GluA1 synaptic membrane retention is increased in upscaled Ppt1^−/− neurons. A, Representative image of a SEP-GluA1 transfected, upscaled neuron (top) and a 20-µm segment of dendrite before, immediately after, and 10 min after bleaching of an individual spine (arrow, bottom). Scale bar = 20 µm for low-magnification images, 10 µm for high-magnification images. B, Time-dependent recovery of SEP-GluA1 fluorescence after photobleaching (FRAP) in WT and Ppt1^−/− primary cortical neurons. Five-six spines were bleached for each cell and averaged for to make one n. Trace represents average of n = 5 cells across 2 independent cultures. C, Nonlinear fit of (single phase decay) of SEP-GluA1 fluorescence after photobleaching (FRAP) in upscaled WT and Ppt1^−/− primary cortical neurons. Comparison of nonlinear fits: F_(3,220) = 542.9, ****p < 0.0001. n = 5 cells across 2 independent cultures. D, Quantification of the immobile fraction (percent unrecovered compared with prebleach fluorescence) of SEP-GluA1 fluorescence after photobleaching (FRAP) for each cell. t test: *p = 0.0356. n = 5 cells across 2 independent cultures, 5–6 spines/cell. Data represent mean ± SEM.