Figure 4

Paired-pulse facilitation. A. Paired pulses (PP1 and PP2) were delivered at a 100 msec interval in the absence (saline, black traces) and the presence of DA, 1 μM (gray traces). In this experiment, DA produced a dramatic inhibition to 17% of control, which was accompanied by about a 3-fold increase in the paired-pulse ratio (PPR), from 0.47 to 1.34. Traces shown are the averages of 5 traces. B. Plotting PPR vs. DA inhibition (expressed as the percent of the preceding control IPSC) for all paired-pulse experiments (n = 8), showed that PPR increased with DA modulation, indicative of presynaptic action. The gray-filled circle, corresponds to the experiment shown in panel A.