Fig. 4

Schematic drawings indicate the injection site of each tracer and levels of the frontal sections shown on the right panels. In all the frontal sections shown in A-L, the lateral side of the brain is to the left. (A–F) PGl receiving tectal inputs. (A and B) DiI retrograde labeling (magenta), showing the injection site in the PGl (A; asterisk), and a retrogradely labeled neuron (B; arrow) located in a deep layer (SPV) of the optic tectum (TeO). This neuron extends its dendrites (B; arrowheads) to the upper layer (SFGS) where retinal projections terminate. (C and D) BDA anterograde labeling (brown) showing the injection site in TeO (C; asterisk) and anterogradely labeled terminals in the ipsilateral PGl (D; arrowheads). (E) Cresyl violet staining showing the cytoarchitecture of the zebrafish PG: the lateral (PGl) and the anterior (PGa) subdivisions can be identified, based on the comparison with the goldfish PG (the nomenclature applied from goldfish; Yamamoto and Ito, 2008). (F) GFP+ labeling in the PG of Tg(279A-GFP) zebrafish line (20 µm projection of confocal images; GFP in green and DAPI in grey), showing a section comparable to the level shown in (E). GFP+ perikarya are mostly found in PGl. (G–L) PGl neurons projecting to Dl of the pallium. (G and H) Biocytin injection site in the PGl (G; asterisk) and anterogradely labeled terminals in the ipsilateral Dl (H). The right top inset in (H) shows a higher magnification of the squared area showing numerous labeled terminals. (I) GFP+ fiber labeling in the Dl of Tg(279A-GFP) zebrafish line, demonstrating an arborization pattern comparable to the anterograde biocytin labeling shown in (H). (J and K) Biocytin injection site in the Dl (J; asterisk), and retrogradely labeled neurons in the ipsilateral PGl (K) that extend dendrites ramifying in the neuropil. (L) GFP+ perikarya labeling in the PGl of Tg(279A-GFP) zebrafish line (arrowheads; 5 µm projection), demonstrating the almost identical cell localization as shown in (K). Abbreviations: Dl, lateral part of dorsal telencephalic area; PGa, anterior preglomerular nucleus; PGl, lateral preglomerular nucleus; SAC, stratum album centrale; SFGS, stratum fibrosum et griseum superficiale; SGC, stratum griseum centrale; SPV, stratum periventriculare; TeO, optic tectum. Brain orientation: r, rostral; c, caudal; d, dorsal; v, ventral. Scale bars = 50 µm (A, D-G, K, and L); 20 µm (B); 200 µm (C); 100 µm (H–J).