Choline induced upregulation of NMDAR-dependent LTP of mEPSCs in cultured hippocampal neurons. (A) Examples of continuous recordings from individual neurons 5 minutes before (Basal) and 30 minutes after 8-minute stimulation of neurons with 1 mM choline. (B) Single events taken from the basal and choline traces, respectively showing that the amplitude of mEPSCs was increased by choline application. (C) Cumulative fraction plots for mEPSCs inter-event intervals and amplitudes obtained 5 minutes before (Basal) and 30 minutes after choline (8 min, 1 mM). (D) mEPSC amplitudes are normalized to the values from the initial 10 min and plotted over time. Treatment of neurons with choline (8 min, 1 mM) significantly increased the amplitude of the mEPSCs over the time course of recordings; an effect can be abolished by NMDAR antagonist, AP5 (100 μM). (E) Amplitude histogram summarizes data from groups of individual neurons treated with glycine (200 μM; 3 min) in the absence or presence of choline (1 mM) or choline/AP5 (100 μM). Responses obtained 30 min after glycine treatment (26.5+/- 2.3 pA), 30 min after choline treatment (31.4 +/-2.7 pA, n = 6, *p < 0.01) and 30 minutes after coapplication of choline/APV (25.9+/-2.0pA n = 3, **p < 0.05, paired t-test).