(a) Time-lapse images of DIV 13 primary hippocampal neurons co-transfected with DsRed (to visualize cellular morphology) and SEP-tagged GluN2 constructs. Cells were exposed to 200 μM NMDA and imaged for 25 min. Arrows depict structural hallmarks of excitotoxic effects (dendritic varicosities and cell body swelling) in neurons expressing DsRed alone, GluN2A, or GluN2B. GluN2C-expressing neuron images show resistance to NMDA-induced toxicity. Scale bar, 10 μm. (b) Quantitiative summary of data showing the average number of dendritic varicosities per 10 μm length of dendrite (Vector, n = 18 dendritic segments, 6 cells; GluN2A, n = 18 dendritic segments, 6 cells; GluN2B, n = 21 dendritic segments, 7 cells; GluN2C, n = 24 dendritic segments, 8 cells, *p < 0.05, ***p < 0.01, One-way ANOVA and Bonferroni test). (c) Time-lapse images of zoomed in dendritic regions of hippocampal neurons co-expressing DsRed and SEP-tagged GluN2A, GluN2B, or GluN2C (green) before (0 min) and following administration of 200 μM NMDA. Scale bar, 2 μm. (d) Time course distribution of receptor enrichment for spines and dendritic segments from hippocampal neurons treated with NMDA (SEP-GluN2A, n = 24 spines, 6 dendritic segments, 4 cells; SEP-GluN2B, n = 31 spines, 7 dendritic segmens, 4 cells; SEP-GluN2C, n = 20 spines, 11 dendritic segments, 7 cells, *p < 0.05, One-way ANOVA and Bonferroni test).