NMDA-induced Chem-LTD dephosphorylates CPEB. A, Control slices treated with vehicle (DMSO; 0.01%) for 3 min had modest rundown, whereas slices treated with NMDA (25 μm) for 3 min showed prolonged depression between 40 and 70 min after washout (t = 66 min; control fEPSP slope, 0.90 ± 0.3, n = 6; NMDA fEPSP slope, 0.74 ± 0.4, n = 12; p < 0.05). The bar indicates when NMDA was applied. B, Representative Western blots of hippocampal slices probed with phospho-CPEB and total CPEB treated with either vehicle or NMDA. Three minutes of NMDA treatment (n = 5; ***p < 0.001) significantly decreased CPEB phosphorylation with a slow recovery back to baseline levels at 20 min (n = 5) and 60 min (n = 7) after drug treatment.