Figure 3.

PTP of Mossy Fiber Unitary EPSCs Is Primarily Generated by an Increase in the Size of the RRP

(A) EPSCs evoked by a test train of 10 stimuli at 50 Hz (black), EPSCs during HFS_100APs (blue), and EPSCs evoked by a test train of 10 stimuli at 50 Hz 20 s after HFS_100APs (red).

(B) Plot of average EPSC peak amplitude (top) and postsynaptic series resistance (bottom) against experimental time. The red line represents an exponential function fit to the data points, and gray line represents running average. The vertical dashed line indicates time point of HFS_100APs. Data are from 12 pairs.

(C) Summary of the paired-pulse ratio (EPSC₂/EPSC₁) before (black) and after HFS_100APs (red). Note that the ratio was only slightly reduced after HFS_100APs (p = 0.158).

(D) Cumulative EPSC peak amplitude during a train with 10 stimuli at 50 Hz before (black) and 20 s after application of HFS_100APs (red). Data points during the last 3–5 stimuli (at time points ≥ 100–140 ms) were fit by linear regression. Note that PTP markedly increased the size of the RRP (represented by the intersection of the regression line with the ordinate).

(E–G) Summary bar graphs of RRP (E), P_r (F), and refilling rate (G) estimated by the 10-AP paradigm before (black) and 20 s after HFS_100APs (red). Bars represent mean values, error bars indicate SEM, and circles show data from individual experiments; data points from the same experiment are connected by lines. Note that PTP is caused by a preferential increase in RRP.

(H) Plot of RRP against experimental time.