Aggressive but not reproductive boldness in male green anole lizards correlates with baseline vasopressin activity.

Across species, individuals within a population differ in their level of boldness in social encounters with conspecifics. This boldness phenotype is often stable across both time and social context (e.g.

Social boldness correlates with brain gene expression in male green anoles.

Within populations, some individuals tend to exhibit a bold or shy social behavior phenotype relative to the mean. The neural underpinnings of these differing phenotypes - also described as syndromes, personalities, and coping styles - is an area of ongoing investigation. Although a social decision-making network has been described across vertebrate taxa, most studies examining activity within this network do so in relation to exhibited differences in behavioral expression.

Small mammal glucocorticoid concentrations vary with forest fragment size, trap type, and mammal taxa in the Interior Atlantic Forest.

Species that live in degraded habitats often show signs of physiological stress. Glucocorticoid hormones (e.g.

Serotonergic activation during courtship and aggression in the brown anole, .

The role of serotonin (5-hydroxytryptamine, 5-HT) in social behavior regulation is not fully understood. While 5-HT release in nuclei of the social behavior network has generally been associated with inhibition of aggressive behavior across multiple classes of vertebrates, less is known about its effects on sexual, especially non-copulatory courtship display behaviors. Furthermore, most research has examined effects at 5-HT release sites, while studies examining the behavioral relevance of source cell populations have generated contradictory findings.

Involvement of different mesotocin (oxytocin homologue) populations in sexual and aggressive behaviours of the brown anole.

The oxytocin (OT) family of neuropeptides are known to modulate social behaviours and anxiety in mammals and birds. We investigated cell numbers and neural activity, assessed as Fos induction, within magnocellular and parvocellular populations of neurons producing the OT homologue mesotocin (MT, Ile(8)-oxytocin). This was conducted within the male brown anole lizard, Anolis sagrei, following agonistic or courtship encounters with a conspecific.

Neural activity in catecholaminergic populations following sexual and aggressive interactions in the brown anole, Anolis sagrei.

Social behaviors in vertebrates are modulated by catecholamine (CA; dopamine, norepinephrine, epinephrine) release within the social behavior neural network. Few studies have examined activity across CA populations in relation to social behaviors. The involvement of CAs in social behavior regulation is especially underexplored in reptiles, relative to other amniotes.

Effect of stress on female-specific ornamentation.

Signal honesty is theorized to be maintained by condition-dependent trait expression. However, the mechanisms mediating the condition dependence of sexually selected traits are often unknown. New work suggests that elevated glucocorticoid levels during physiological stress may play a role in maintaining signal honesty.

Aggression- and sex-induced neural activity across vasotocin populations in the brown anole.

Activity within the social behavior neural network is modulated by the neuropeptide arginine vasotocin (AVT) and its mammalian homologue arginine vasopressin (AVP). However, central AVT/AVP release causes different behavioral effects across species and social environments. These differences may be due to the activation of different neuronal AVT/AVP populations or to similar activity patterns causing different behavioral outputs.

Estrogenic regulation of dopaminergic neurons in the opportunistically breeding zebra finch.

Steroid-induced changes in dopaminergic activity underlie many correlations between gonadal hormones and social behaviors. However, the effects of steroid hormones on the various behaviorally relevant dopamine cell groups remain unclear, and ecologically relevant species differences remain virtually unexplored. We examined the effects of estradiol (E2) manipulations on dopamine (DA) neurons of male and female zebra finches (Taeniopygia guttata), focusing on numbers of tyrosine hydroxylase-immunoreactive (TH-ir) cells in the A8-A15 cell groups, and on TH colocalization with Fos, conducted in the early A.

Vasotocin neurons and septal V1a-like receptors potently modulate songbird flocking and responses to novelty.

Previous comparisons of territorial and gregarious finches (family Estrildidae) suggest the hypothesis that arginine vasotocin (VT) neurons in the medial bed nucleus of the stria terminalis (BSTm) and V(1a)-like receptors in the lateral septum (LS) promote flocking behavior. Consistent with this hypothesis, we now show that intraseptal infusions of a V(1a) antagonist in male zebra finches (Taeniopygia guttata) reduce gregariousness (preference for a group of 10 versus 2 conspecific males), but have no effect on the amount of time that subjects spend in close proximity to other birds ("contact time"). The antagonist also produces a profound increase in anxiety-like behavior, as exhibited by an increased latency to feed in a novelty-suppressed feeding test.

Cryptic regulation of vasotocin neuronal activity but not anatomy by sex steroids and social stimuli in opportunistic desert finches.

In most vertebrate species, the production of vasotocin (VT; non-mammals) and vasopressin (VP; mammals) in the medial bed nucleus of the stria terminalis (BSTm) waxes and wanes with seasonal reproductive state; however, opportunistically breeding species might need to maintain high levels of this behaviorally relevant neuropeptide year-round in anticipation of unpredictable breeding opportunities. We here provide support for this hypothesis and demonstrate that these neurons are instead regulated 'cryptically' via hormonal regulation of their activity levels, which may be rapidly modified to adjust VT signaling. First, we show that combined treatment of male and female zebra finches (Estrildidae: Taeniopygia guttata) with the androgen receptor antagonist flutamide and the aromatase inhibitor 1,4,6-androstatriene-3,17-dione does not alter the expression of VT immunoreactivity within the BSTm; however, both hormonal treatment and social housing environment (same-sex versus mixed-sex) alter VT colocalization with the immediate early gene product Fos (a proxy marker of neural activation) in the BSTm.

Mesotocin and nonapeptide receptors promote estrildid flocking behavior.

Proximate neural mechanisms that influence preferences for groups of a given size are almost wholly unknown. In the highly gregarious zebra finch (Estrildidae: Taeniopygia guttata), blockade of nonapeptide receptors by an oxytocin (OT) antagonist significantly reduced time spent with large groups and familiar social partners independent of time spent in social contact. Opposing effects were produced by central infusions of mesotocin (MT, avian homolog of OT).

Dopaminergic regulation of mate competition aggression and aromatase-Fos colocalization in vasotocin neurons.

Recent experiments demonstrate that aggressive competition for potential mates involves different neural mechanisms than does territorial, resident-intruder aggression. However, despite the obvious importance of mate competition aggression, we know little about its regulation. Immediate early gene experiments show that in contrast to territorial aggression, mate competition in finches is accompanied by the activation of neural populations associated with affiliation and motivation, including vasotocin (VT) neurons in the medial bed nucleus of the stria terminalis (BSTm) and midbrain dopamine (DA) neurons that project to the BSTm.

Dynamic limbic networks and social diversity in vertebrates: from neural context to neuromodulatory patterning.

Vertebrate animals exhibit a spectacular diversity of social behaviors, yet a variety of basic social behavior processes are essential to all species. These include social signaling; discrimination of conspecifics and sexual partners; appetitive and consummatory sexual behaviors; aggression and dominance behaviors; and parental behaviors (the latter with rare exceptions). These behaviors are of fundamental importance and are regulated by an evolutionarily conserved, core social behavior network (SBN) of the limbic forebrain and midbrain.

Dynamic neuromodulation of aggression by vasotocin: influence of social context and social phenotype in territorial songbirds.

The homologous neuropeptides vasotocin (VT) and vasopressin (VP) influence agonistic behaviours across many taxa, but peptide-behaviour relationships are complex and purportedly species-specific. Putative species-specific effects in songbirds are confounded with context, however, such that territorial species have been tested only in resident-intruder paradigms and gregarious species have been tested only in a mate competition paradigm. Using the territorial violet-eared waxbill (Estrildidae: Uraeginthus granatina), we now show that a V(1a) receptor antagonist reduces male aggression during mate competition (as in gregarious finches), but does not affect resident-intruder aggression in dominant males.

Midbrain dopamine neurons reflect affiliation phenotypes in finches and are tightly coupled to courtship.

Mesolimbic dopamine (DA) circuits mediate a wide range of goal-oriented behavioral processes, and DA strongly influences appetitive and consummatory aspects of male sexual behavior. In both birds and mammals, mesolimbic projections arise primarily from the ventral tegmental area (VTA), with a smaller contribution from the midbrain central gray (CG). Despite the well known importance of the VTA cell group for incentive motivation functions, relationships of VTA subpopulations to specific aspects of social phenotype remain wholly undescribed.

Endogenous vasotocin exerts context-dependent behavioral effects in a semi-naturalistic colony environment.

Arginine vasotocin (VT), and its mammalian homologue arginine vasopressin (VP), are neuropeptides involved in the regulation of social behaviors and stress responsiveness. Previous research has demonstrated opposing effects of VT/VP on aggression in different species. However, these divergent effects were obtained in different social contexts, leading to the hypothesis that different populations of VT/VP neurons regulate behaviors in a context-dependent manner.

Arginine vasotocin (AVT) immunoreactivity relates to testosterone but not territorial aggression in the tree lizard, Urosaurus ornatus.

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.

Aggression frequency and intensity, independent of testosterone levels, relate to neural activation within the dorsolateral subdivision of the ventromedial hypothalamus in the tree lizard Urosaurus ornatus.

The mechanisms by which testosterone regulates aggression are unclear and may involve changes that alter the activity levels of one or more brain nuclei. We estimate neural activity by counting immunopositive cells against phosphorylated cyclic AMP response element binding protein (pCREB). We demonstrate increased pCREB immunoreactivity within the dorsolateral subdivision of the ventromedial hypothalamus (VMHdl) following an aggressive encounter in male tree lizards Urosaurus ornatus.

Steroid hormones alter neuroanatomy and aggression independently in the tree lizard.

Steroid hormones effect changes in both neuroanatomy and aggressive behavior in animals of various taxa. However, whether changes in neuroanatomy directly underlie changes in aggression is unknown. We investigate this relationship among steroid hormones, neuroanatomy, and aggression in a free-living vertebrate with a relatively simple nervous system, the tree lizard (Urosaurus ornatus).

Steroid hormone mediation of limbic brain plasticity and aggression in free-living tree lizards, Urosaurus ornatus.

The neural mechanisms by which steroid hormones regulate aggression are unclear. Although testosterone and its metabolites are involved in both the regulation of aggression and the maintenance of neural morphology, it is unknown whether these changes are functionally related. We addressed the hypothesis that parallel changes in steroid levels and brain volumes are involved in the regulation of adult aggression.