Figure 3.

The number of synaptically activated APs appears to depend on the size of EPSC, not on postsynaptic spiking properties. A, B, Examples of different AP numbers evoked by the same stimulation paradigm (10 pulses, 333 Hz). Stimulation times are shown as dots. The synaptic current in A did not produce a background current and elicited only one AP. When synaptic currents induced a strong background current, multiple APs were elicited (B). In any case, depression of EPSC amplitudes was severe (D). C, All cells, similar to the depicted example, followed with APs to 1 ms current injections up to 500 Hz. The inset shows last AP of the train. D, EPSCs depress during a 10 pulse stimulation paradigm in a frequency-dependent manner.