Article

Neural distribution of nonapeptide binding sites in two species of songbird.

Department of Psychology, Emory University, Atlanta, Georgia 30322, USA.
The Journal of Comparative Neurology (impact factor: 3.81). 02/2009; 513(2):197-208. DOI:10.1002/cne.21947
Source: PubMed

ABSTRACT Vasotocin (VT) and its mammalian homologue, vasopressin (VP), modulate many social behaviors in a variety of vertebrate species. In songbirds, the effects of centrally administered VT vary according to species, which may reflect species-specific distributions of VT binding sites. Different radioligands used to map receptors in previous autoradiographical studies have revealed nonoverlapping distributions of VT binding, suggesting a heterogeneous population of more than one type of VT receptor. For two model songbird species, the white-throated sparrow (Zonotrichia albicollis) and zebra finch (Taeniopygia guttata), we labeled putative VT receptors with two radioligands, [(125)I]ornithine vasotocin analog ([(125)I]OVTA) and [(125)I]linear VP antagonist ([(125)I]HO-LVA). Competitive binding assays in the lateral septum showed that both ligands were effectively displaced by both VT and a related nonapeptide, mesotocin (MT), showing that these radioligands, which were developed to label mammalian nonapeptide receptors, label at least one population of related receptors in songbirds. [(125)I]OVTA labeled receptors throughout the telencephalon, diencephalon, midbrain, and brainstem, with a similar distribution in both species. In contrast, the binding of [(125)I]HO-LVA was restricted to the septal area, dorsal arcopallium, and optic tectum in sparrow and was essentially undetectable in zebra finch. Because the avian brain is likely to express multiple types of VT receptors, we hypothesize that the binding patterns of these radioligands represent a heterogeneous receptor population.

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Keywords

binding patterns
 
Competitive binding assays
 
Different radioligands
 
heterogeneous population
 
heterogeneous receptor population
 
label mammalian nonapeptide receptors
 
mammalian homologue
 
map receptors
 
model songbird species
 
previous autoradiographical studies
 
putative VT receptors
 
septal area
 
social behaviors
 
vertebrate species
 
VT binding
 
VT binding sites
 
VT receptor
 
VT receptors
 
white-throated sparrow
 
Zonotrichia albicollis
 

Cary H Leung