In hippocampal culture, Ser133 CREB phosphorylation after KCl-depolarization is not blocked by the NMDA antagonist MK 801. (A) Pretreatment of primary hippocampal cultures with the NMDA antagonist, MK 801 (1 μM) did not block CREB phosphorylation induced by KCl-depolarization (20 mM or 90 mM). Levels of CREB protein were unchanged. (B) Pretreatment of primary hippocampal cultures with nifedipine (20 μM) blocked KCl-depolarization-mediated CREB phosphorylation (20 mM). Levels of CREB protein were unchanged. All data are shown in duplicate. (C,D) Statistical analysis of the effect of MK 801 on Ser133 CREB phosphorylation by KCl (C) or FPL 64176 (D) shows that MK 801 blocks neither KCl-, nor FPL 64176-mediated Ser133 CREB phosphorylation in primary hippocampal neurons. n=6 samples for each treatment, level of induction normalized to an internal control. Average fold induction±S.E.M.