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Fig. 4
GFP+ vENT neurons and habenular innervation in Tg(lhx5:GFP)b1205 transgenic zebrafish. Images are transverse sections (A,B,D-F,H), lateral view (C) or parasagittal section (G) of adult zebrafish wild type (A,B,E,E′) or Tg(lhx5:GFP)b1205 (C-D′,F-H) brains. (A,B) Nissl stained sections showing the cytoarchitecture of the vENT (arrows in A and B) and dENT at anterior (same level as shown in schematic Figure 2C) and posterior (same level as shown in schematic Figure 2D). By following serial sections it can be noted that only the vENT extends into caudal areas of the telencephalon (arrow in B). (C) Lateral view of intact brain from a Tg(lhx5:GFP)b1205 fish (anterior to the left) showing GFP+ cells in the vENT (arrow), among other structures and areas. Note that vENT cells form a band extending from the level of the anterior commissure (ac) into the telencephalic peduncule (indicated with a star). (D) GFP+ cells in the vENT (arrow), but not in the dENT, of a Tg(lhx5:GFP)b1205 fish. (D′) Dense neuropil of GFP+ fibers in the habenula of a Tg(lhx5:GFP)b1205 fish. Dotted lines mark the habenulae. (E) NPY+ cells in the dENT and fibers (arrowheads) in the medial area of the pallium (Dm; arrow). (E′) Very few NPY+ fibers are found in the habenulae. Note that some of the labeling observed in the image is caused by autofluorescence of blood vessels. (F,G) Double immunohistochemistry against NPY and GFP in transverse (F) and parasagittal (G; anterior to the left) sections of a brain from a Tg(lhx5:GFP)b1205 fish. Note that NPY+ cells are restricted to the dENT (arrowheads). GFP+ cells were observed in the vENT (arrows). Note in (G) that the dENT (arrowheads) does not extend as far caudal as the vENT (arrows) and there is a clear gap (star) between the two nuclei. Bundles of axons from the lateral forebrain bundle (lfb) travel through both nuclei. (H) Retrogradely DiI labeled cells (arrows) in the vENT of a Tg(lhx5:GFP)b1205 fish after tracer application to the habenula. Scale bars: 150 µm in (A,B,D-E′); 250 µm in (C); 100 µm in (F,G) and 50 µm in (H).