Figure 7.
EPSP-spike coupling in FS interneurons and pyramidal cells in dopamine (DA). (A and B) Upper traces: averaged EPSPs of 20 trials from P-NPFS and P-P connections in control conditions. Lower traces: sample traces showing that spikes were always initiated from the location of EPSPs in a typical FS interneuron during dopamine application, whereas, in pyramidal neurons, spikes were often evoked after the peak of EPSPs. The threshold holding potential was very different between interneurons and pyramidal cells. In interneuron, dopamine was able to induce firing directly by small depolarization, whereas, in pyramidal cell, membrane potential must be held to its threshold level to elicit firing. (C and D) Spike latency histograms constructed from 50 trials of three interneurons in P-NPFS connections and three pyramidal cells in P-P pairs, showing the different variability of initiated spikes in two kinds of postsynaptic neurons (latency average, 12.7 ± 4.07 ms in interneuron and 102.2 ± 8.61 ms in pyramidal cells, P < 0.0001).