Figure 6. A facilitating connection onto a regular spiking CA1 interneurone (soma in proximal stratum oriens) exhibiting reduced facilitation at short interspike intervals.

Following all first EPSPs (A) and following first spike failures (B), second EPSPs at the shortest intervals are less facilitated than at slightly longer intervals. With these summing EPSPs the peak amplitude attained during the train is independent of frequency or of first/second EPSP amplitude. Release-dependent depression may thus be limiting peak responses. Facilitation with release-dependent and release-independent depression would therefore explain these data.