(A) A schematic representation of synaptic inputs onto the basal and apical dendrites of CA1 pyramidal cells and the positioning of electrodes. In slices from naive and VHCT mice, electrical stimulation was applied at the stratum oriens [Stim.(SO)] or stratum radiatum [Stim.(SR)] of area CA1. Whole-cell recordings [Rec.(WC)] were made from CA1 pyramidal cells. Basal and Apical represent recordings from basal and apical synapses, respectively. Sch, schaffer collateral fibers; Com, commissural fibers. (B to F) Inhibitory effects of Ro 25-6981 on NMDA EPSCs from CA1 pyramidal neurons. Sample superimposed traces indicate NMDA EPSCs recorded in the absence (Control) and presence of Ro 25-6981 (Ro, 0.6 µM). The levels of inhibition were maximal after exposure to Ro 25-6981 for 50 to 60 min. Left and Right indicate recordings from left and right hippocampal slices, respectively. Each trace is the average of five consecutive recordings. Scale bars, 25 pA (vertical) and 100 ms (horizontal). Relative amplitudes of NMDA EPSCs in the presence of Ro 25-6981 are expressed as percentages of control responses. Error bars represent s.e.m. (n = 7 each, *P<0.01, absence of an asterisk indicates P>0.05).