Catecholaminergic systems in the zebrafish. IV. Organization and projection pattern of dopaminergic neurons in the diencephalon

Abstract

In the diencephalons of the adult zebrafish brain, all catecholamine-containing neurons are dopaminergic. The organization and projection pattern of these neurons are studied using tyrosine hydroxylase immunocytochemistry. By their locations, 3 neuronal complexes and 17 cell groups are identified on the bases of their morphology, staining intensity, and projection pattern: 1) the preoptic complex (5 groups); 2) the posterior tuberal complex (4 groups); and 3) the hypothalamic complex (5 groups). In addition, three other groups can be distinguished: one group in the ventral thalamus; one in the pretectal area, and one found in the postoptic commissure and above the pituitary stalk in a few brains. Two dopaminergic pathways are defined: 1) the preoptico-hypophyseal tract runs in close association with the lateral forebrain bundle along the base of the brain between the preoptic area and the pituitary stalk, and neurons of the preoptic complex are major contributors to this pathway; additional fibers come from the large periventricular organ-associated neurons of the posterior tuberal; 2) the endohypothalamic tract links neurons of the hypothalamic complex and consists mainly of processes from hypothalamic neurons. Axons from neurons of the suprachiasmatic, periventricular organ-associated, and posterior tuberal nuclei also join this pathways after entering the hypothalamus. Several groups of neurons contact the cerebrospinal fluid. These appear to be primarily local neurons because none have processes that join the two major pathways. The preoptic area, dorsal thalamus, tuberal and hypothalamic areas, optic tectum, and pituitary are the major targets of diencephalic dopaminergic neurons. The dorsal telencephalon does not receive input from these cells. The large periventricular organ-accompanying neurons have descending projections beyond the diencephalon and isthmus. Some cells of this group terminate in the crista cerebellaris. A few axons also exit the medulla via a branch of the octavolateralis nerve.

Transgenic zebrafish that express tyrosine hydroxylase promoter in inner retinal cells

“…The distribution of catecholamines that was determined by transgene expression in this study seemed to be broader than the distribution of catecholamines determined using other methods, e.g., immunocytochemistry and in situ hybridization (Ma, 1994a(Ma, ,b, 1997(Ma, , 2003Guo et al, 1999a;Holzschuh et al, 2001;Rink and Wullimann, 2002;Ma and Lopez, 2003). In developing zebrafish, only a few groups of cells can be identified in the brain area by TH antibodies or by in situ hybridizations.…”

“…The distribution of catecholamines in the central nervous system (CNS) has been carefully studied (Groves et al, 1995;Hynes et al, 1995;Puelles and Verney, 1998;Ma, 1994aMa, ,b, 1997Ma, , 2003. In mammals, catecholamines are primarily found in the forebrain and midbrain (Smeets and Reiner, 1994).…”

Dopamine D2Receptor Activity Modulates Akt Signaling and Alters GABAergic Neuron Development and Motor Behavior in Zebrafish Larvae

“…However, the interaction between the different circuits involved in these behaviors is complex. Here, we treated 3 dpf zebrafish for 2 d with a concentration of MPTP (1 M) that is lower than what is reported in most previous studies and observed a decrease in TH expression, primarily confined to pretectal DA neurons, which are known to project to the telencephalon, thalamus, and optic tectum (Ma, 2003). Our main findings are summarized in Figure 10D.…”

Evolution and expression of D2 and D3 dopamine receptor genes in zebrafish

“…Several reports have now described the organization and function of the dopamine system in zebrafish. Clusters of dopaminergic neurons have been identified in the developing embryo (Guo et al, 1999;Holzschuh et al, 2001;Rink and Wullimann, 2002b) and adult (Ma, 1994a(Ma, , b, 1997(Ma, , 2003. Immunocytochemical evidence suggests that zebrafish have a conserved dopaminergic projection pathway that is homologous to the human mesostriatal pathway (Rink and Wullimann, 2002a).…”