Figure 8. P_r-independent modulation of latency at DG–CA3 synapse.

A, scheme shows experimental configuration. A CA3 pyramidal cell was recorded in voltage clamp in the whole-cell configuration of the patch-clamp technique, and a train of 25 mossy fibre EPSCs was evoked by stimulating a granular cell of the dentate gyrus in organotypic hippocampal slices. Bottom, example of short-term facilitation of the mossy fibre synapse stimulated at 20 Hz. B, plot of EPSC latencies vs. normalized amplitude for pooled data (n= 12). Note that amplitude-dependent latency variation (fitted by a logarithmic curve in orange; y=−1.4ln(x) + 12.5, r²= 0.92) was only present for the first EPSCs, whereas the last EPSCs diverge from this law (red arrow). Inset, amplitude-dependent latency distribution in the presence of 4-AP (40 μm) is fitted by a logarithmic curve (y=−0.8ln(x) + 14.1, r²= 0.75). C, summary of the latency stabilization during repetitive stimulation at the mossy fibre–CA3 cell synapse. From stimulation 1 to 5, latency decreases because of enhanced P_r (orange traces and arrowhead), whereas latency increases from stimulation 5 to 25 because of AP broadening (red traces and arrowhead). Abbreviations: Mfb, mossy fibre bouton; and Pyr, CA3 pyramidal cell.