A, in a representative cell, CCK-8S (1 μm) causes a reversible depression of the evoked EPSC amplitude (a–c). Following washout of CCK-8S and pretreatment of the same cell with proglumide (Prog. 100 μm; d), 1 μm CCK-8S no longer had an effect on the evoked EPSC amplitude (e). Above this graph are sample EPSC traces taken from the times indicated by letters in the time–effect plot. B, normalized average time–effect plot obtained from five cells that were pretreated with Prog (100 μm), a-non-selective CCK receptor antagonist, prior to CCK-8S application. C, a bar graph summarizing the effects of 1 μm CCK-8S alone (from Fig. 2), and in the presence of Prog (100 μm).