Fig. 1
Dopamine (DA) decreased evoked excitatory postsynaptic current (eEPSC) amplitude. A: Inhibitory effect of DA on eEPSC amplitude. Left: Application of 10 μM DA markedly decreased the eEPSC amplitude (red traces). The averaged traces (black trace: baseline for 2 min; red trace: after 5–7 min DA application) were scaled to the amplitude of the first EPSC and superimposed for comparison. This result suggests that the DA-induced inhibitory effect involves a presynaptic mechanism. Right: Time course of changes in eEPSC amplitude induced by 10 μM DA in deep cerebellar nuclei neurons. B: Increase in paired-pulse ratio (PPR) during DA application. A paired-pulse protocol with a 50-ms interval was applied. PPRs were recorded before (baseline) and 5–7 min after 10-μM DA application (DA). A significant increase in PPR was observed after DA application. Each column represents the mean ± SEM. C: Variance analysis of eEPSC in DCN neurons. The ratio of CV–2 was plotted against the ratio of the mean eEPSC amplitude (n = 11). Both CV–2 and the mean eEPSC amplitude were determined by using 10 sweeps before and during the application of 10 μM DA. The filled circle represents means ± SEM. D: Concentration–response curve for DA-induced inhibition. The extent of eEPSC inhibition at different DA concentrations was plotted, representing the effects observed 5–7 min after DA application. Data are the least-mean square fit to a concentration–response curve with the Hill coefficient. Each point represents the mean ± SEM. The numbers adjacent to each point indicate the number of experiments.
