Maximal LTP, presynaptic transmitter release and LTD are normal in synpo−/− mice. A, Time course of LTP induced by repeated trains of Schaffer collateral HFS (100 Hz/4 pulse × 10 bursts; arrows) applied each 10 min in field CA1 of slices from 15-d-old synpo−/− (filled triangles, n = 12) and wild-type control mice (filled circles, n = 10). Each point is mean ± SEM of n slices. B, C, Vesicular release from presynaptic Schaffer collateral-CA1 terminals is normal in synpo−/− mice. B, Representative pseudocolor two-photon excitation fluorescent image of RRP puncta in stratum radiatum of field CA1 in a control slice. C, Time courses of Schaffer collateral stimulus-evoked (solid bar; 10 Hz/2 s bursts each 30 s) FM1-43 destaining from the RRP vesicle pool in hippocampal slices from synpo−/− mice (open circles; n = 4 slices) versus wild-type controls (filled circles; n = 4). D, E, Time course of LFS train (2 Hz/10 min; solid bar) induced LTD in field CA1. E, 15-d-old synpo−/− (filled triangles, n = 10) versus wild-type mice (filled circles, n = 9). F, Twenty-one-day-old synpo−/− (filled triangles, n = 9) versus wild-type mice (filled circles, n = 8). Each point is mean ± SEM of n slices.