Fig. 3. Syntaxin 13 is not enriched at mature synapses. Embryonic hippocampal neurons 11 DIV were fixed and stained for syntaxin 13 (A, D, G) and SV2a (B, E, H); the respective merged images are shown in C, F, and I, with areas of overlap inyellow. A–C, Portion of an axon running along a dendrite. Note that mature synapses, marked by the SV2a staining, do not show enrichment of syntaxin 13. D–F, Isolated immature axon that does not contact any dendrites. The SV2a staining likely represents mobile clusters of synaptic vesicles.G–I, Giant axon. J–L, Giant axon of embryonic hippocampal neuron 11 DIV that was loaded first with 10 mg/ml HRP–biotin for 30 min and then was fixed and stained for syntaxin 13 (J). HRP–biotin was detected by using streptavidin–TxR (K); L shows the merged image, with areas of overlap in yellow. Scale bars: A–C, 1 μm; D–I, 2 μm;J–L, 10 μm.