Subcellular distribution of NL1 and GluA1 surface accumulation following somatic ER release. (A) Images of DHFR-GFP-NL1 (top) and DHFR-GFP-GluA1 (bottom) surface accumulation at the soma (left), proximal dendrites (middle), and distal dendrites (right) before and 90 min following somatic ER release in the presence of TTX or Bic. Merged images show the Alexa647-anti-GFP signal (magenta) and the cell fill (green). White arrowheads indicate spines with detectable levels of surface signal. Scale bars, 5 µm (somatic images); 2 µm (dendritic images). (B) Time course of the fraction of spines in proximal (circles) and distal (triangles) dendrites that contain surface NL1 (gray) or GluA1 (black) following somatic ER release in the presence of TTX. A comparison of the fraction of NL1- and GluA1-positive spines at 90 min and 120 min is shown on the right; mean ± SEM; *, P < 0.05; **, P < 0.01 (unpaired t test; n = 5 neurons [NL1], n = 7 neurons [GluA1] from at least two independent experiments). (C) Time course of the fraction of spines in proximal (circles) and distal (triangles) dendrites that contain surface NL1 (gray) or GluA1 (black) following somatic ER release in the presence of Bic. A comparison of the fraction of NL1- and GluA1-positive spines at 90 min and 120 min is shown on the right; mean ± SEM; *, P < 0.05; ***, P < 0.001 (unpaired t test; n = 5 neurons [NL1], n = 8 neurons [GluA1] from at least two independent experiments). dist., distal; prox., proximal.