NMDAR activation controls accumulation of multiple synaptic vesicle proteins at developing excitatory presynaptic terminals. (A, B) Immunofluorescence images of synaptophysin in a control neuron (A) and a neuron treated with APV to block NMDA receptors (B). Fluorescence intensity is pseudo-colored according to the indicated scale. (C) Higher magnification immunofluorescence images of synaptophysin (arrows) in a GFP-transfected axon (white outline). Left, control neuron; right, neuron treated with APV to block NMDAR activation. Scale bars: 10 μm. (D, E) APV treatment decreased accumulation of synaptophysin at developing presynaptic terminals. Both the intensity (D) and apparent sizes (E) of synaptophysin puncta were decreased upon APV exposure. (F) APV did not change presynaptic terminal density. (G) Blockade of NMDA receptors with APV decreased the expression of VGlut1 at terminals. Data are presented as normalized mean ± standard error of the mean, and the number of puncta (D, E, G) and axons (F) measured are indicated on each bar. *, significant difference (P-values are indicated in the figure).