vglut2 and gad expression reveal distinct patterns of dual GABAergic versus glutamatergic cotransmitter phenotypes of dopaminergic and noradrenergic neurons in the zebrafish brain.
Bottom Line: Our results show that most dopaminergic neurons also express GABAergic markers, including the dopaminergic groups of the olfactory bulb (homologous to mammalian A16) and the subpallium, the hypothalamic groups (A12, A14), the prethalamic zona incerta group (A13), the preoptic groups (A15), and the pretectal group.All together, our results demonstrate that all catecholaminergic groups in zebrafish are either GABAergic or glutamatergic.We compare our results with those that have been described for mammalian systems, discuss the phenomenon of transmitter dualism in the context of developmental specification of GABAergic and glutamatergic regions in the brain, and put this phenomenon in an evolutionary perspective.
Affiliation: Developmental Biology, Institute of Biology I, Faculty of Biology, Albert-Ludwigs-University Freiburg, 79104, Freiburg, Germany.Show MeSH
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Mentions: gad1b and gad2 expression has been shown to largely overlap in the developing brain of several model organisms (Ahman et al., 1996; Dupuy and Houser, 1996; Martin et al., 1998). Indeed, a gross comparison of their expression patterns by FISH showed that they are both expressed in a similar manner in major areas of the zebrafish brain at 4 dpf (data not shown). We focused our analysis on the potential colocalization of gad1b/2 with TH immunoreactivity in larval DA clusters, and detected some differences in the distribution of gad1b/2 transcripts in specific nuclei of the brain. Our results are shown in Figure 1, organized from dorsal to ventral (see Fig. 1A, B1, B2 for orientation on the distribution of TH-immunoreactive clusters), and summarized in Table2.
Affiliation: Developmental Biology, Institute of Biology I, Faculty of Biology, Albert-Ludwigs-University Freiburg, 79104, Freiburg, Germany.