Caspase inhibitors DEVD- and LEHD-FMK block LTD in CA1 hippocampal neurons. Acute hippocampal slices (from 3–4 week old rats) were incubated with caspase inhibitors for 2 hr before recording (DEVD-FMK, 2 µM; LEHD-FMK, 2 µM; FA-FMK, 10 µM; YVAD-FMK, 5 µM). Extracellular field EPSPs were evoked by stimulating Schaffer collateral – CA1 synapses. (A and B) Effect of DEVD-FMK on LTD and LTP, induced by low frequency stimulation (LFS) and tetanic stimulation (Tet) respectively (control, n=6; DEVD-FMK, n=6). (C and D) Effect of LEHD-FMK on LTD and LTP (n=6). (E and F) Effect of YVAD-FMK or negative control peptide FA-FMK on LTD and LTP (n=6). Pooled data and example traces are shown in all panels. Symbols and error bars indicate mean ± SEM. See also Figure S1.