Excess extracellular acetylcholinesterase (AChE) decreases glutamatergic synaptic activities. A. Representative traces of miniature excitatory postsynaptic currents (mEPSCs) recorded at the 11th day in vitro in neurons grown in control medium (A-1) and in synaptic AChE (AChE-S)-conditioned medium with 10 μM physostigmine (A-2). B. Cumulative distribution of the amplitude (B-1) and interval (B-2) of mEPSCs recorded in a neuron cultured in control medium (Ctrl) and in a neuron grown in AChE-S-conditioned medium with physostigmine (AChE). C. Amplitude (C-1) and frequency (C-2) of mEPSCs recorded in a group of neurons cultured in control medium (Ctrl) and in neurons grown in AChE-S-conditioned medium with physostigmine (AChE). Amplitude under control conditions: 25.5 ± 2.5 pA, n = 6 cells; amplitude under high-AChE conditions: 20 ± 2 pA, n = 8 cells; frequency under control conditions: 1.04 ± 0.15 Hz, n = 6 cells; frequency under high-AChE conditions: 0.32 ± 0.14 Hz, n = 8 cells. * P < 0.05, ** P < 0.001.