Ovarian hormones alter the behavioral response of the medial preoptic anterior hypothalamus to arginine-vasopressin

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

Arginine-vasotocin (AVT)/arginine vasopressin (AVP) are members of the AVP/oxytocin (OT) superfamily of peptides that are involved in the regulation of social behavior, social cognition and emotion. Comparative studies have revealed that AVT/AVP and their receptors are found throughout the "social behavior neural network (SBNN)" and display the properties expected from a signaling system that controls social behavior (i.e., species, sex and individual differences and modulation by gonadal hormones and social factors). Neurochemical signaling within the SBNN likely involves a complex combination of synaptic mechanisms that co-release multiple chemical signals (e.g., classical neurotransmitters and AVT/AVP as well as other peptides) and non-synaptic mechanisms (i.e., volume transmission). Crosstalk between AVP/OT peptides and receptors within the SBNN is likely. A better understanding of the functional properties of neurochemical signaling in the SBNN will allow for a more refined examination of the relationships between this peptide system and species, sex and individual differences in sociality.

The medial preoptic area is necessary for sexual odor preference, but not sexual solicitation, in female Syrian hamsters

Precopulatory behaviors that are preferentially directed towards opposite-sex conspecifics are critical for successful reproduction, particularly in species wherein the sexes live in isolation, such as Syrian hamsters (Mesocricetus auratus). In females, these behaviors include sexual odor preference and vaginal scent marking. The neural regulation of precopulatory behaviors is thought to involve a network of forebrain areas that includes the medial amygdala (MA), the bed nucleus of the stria terminalis (BNST), and the medial preoptic area (MPOA). Although MA and BNST are necessary for sexual odor preference and preferential vaginal marking to male odors, respectively, the role of MPOA in odor-guided female precopulatory behaviors is not well understood. To address this issue, female Syrian hamsters with bilateral, excitotoxic lesions of MPOA (MPOA-X) or sham lesions (SHAM) were tested for sexual odor investigation, scent marking, and lordosis. MPOA-X females did not investigate male odors more than female odors in an odor preference test, indicating that MPOA may be necessary for normal sexual odor preference in female hamsters. This loss of preference cannot be attributed to a sensory deficit, since MPOA-X females successfully discriminated male odors from female odors during an odor discrimination test. Surprisingly, no deficits in vaginal scent marking were observed in MPOA-X females, although these females did exhibit decreased overall levels of flank marking compared to SHAM females. Finally, all MPOA-X females exhibited lordosis appropriately. These results suggest that MPOA plays a critical role in the neural regulation of certain aspects of odor-guided precopulatory behaviors in female Syrian hamsters.

The regulation of social recognition, social communication and aggression: vasopressin in the social behavior neural network

Neuropeptides in the arginine vasotocin/arginine vasopressin (AVT/AVP) family play a major role in the regulation of social behavior by their actions in the brain. In mammals, AVP is found within a circuit of recriprocally connected limbic structures that form the social behavior neural network. This review examines the role played by AVP within this network in controlling social processes that are critical for the formation and maintenance of social relationships: social recognition, social communication and aggression. Studies in a number of mammalian species indicate that AVP and AVP V1a receptors are ideally suited to regulate the expression of social processes because of their plasticity in response to factors that influence social behavior. The pattern of AVP innervation and V1a receptors across the social behavior neural network may determine the potential range and intensity of social responses that individuals display in different social situations. Although fundamental information on how social behavior is wired in the brain is still lacking, it is clear that different social behaviors can be influenced by the actions of AVP in the same region of the network and that AVP can act within multiple regions of this network to regulate the expression of individual social behaviors. The existing data suggest that AVP can influence social behavior by modulating the interpretation of sensory information, by influencing decision making and by triggering complex motor outputs. This article is part of a Special Issue entitled Oxytocin, Vasopressin, and Social Behavior.

Photoperiodic regulation of vasopressin receptor binding in female Syrian hamsters

During long "summer-like" photoperiods, female Syrian hamsters display a regular 4-day estrous cycle. However, during short "winter-like" photoperiods (<12.5 h of light/day) hamsters become anestrus. Short photoperiod exposure eliminates reproductive behavior but social behaviors such as aggression and scent marking continue to be displayed. In long photoperiods, the types and intensity of social behaviors change as a function of the estrous cycle. For example, aggression and scent marking tend to occur at higher levels on diestrus 1 and diestrus 2 than on proestrus or estrus. Aggression and scent marking may be regulated, at least in part, by changes in the density of arginine vasopressin-V(1a) receptors (V(1a)R). In Experiment 1, it was hypothesized that the density of V(1a)R would change across the estrous cycle in several subcortical regions implicated in the regulation of aggression and scent marking. In Experiment 2, it was hypothesized that exposure to short photoperiod would alter the density of V(1a)R in several regions involved in the regulation of social behavior. Interestingly, there were no dramatic changes in V(1a)R binding across the estrous cycle within any of the neuroanatomical areas measured. However, in hamsters housed in short photoperiod, there were lower levels of V(1a)R binding within the medial preoptic nucleus (MPN), medial preoptic area (MPO), lateral hypothalamus (LH), central nucleus of the amygdala (Ce) and bed nucleus of the stria terminalis (BST) than in hamsters housed in long photoperiod. These data suggest that photoperiodic mechanisms can alter the density of V(1a)R in subset of V(1a) binding sites thought to be involved in the regulation of social behaviors in female hamsters.

Oxytocin inhibits aggression in female Syrian hamsters

Dominant subordinate relationships are formed as the result of social conflict and are maintained at least in part by communication. At this time, little is known about the neural mechanisms that are responsible for coordinating the social behaviours (e.g. aggression) that occur in association with the formation and maintenance of these relationships. The purpose of the present study was to investigate the role of oxytocin (OXT) within the medial preoptic anterior hypothalamic continuum (MPOA-AH) in the control of aggression in female hamsters. OXT injected into the MPOA-AH immediately before testing significantly reduced the duration of aggression in a dose-dependent manner. Injection of an OXT antagonist 30 min before testing significantly increased the duration of aggression. In contrast, the duration of aggression was not altered when hamsters were tested either 30 min after injection of OXT or immediately following injection of an OXT-antagonist. These data support the hypothesis that OXT release within the MPOA-AH regulates social behaviours important in the formation and maintenance of dominant subordinate relationships in female hamsters.

Effects of peptides on animal and human behavior: a review of studies published in the first twenty years of the journal Peptides

This review catalogs effects of peptides on various aspects of animal and human behavior as published in the journal Peptides in its first twenty years. Topics covered include: activity levels, addiction behavior, ingestive behaviors, learning and memory-based behaviors, nociceptive behaviors, social and sexual behavior, and stereotyped and other behaviors. There are separate tables for these behaviors and a short introduction for each section.

Social behavior functions and related anatomical characteristics of vasotocin/vasopressin systems in vertebrates

The neuropeptide arginine vasotocin (AVT; non-mammals) and its mammalian homologue, arginine vasopressin (AVP) influence a variety of sex-typical and species-specific behaviors, and provide an integrational neural substrate for the dynamic modulation of those behaviors by endocrine and sensory stimuli. Although AVT/AVP behavioral functions and related anatomical features are increasingly well-known for individual species, ubiquitous species-specificity presents ever increasing challenges for identifying consistent structure-function patterns that are broadly meaningful. Towards this end, we provide a comprehensive review of the available literature on social behavior functions of AVT/AVP and related anatomical characteristics, inclusive of seasonal plasticity, sexual dimorphism, and steroid sensitivity. Based on this foundation, we then advance three major questions which are fundamental to a broad conceptualization of AVT/AVP social behavior functions: (1) Are there sufficient data to suggest that certain peptide functions or anatomical characteristics (neuron, fiber, and receptor distributions) are conserved across the vertebrate classes? (2) Are independently-evolved but similar behavior patterns (e.g. similar social structures) supported by convergent modifications of neuropeptide mechanisms, and if so, what mechanisms? (3) How does AVT/AVP influence behavior - by modulation of sensorimotor processes, motivational processes, or both? Hypotheses based upon these questions, rather than those based on individual organisms, should generate comparative data that will foster cross-class comparisons which are at present underrepresented in the available literature.

Vasopressin (V1a) receptor binding, mRNA expression and transcriptional regulation by androgen in the Syrian hamster brain

Arginine vasopressin plays an important role in the regulation of social behaviours in rodents. In the Syrian hamster, vasopressin injected directly into the brain stimulates scent marking and aggressive behaviour in a steroid dependent manner and is therefore a useful model for investigating steroid-peptide-behaviour interactions. In this study, we used in situ hybridization and radioligand binding assays on adjacent sections of hamster brains to compare the relative distribution of vasopressin (V1a) receptor mRNA and V1a receptor binding. V1a receptor mRNA and binding are abundant in the lateral septum, bed nucleus of the stria terminalis, medial preoptic nucleus, anterodorsal thalamus and suprachiasmatic nucleus. Moderate receptor binding and low levels of receptor mRNA are present in the central nucleus of the amygdala and a lateral zone from the medial preoptic area through the anterior hypothalamus. V1a receptor mRNA is anatomically more restricted in several areas compared to the ligand binding pattern, which is consistent with significant spread of receptor protein along neuronal processes. Comparison of V1a receptor ligand binding and mRNA in intact, castrated, and castrated-testosterone treated animals reveals that V1a receptors in the medial preoptic nucleus are regulated by androgen, most likely by an upregulation of V1a receptor gene expression in a cluster of neurones concentrated in the ventromedial part of this nucleus. This study confirms the presence of the V1a subtype of vasopressin receptors in behaviourally important regions of the hamster brain and suggests that transcriptional regulation by gonadal steroids may play a role in modulating behavioural sensitivity to vasopressin.

Effects of gonadotropin-releasing hormones, corticotropin-releasing hormone, and vasopressin on female sexual behavior

The effects of intracerebroventricular (icv) infusion of four neuropeptides on female sexual behavior were examined in the female musk shrew (Suncus murinus). In the first experiment, (icv) infusion of 100 ng of the mammalian form of gonadotropin-releasing hormone (mGnRH) facilitated rapid display of receptivity. Gonadotropin-releasing hormone-infused females had shorter latencies to rump present and tail wag, compared with controls. In a second experiment, icv administration of the other form of GnRH present in musk shrew brain, the chicken GnRH-II form, produced no changes in female behavior relative to the control condition. In Experiment 3, icv delivery of corticotropin-releasing hormone (CRH) facilitated female sexual behavior, relative to vasopressin and controls. The females treated with CRH had shorter latencies to display rump present, tail wag, and for the receipt of the first missed intromission compared with females in the other treatment groups. Vasopressin increased female scent marking relative to that of CRH-treated females. These data indicate that neurohormones of the hypothalamic-pituitary-gonadal and the hypothalamic-pituitary-adrenal axes can facilitate reproductive behavior in S. murinus.

Role of vasopressin and oxytocin in the control of social behavior in Syrian hamsters (Mesocricetus auratus)

Vasopressin (VP) and oxytocin (OT) play an important role in regulating social behavior in a variety of species as a result of their actions in the central nervous system. The following paper reviews the actions of VP and OT in controlling a range of social behaviors involved in communication, aggression and reproduction in the Syrian hamster. These data suggest that social and hormonal stimuli alter the expression of specific social behaviors by altering the release of, or the response to, VP and OT within key elements of the neural circuits controlling these behaviors.

Effects of peptides: a cross-listing of peptides and their central actions published in the journal Peptides from 1994 through 1998

Effects of peptides on the central nervous system are presented in two ways so as to provide a cross-listing. In the first table, the peptides are listed alphabetically. In the second table, the central nervous system effects are arranged alphabetically. No longer can there be any doubt that peptides affect the central nervous system, sometimes in several ways.

Injection of oxytocin into the medial preoptic-anterior hypothalamus increases ultrasound production by female hamsters

Recent studies of hamsters have documented the facilitation of lordosis and other sociosexual responses by injections of oxytocin (OXT) into the medial preoptic area-anterior hypothalamus (MPOA-AH). These data suggest the regulation of social interaction and bonds by OXT. In turn, this suggests that OXT could act in the MPOA-AH to control other behaviors involved in the initiation or maintenance of social contact, including the ultrasonic vocalizations that female hamsters use to alert and attract potential mates. To test this possibility, we compared the ultrasound rates of 11 naturally estrous hamsters before and after injections of OXT (200 ng/200 nl of saline) or saline (200 nl) into the MPOA-AH. The data revealed a clear facilitation of ultrasound rate 30 min after OXT treatment. This result suggests the modulation of ultrasound rate by endogenous OXT acting within the MPOA-AH. It extends the range of social behaviors sensitive to control by OXT and supports the possibility that OXT acts within the MPOA-AH to facilitate a variety of behaviors involved in the establishment or maintenance of the social interactions required for successful reproduction. At the same time, these data extend earlier observations linking ultrasound production to the MPOA-AH, and begin to describe the peptidergic mechanisms controlling this form of reproductive behavior.