Organization of the dopaminergic innervation of forebrain areas relevant to learning: A combined immunohistochemical/retrograde tracing study in the domestic chick

Abstract

The mediorostral neostriatum/hyperstriatum ventrale (MNH) and neostriatum dorsocaudale (Ndc) of the domestic chick are crucially involved in auditory filial imprinting, whereas the lobus parolfactorius (LPO) seems to be involved in the emotional modulation of behavior. Because there is evidence that MNH and Ndc are akin to higher association areas in mammals, the present study evaluates the dopaminergic and thalamic input to these areas, as well as to the avian caudate/putamen homologue LPO, by using retrograde pathway tracing, together with dopamine (DA) and tyrosine hydroxylase (TH) immunohistochemistry. By combining DA immunohistochemistry with retrograde fluorescent tracing, we demonstrated that dopaminergic afferents to the MNH and Ndc arise mainly from the area ventralis, whereas the main dopaminergic input to the LPO arises from the substantia nigra. The main thalamic input to the MNH and LPO arises from the dorsal thalamic nuclei, n. dorsomedialis anterior and n. dorsolateralis anterior, whereas the thalamic input to the Ndc arises from the n. dorsolateralis posterior and n. subrotundus. Furthermore, there are reciprocal intratelencephalic connections between distinct parts of the neostriatum caudale and the mediorostral neostriatum. DA-immunoreactive (ir) fibers are present at moderate densities in the MNH and Ndc and at high densities in the LPO. At the ultrastructural level, DA- and TH-ir axon terminals in the MNH and Ndc form predominantly symmetric synaptic contacts with dendritic shafts, which are often situated in close vicinity to unstained terminals. These results indicate that the general organization of dopaminergic afferents to the chick telecephalon is similar to that of the mesotelencephalic dopaminergic subsystems in mammals such as the mesostriatal and mesolimbocortical DA system.

Revised nomenclature for avian telencephalon and some related brainstem nuclei

“…This is the case for the nucleus tegmenti pedunculopontinus pars compacta, located in the diencephalic-mesencephalic tegmentum . This cell field contains a large population of dopaminergic neurons that send a massive dopaminergic innervation to the striatal part of the basal ganglia in birds (i.e., the regions that have been called lobus parolfactorius and paleostriatum augmentatum; Kitt and Brauth, 1986a,b;Bailhache and Balthazart, 1993;Reiner et al, 1994;Szekely et al, 1994;Karle et al, 1996;Metzger et al, 1996; Durstewitz et al, 1999) and therefore is accepted as homologous to the substantia nigra pars compacta of other vertebrates Smeets and Reiner, 1994;Medina and Reiner, 1995;Reiner et al, 1998a). The name applied to this region in Karten and Hodos (1967) and in many subsequent atlases and published papers, however, incorrectly suggests a homology with the pedunculopontine tegmental nucleus of mammals, located in rhombomere 1.…”

Competitor suppresses neuronal representation of food reward in the nucleus accumbens/medial striatum of domestic chicks

“…Tract tracing studies have so far revealed inputs from a wide range of pallial structures (i.e., avian homologues of isocortex such as the arcopallium and nidopallium) [54], the subpallial thalamus [55], and neuromodulatory nuclei including the ventral tegmental area (VTA) and substantia nigra (SN) for dopaminergic afferents [56][57][58][59], and the raphe nuclei in the pons for serotonergic afferents [60].…”

The Endomorphin System and Its Evolving Neurophysiological Role

“…These data demonstrated that endomorphin-1 impaired long-term memory through 1 -opioid and endomorphin-2 through 2 -opioid receptors. Freeman and Young (2000) demonstrated that passive avoidance learning in chicks disrupted by endomorphin-2 may involve cytosolic and mitochondrial protein synthesis within the lobus paraolfactorius, which constitutes a structure homologous to the caudate putamen in mammals (Veenman et al, 1995;Metzger et al, 1996;Durstewitz et al, 1999). Endomorphin-2 was shown to reverse the amnesic effects of anisomycin and blocked cytosolic protein inhibition in this structure.…”