Autoradiographic Characterization of Binding Sites Labelled with Vasopressin in the Brain of a Urodele Amphibian

Abstract

Because arginine vasotocin (AVT) activates male sexual behaviors in the rough-skinned newt (Taricha granulosa), quantitative autoradiography with radiolabelled arginine vasopressin (³H-AVP) was used to characterize putative AVT receptors in the telencephalon of this amphibian. Analyses were restricted to specific binding sites in the medial pallium, although dense binding also was observed in the dorsal pallium and amygdala pars lateralis. Binding of ³H-AVP to these sites was saturable, specific, reversible, of high affinity (Kd= 1 nM) and low capacity (57 fmol/mg protein). The rank order of potency of related peptides in inhibiting ³H-AVP binding was as follows: AVT > d(CH2)5[Tyr(Me)²]AVP (a mammalian pressor antagonist) > AVP, oxytocin, and [dPen¹Tyr(Me)²]AVP (also a pressor antagonist) > mesotocin ≫ desGly(NH2)AVP, AVP fragment 4–9 and pressinoic acid. Thus, these binding sites appear to represent authentic central nervous system receptors for AVT. Furthermore, ligand specificity for the binding sites in this amphibian differ from that reported for AVP binding sites in rat brains. The AVT receptors in the medial pallium, dorsal pallium, and amygdala pars lateralis may represent site(s) of action where AVT elicits sexual behaviors in male T. granulosa.

Neuroanatomical distribution of vasotocin in a urodele amphibian (Taricha granulosa) revealed by immunohistochemical and in situ hybridization techniques

“…We observed a fine, granular, VTir staining within the entire rostrocaudal extent of the medial pallium of T. granulosa, similar to that observed previously in the urodele amphibian P. waltlii (Gonzá lez and Smeets, 1992a). These observations are consistent with the relatively high concentration of VT-measured with radioimmunoassay techniques in microdissected tissues (Zoeller and Moore, 1986a)-and high density of VT binding sites in the medial pallium of T. granulosa (Tripp and Moore, 1988;Boyd and Moore, 1991). Vasopressinergic fibers may be a common feature of the mammalian hippocampal complex (Dubois-Dauphin and Zakarian, 1987;Caffé et al, 1989).…”

Localization of three types of arginine vasotocin receptors in the brain and pituitary of the newt Cynops pyrrhogaster

“…Binding sites of tritiated AVP in the brain of the roughskinned newt T. granulosa have been described by Tripp and Moore (1988) and by Boyd and Moore (1991). According to these authors, the specific binding sites are the olfactory bulb, medial pallium, dorsal pallium, amygdala, and tegmental region of the medulla oblongata.…”

Species, sex and individual differences in the vasotocin/vasopressin system: Relationship to neurochemical signaling in the social behavior neural network

“…The distribution of AVT receptors has been studied in fish(Moons and others, 1989; Kline and others, 2011; Lema and others, 2012; Huffman and others, 2012) and amphibians(Tripp and Moore, 1988; Boyd and Moore, 1991; Acharjee and others, 2004; Lewis and others, 2005; Hasunuma and others, 2010; Hasunuma and others, 2013) and birds (Voorhuis and others, 1988; Voorhuis and others, 1990; Goodson and others, 2006; Leung and others, 2009; Leung and others, 2011), but not yet in reptiles. The vast majority of data on the distribution of nonapeptide receptors, however, comes from mammals.…”