Figure 8. A GABA_B receptor antagonist completely blocks CCK-8S-induced synaptic depression.

A, a time–effect plot of a representative cell showing that CCK-8S reversibly depresses evoked EPSC (a–c). In the same cell, following washout of CCK-8S, application of CGP55845 (1 μm) causes an enhancement in the evoked EPSC amplitude (d). At the peak of this effect, CCK-8S no longer causes a depression in the EPSC amplitude (e). Above this graph are sample synaptic responses taken from the times indicated by the letters in the time–effect plot. Note that traces b and e, both taken in the presence of CCK-8S are associated with an inward current (displacement from dashed line). B, normalized average plot (n= 5 cells) showing the effect of CGP55845 on EPSC amplitude and subsequent lack of effect of CCK-8S in the presence of CGP55845. C, summary bar graph comparing the effect of CCK-8S in control (from Fig. 2) and in the presence of 1 μm CGP55845.