Neurochemical compartmentalization within the pigeon basal ganglia

Abstract

The goals of this study were to use multiple informative markers to define and characterize the neurochemically distinct compartments of the pigeon basal ganglia, especially striatum and accumbens. To this end, we used antibodies against 12 different neuropeptides, calcium-binding proteins or neurotransmitter-related enzymes that are enriched in the basal ganglia. Our results clarify boundaries between previously described basal ganglia subdivisions in birds, and reveal considerable novel heterogeneity within these previously described subdivisions. Sixteen regions were identified that each displayed a unique neurochemical organization. Four compartments were identified within the dorsal striatal region. The neurochemical characteristics support previous comparisons to part of the central extended amygdala, somatomotor striatum, and associational striatum of mammals, respectively. The medialmost part of the medial striatum, however, has several unique features, including prominent pallidal-like woolly fibers and thus may be a region unique to birds. Four neurochemically distinct regions were identified within the pigeon ventral striatum: the accumbens, paratubercular striatum, ventrocaudal striatum, and the ventral area of the lateral part of the medial striatum that is located adjacent to these regions. The pigeon accumbens is neurochemically similar to the mammalian rostral accumbens. The pigeon paratubercular and ventrocaudal striatal regions are similar to the mammalian accumbens shell. The ventral portions of the medial and lateral parts of the medial striatum, which are located adjacent to accumbens shell-like areas, have neurochemical characteristics as well as previously reported limbic connections that are comparable to the accumbens core. Comparisons to neurochemically identified compartments in reptiles, mammals, and amphibians indicate that, although most of the basic compartments of the basal ganglia were highly conserved during tetrapod evolution, uniquely avian compartments may exist as well.

Transmitter receptors reveal segregation of the arcopallium/amygdala complex in pigeons (Columba livia)

“…Both, CeA and MeA are the major output nuclei of the amygdala and confluent with the BST nuclei (Swanson, ). Comparative studies in chick and mouse embryo with subpallial and pallial genetic markers, as well as connectivity data suggests that the BST nuclei BSTM and BSTL in birds belong to the extended amygdala nuclei (Abellán & Medina, ; Abellán, Menuet, Dehay, Medina, & Retaux, ; Bruce, Erichsen, & Reiner, ; Butler et al, ; Medina et al, ; Puelles et al, ; Puelles et al, ). In birds, it has been further postulated that SpA and BSTL form the central extended amygdala complex, while TnA and BSTM form another functional unit and may correspond to the medial extended amygdala complex (Puelles et al, ; Reiner et al, ; Abellán & Medina, ; Kuenzel et al, ).…”

Regional Patterning of Adult Neurogenesis in the Homing Pigeon’s Brain

“…CB and CR were used as markers that indicate late integrative phases of adult neurons. Besides, they are common markers for neurons that are typically bound to established neuronal networks in birds and mammals ( Baimbridge et al, 1992 ; Hof et al, 1999 ; Heyers et al, 2008 ; Bruce et al, 2016 ). Ki67, a nuclear protein, is a proliferative marker and was expressed in dividing cells for the entire duration of their mitotic process ( Kee et al, 2002 ).…”

Telencephalic regulation of the HPA axis in birds

“…Interestingly, the subregions of the NTS that receive projections from the BSTL are the same subregions that also receive projections from the PVN ( Berk, 1987 ; Berk and Finkelstein, 1983 ), reinforcing the idea that these areas form part of the same circuit. BSTL contains mainly GABA-ergic projection neurons ( Bruce et al, 2016 ; Real et al, 2008 ), as in mammals, but also CRH + neurons ( Ball et al, 1989 ; Józsa et al, 1984 ; Richard et al, 2004 ). BSTL (at least at the level of the anterior commissure) is activated by the acute stress of a brief restraint in song sparrows ( Melospiza melodia ) ( Goodson and Evans, 2004 ) and chickens ( Nagarajan et al, 2014 ).…”