Molecular code of the zebrafish amygdaloid complex. Definitions of amygdaloid territories in the complexly everted telencephalon: Amygdala model (basal ganglia (BG) not considered) (A–D) versus idealized topological amygdala model (B’,C’,D’,E,F) indicating tela attachments and radial glia distribution. (A–D) The lateral schematic (A) of the amygdala model divides the zebrafish amygdaloid complex with regard to the anterior commissure (ac) into precommissural (B), supracommissural (C), and postcommissural (D) sectors. A hierarchical code defines all amygdaloid nuclei: All medial extended amygdaloid nuclei in the supra- and postcommissural sectors (C,D) are located within the isl1:GFP negative, subpallial (GABAergic) territories and comprise numerous calretinin-positive neurons. The CeAd is distinguished from such MeA-territories through the presence of parvalbumin-fibers and cells that are laterally displaced. More anterior lying CeA-territories such as the CeAa, CeAl also form part of the isl1:GFP negative subpallium, they are, however, distinguished from the CeAd through their lack of parvalbumin expression. In addition, all dopaminergic clusters formerly viewed to the zebrafish striatopallidum are here considered the anterior (BSTa) and posterior (BSTp) divisions of the bed nucleus of the stria terminalis (BST). These dopaminergic extended amygdaloid nuclei are also located in the zebrafish isl1:GFP free territory that corresponds to the mammalian dLGE (= Vdd). The medial BST(m) is the only subpallial amygdaloid territory where a large population of isl1:GFP forms the majority of this nucleus in addition to some calretinin-positive neurons that link this nucleus with the rest of the extended medial amygdala. The newly discovered integrative olfactory nucleus (IOP) shows secondary olfactory projections and many parvalbumin positive neurons. In contrast, the amygdaloid nLOT that also receives secondary olfactory projections lacks these parvalbumin neurons. (E) Topological amygdala model indicating idealized BG relationships showing tela attachment sites and radial glia distribution as revealed in this study.
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