Interactions of protein O-GlcNAcylation with NMDAR-dependent LTP and LTD. A1, Decrementing LTP occurs when HFS is delivered immediately following a 10 min GlcN application (n = 7 with 100 μm GlcN; n = 6 without GlcN). A2, Decreased LTP magnitude following 1 h treatment with TMG (1 μm, n = 6 with TMG; n = 6 without TMG). A3, O-GlcNAc LTD is reversible using HFS to induce LTP (n = 6). B1, Simultaneous LFS and GlcN application (100 μm, 15 min, n = 5) does not induce greater LTD than LFS alone (n = 5). B2, Saturation of NMDAR-dependent LTD occludes O-GlcNAc LTD (n = 3). B3, Saturation of O-GlcNAc LTD does not occlude further LTD induced by LFS (n = 4). *p < 0.05, **p < 0.001, and ***p < 0.0001. Error bars indicate SEM. Calibration: 0.4 mV, 10 ms.