Figure 12.

Subcortically projecting neurons can be driven to fire persistently with spike trains. A, CPn neurons are driven to fire 5, 10, or 15 action potentials with 1 ms, 20 Hz trains of depolarizing current from either −65 or −60 mV. In the presence of 20 μm CCh, these trains are sufficient to cause CPn neurons to persistently fire. B, COM neurons cannot be driven to fire persistently in the presence of CCh even with 50 APs delivered in the same manner. C, Counts of COM (red) and CPn (green) neurons that fire persistently using trains of spikes. D, E, In both COM (light red, inset) and CPn (light green, inset) neurons, a 1 nA, 10 ms depolarizing current injection does result in a small (0–1.5 mV) ADP. With the addition of 20 μm CCh, most COM neurons (4 of 5) exhibit a slight increase in the ADP (dark red, inset). In 1 of 5 COM neurons, a large ADP occurred with CCh (arrow). In CPn neurons (dark green, inset), a much larger ADP is elicited in the presence of CCh.