CME is required for NMDAR–LTD but not for basal synaptic transmission or synaptic downscaling. A, Treatment with dynasore does not affect basal excitatory synaptic transmission. Time course of EPSC amplitude evoked at 0.2 Hz at Schaffer collateral–CA1 synapses after infusion of control (n = 6), 100 μm dynasore (Ds; n = 8), vehicle (Veh, 0.1% DMSO; n = 6), or 50 μm QVPSRPNRAP (DIP; n = 6) by inclusion in the intracellular solution. B, The pairing protocol effectively induces LTD with control intracellular solution (Control; n = 12) but intracellular infusion of dynasore (n = 9) inhibits LTD in the test pathway. Right, Representative current traces from time points shown (1, black: 1 min before pairing; 2, gray: 25 min after pairing). C, Application of 50 μm myristoylated DIP (myrDIP) blocks AMPAR internalization in the live-labeling assay. Control, Vehicle-treated samples. n = 3. D, Overexpression of the Dyn2–K44A construct does not affect homeostatic downscaling. Hippocampal neurons (12–14 d in vitro) transfected with Dyn2wt–GFP or Dyn2K44A–GFP were treated with 15 mm KCl and 40 μm bicuculline for 48 h (Scaled) and labeled to quantify sGluA1 and sGluA2. Control, Dyn2wt-expressing cells under control conditions. n = 3. Scale bar, 20 μm.