(A) Akt inhibitor IV normalizes the suppressed LTD induced by LFS (1 Hz, 15 minutes) at hippocampal SC-CA1 synapses in Ngl3−/−(Hyb) mice (P16–20). n = 8 slices from three mice for WT-V, 8, 3 for WT-D, 8, 3 for KO-V, and 7, 3 for KO-D; **P < 0.01, ***P < 0.001, ns, not significant, two-way ANOVA with Bonferroni test. (B) DCS has no effect on LTP induced by HFS (100 Hz, 1 second) at hippocampal SC-CA1 synapses of Ngl3−/−(Hyb) mice (P26–32). n = 9 slices from three mice for WT-V, WT-D, KO-V, and KO-D; **P < 0.01, ns, not significant, two-way ANOVA with Bonferroni test. (C) DCS has no effect on LTD induced by LFS (1 Hz, 15 minutes) at hippocampal SC-CA1 synapses of Ngl3−/−(Hyb) mice (P16–20). n = 7 slices from six mice for WT-V, 7, 4 for WT-D, 6, 5 for KO-V, and 6, 4 for KO-D; ***P < 0.001, ns, not significant, two-way ANOVA with Bonferroni test. Primary data can be found in S3 Data. DCS, D-cycloserine; fEPSP, field excitatory postsynaptic potential; HFS, high-frequency stimulation; KO-D, knockout, drug; KO-V, knockout, vehicle; LFS, low-frequency stimulation; LTD, long-term depression; LTP, long-term potentiation; NMDAR, NMDA receptor; ns, not significant; P, postnatal day; SC-CA1, Schaffer collateral-CA1 pyramidal; WT-D, wild-type, drug; WT-V, wild-type, vehicle.