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In the published paper of Bérubé-Carrière et al. (2012), the scale bars of Figures 2–5 were presented with an error, indicating ‘1 mm’ instead of ‘1 μm’. The correct scale bars are indicated here.

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Figure 2.  DA terminals from the NAC in P15 or adult control and Vglut2 cKO mice. As illustrated in this and the following figures, the TH-immunolabeled terminals (varicosities) in NAC (Figs 2 and 5) and NAS (Fig. 3), as well as in NS (Fig. 4), share similar ultrastructural features, whether in control or Vglut2 cKO mice of both ages (see also Tables 1 and 2). These varicosities are relatively small, generally round or ovoid in shape, filled with small vesicles and associated or not with mitochondria, and the vast majority are without apparent synaptic membrane specialization (junctional complex). (A, C and D) Rare examples of TH-labeled synaptic varicosities, most of which form small, symmetrical junctions (between small arrows) with dendritic branches (db). (B, E and E′) More typical examples of asynaptic terminals. In B, the labeled varicosity is seen emerging from its parent thin unmyelinated axon (open arrow), and it is directly apposed to several other unlabeled varicosities (av). E and E′ are two sections across the same labeled terminal, neither of which displays a synapticmembrane specialization. A and D are from Vglut2f/+;DAT-cre and Vglut2f/f controls, respectively, whereas C is from a cKO (Mtl) and B, E and E′ from cKO (Upp) mice. Tissue primarily fixed by perfusion of acrolein. Scale bar (in E′), 1 μm.

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Figure 3.  DA terminals from the NAS in P15 or adult control and Vglut2 cKO mice. These electron micrographs from the NAS (control or Vglut2 cKO, Mtl) further illustrate ultrastructural characteristics of mesostriatal DA terminals in the mouse. (A) Two varicosities, along the same axon, are juxtaposed with a dendritic branch (db), with which the upper one forms a relatively wide symmetrical synapse (between small arrows). (B–F) All labeled terminals appear to be asynaptic. In A, B, C, and E, intervaricose axon segments are designated by open arrows. In D, the varicosity appears to be larger than average and its parent axon (open arrow) contains small vesicles in its narrow as well as dilated portion. Tissue primarily fixed by perfusion of acrolein. Scale bar (in F), 1 μm.

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Figure 4.  DA terminals from the neostriatum in P15 or adult control and Vglut2 cKO mice. (A) The TH-labeled varicosity is truly exceptional, as it displays not only one but two synaptic junctions (between small arrows) made with distinct dendritic branches (db). The synapse on the right is on the neck of a spine (sp) which arises from the upper dendritic branch. This spine is contacted synaptically on its head by another axon varicosity (av), unlabeled. (C) Rare occurrence of a labeled varicosity in synaptic contact (between small arrows) with a dendritic spine (sp). In this case, the junction looks rather asymmetrical. Note that this synaptic labeled varicosity is itself juxtaposed with another labeled varicosity profile, which is not entirely uncommon. (B, D, E and F) Representatives of the large majority of asynaptic labeled terminals. In B, the presence of three varicosity profiles within the same field reflects the high density of innervation. In E, the two elongated profiles presumably belong to the same axon, again illustrating the very short interval between such varicosities. F is another example of a relatively large TH-labeled varicosity. A, E and D are from Vglut2f/+;DAT-cre and Vglut2f/f controls, respectively, whereas B is from a cKO (Mtl) and C and F from cKO mice. Tissue primarily fixed by perfusion of acrolein. Scale bar (in F), 1 μm.

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Figure 5.  DA terminals from the core of nucleus accumbens in adult wild-type mice fixed by perfusion with a glutaraldehyde–paraformaldehyde mixture. There was no apparent difference in the ultrastructural features of TH-labeled varicosities from these mice, by comparison with those from control and cKO mice perfused with acrolein as primary fixative (see Results for morphometric data). (A and A′) Two sections across the same labeled varicosity, which forms a relatively wide symmetrical synaptic contact (between small arrows) with a dendritic branch (db). (B) Two labeled varicosity profiles appear more typically asynaptic. Scale bar (in B), 1 μm.

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