Arginine Vasotocin (AVT) Immunoreactivity Relates to Testosterone but Not Territorial Aggression in the Tree Lizard, <i>Urosaurus ornatus</i>

Abstract

The neuropeptide arginine vasotocin (AVT) and its mammalian homologue arginine vasopressin (AVP) are neuromodulators known to be steroid sensitive and associated with social behaviors in a number of vertebrate taxa. However, the role of AVT/P in the regulation of aggression remains unclear and contrasting effects of this peptide on aggression are seen in differing species and contexts. In this study, we used immunohistochemistry to examine the effects of testosterone on the AVT system in male and female tree lizards, Urosaurus ornatus, and to determine whether AVT is related to territorial aggression in this species. Tree lizards are a free-living species that exhibit natural hormonal fluctuations across breeding seasons. We detected a male-biased sexual dimorphism in centrally projecting AVT fibers within the limbic system. Furthermore, changes with season, reproductive state, and hormonal treatment suggest that testosterone regulates AVT immunoreactivity in limbic brain regions, especially in the bed nucleus of the stria terminalis. Testosterone also affects AVT immunoreactivity in peripherally projecting cell clusters, as well as the size of AVT cell bodies in the paraventricular nucleus. Although higher testosterone levels alter AVT immunoreactivity, and are known to increase the frequency and intensity of male-male aggression in this species, no individual correlations between AVT immunoreactivity and aggression were detected.

Unpredictable food availability induces metabolic and hormonal changes independent of food intake in a sedentary songbird

“…The most common interpretation of immunohistochemistry data is that immunostaining indicates a matching of peptide release with production (Panzica et al, 2001;Kabelik et al, 2008;Sewall et al, 2010) and thus greater ME staining would reflect a larger release of AVT into the hypophyseal portal system (Fokidis and Deviche, 2012). Based on this interpretation, the data are consistent with the higher initial CORT levels observed in the variable compared with the constant feeding group, and thus feeding treatment influenced the amount of AVT released during acute handling stress.…”

“…Thrashers subjected to variable food availability had higher ME staining intensity than birds with access to consistent amounts of food, and this observation is opposite to our predicted response, based on the wild bird research. However, replicating ecological conditions in captivity is inherently difficult, and the randomized availability of food in this study imperfectly mimics the seasonal variation in food resources in the desert, which are less stochastic in nature.The most common interpretation of immunohistochemistry data is that immunostaining indicates a matching of peptide release with production (Panzica et al, 2001;Kabelik et al, 2008;Sewall et al, 2010) and thus greater ME staining would reflect a larger release of AVT into the hypophyseal portal system (Fokidis and Deviche, 2012). Based on this interpretation, the data are consistent with the higher initial CORT levels observed in the variable compared with the constant feeding group, and thus feeding treatment influenced the amount of AVT released during acute handling stress.…”

Arginine vasotocin, steroid hormones, and social behavior in the green anole lizard, Anolis carolinensis

“…In addition, there is evidence for interactions between AVT/AVP and steroid hormones, providing a potential mechanism through which behavioral variability and contextdependent responses could be achieved. For example, AVT/AVP cells are androgen sensitive and castration reduces immunoreactive cell number [in rodents (Miller et al, 1992;Wang and De Vries, 1993;Boyd, 1997;Kabelik et al, 2008) and reptiles (Kabelik et al, 2008)]. …”

Cryptic Regulation of Vasotocin Neuronal Activity but Not Anatomy by Sex Steroids and Social Stimuli in Opportunistic Desert Finches

“…forebrain, particularly the lateral septum (LS) Voorhuis et al, 1988;Crenshaw et al, 1992;Viglietti-Panzica et al, 1992;Wang and De Vries, 1993;reviews: De Vries and Panzica, 2006;Goodson, 2008;Boyd, 1994;Dubois-Dauphin et al, 1994;Lakhdar-Ghazal et al, 1995;Plumari et al, 2004;Kabelik et al, 2008]. Levels of VT and its mammalian homologue VP are highly dependent on circulating steroid hormone levels and thus often vary with hormonal changes across breeding season and photoperiod [e.g., Moore et al, 2000;Kabelik et al, 2008;Rasri et al, 2008;reviews: De Vries and Boyle, 1998;Goodson and Bass, 2001].…”

“…Levels of VT and its mammalian homologue VP are highly dependent on circulating steroid hormone levels and thus often vary with hormonal changes across breeding season and photoperiod [e.g., Moore et al, 2000;Kabelik et al, 2008;Rasri et al, 2008;reviews: De Vries and Boyle, 1998;Goodson and Bass, 2001]. These seasonal changes might be relevant for numerous behaviors that are influenced by VT/VP, such as communication, pair bonding, aggression, social recognition, non-sexual affiliation, and parental behaviors [Goodson and Bass, 2001;Marler et al, 2003;De Vries and Panzica, 2006;Lim and Young, 2006;Caldwell et al, 2008;Veenema and Neumann, 2008].…”