NS9283 mimics the effects of neostigmine but only at high concentrations. NS9283 at 10 μm prolongs the decay (τ₂, C) and increases the amplitude (a₂, D) of the EPSC. Increasing the concentration to 50 μm induces a further slowing of the decay τ₂ but not a further increase of the amplitude of the slow component. A, B, 1p-EPSC (A) and 5p-EPSC (B) in control, with 10 μm NS9283 and 50 μm NS9283. C, D, Time course of the changes of τ₂^1p (C, open circles), τ₂^5p (C, filled circles), and a₂^1p (D, open diamonds) after addition of NS9283 at 10 μm and at 50 μm. E, F, Bar graphs comparing the changes of τ₂^1p and a₂^1p induced by NS9283 10 and 50 μm. The values plotted are the ratio of the values measured under NS9283 and those measured in control conditions. ***p < 0.001.