Figure 6. Effects of serotonin on miniature EPSCs.

Left, effects of 5-HT in original recordings on 2 different time scales. The events were recorded at −60 mV in the presence of 5 μm TTX and 5 μm bicuculline. The spontaneous synaptic currents were recorded on video tape at 36 kHz digitization rate and subsequently filtered at 3 kHz with an eight-pole Bessel filter, redigitized at 8–10 kHz and then analysed using an event detection program (see Methods). The amplitude distributions were compared by using a Kolmogorov-Smirnov test. Right, corresponding frequency histograms of miniature EPSC amplitude before and after bath application of 50 μm 5-HT for a short period of 5 min. Serotonin clearly reduced the frequency (number of the events) of the spontaneous miniature EPSCs, while the mean amplitude was not significantly changed (from -26.8 ± 0.4 to -27.7 ± 0.6 pA). When analysing the amplitude distribution with a cumulative probability (insets), a small shift to the right (bigger amplitudes) could be observed, but these changes were not significant (Kolmogorov-Smirnov test, P= 0.5). The histograms were plotted with a bin width of 1.6 pA and were composed of 668 events under control, 209 events with serotonin and 418 events after washout.