Figure 9. ZD7288 reduces STP ratios by acting on presynaptic sites, but facilitates fEPSP₁ by acting on postsynaptic cells.

A, voltage steps from −60 mV to −70 ∼−120 mV produced inward currents, in which the slow component, i.e. I_h current, was reduced by extracellular treatment with 30 μm ZD7288 under control conditions (Aa), whereas this effect was occluded when 100 μm ZD7288 was loaded into a patch pipette (Ab). Insets show typical raw traces. B, representative responses to 40-Hz trains without (Ba) or with intracellular ZD7288 (Bb) before (Control) and after extracellular treatment with 30 μm ZD7288. A and B indicate that intracellular loading of ZD7288 selectively blocks postsynaptic I_h activity. C, summary of the effect of extracellular ZD7288 on burst responses. EPSC₁ (grey) and STP ratios (black) were differentially affected by extracellular ZD7288 application. Note that the effect of extracellular ZD7288 (Extra ZD) in the presence of intracellular ZD7288 (Intra ZD) was similar to that obtained by field recordings (see Fig. 8). *P < 0.05, **P < 0.01 versus data without extracellular ZD7288; Tukey's test (n = 6 slices).