PSD-95 and stargazin have differential effects on synaptic and surface AMPAR number. (*A*) Confocal image of a pyramidal cell expressing PSD-95 GFP showing its localization to synaptic spines. (Scale bar: 5 μm.) (*B*) Averaged EPSCs recorded simultaneously from a pair of cells, showing the responses at −70 mV and +40 mV for a PSD-95-transfected cell and a neighboring untransfected (control) cell. (Scale bars: 10 pA, 20 ms.) (*C*) Bar graph representations of data from the PSD-95 transfections. AMPAR EPSCs are significantly enhanced (*P* < 1 × 10^{−6}, *n* = 27 pairs), whereas NMDAR EPSCs are unchanged (*P* = 0.81, *n* = 23 pairs). (*D*) Confocal image of a cell expressing stargazin-GFP shows that it also localizes to synaptic spines (same scale as *A*). (*E* and *F*) Overexpression of stargazin has no effect on evoked synaptic responses (AMPAR EPSCs, *n* = 26 pairs, *P* = 0.48; NMDAR EPSCs, *n* = 14 pairs, *P* = 0.99). (*G*) PSD-95-expressing cells do not show a change in the response to bath-applied AMPA (1 μM, *n* = 3 pairs). (*H*) Overexpression of stargazin dramatically increases responses to bath application of AMPA (500 nM, *n* = 7 pairs, *P* = 0.003).

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