase activity assay (Promega, Madison, WI) after 24 h exposure to the various compounds. All data were normalized to % survival of vehicle treated control. Depicted are mean ± SEM for six independent experiments with triplicates per experiment. *P < 0.05 vs. glutamate treated group.