Vasopressin: behavioral roles of an "original" neuropeptide

Analysis of transcription factor mRNAs in identified oxytocin and vasopressin magnocellular neurons isolated by laser capture microdissection

The oxytocin (Oxt) and vasopressin (Avp) magnocellular neurons (MCNs) in the hypothalamus are the only neuronal phenotypes that are present in the supraoptic nucleus (SON), and are characterized by their robust and selective expression of either the Oxt or Avp genes. In this paper, we take advantage of the differential expression of these neuropeptide genes to identify and isolate these two individual phenotypes from the rat SON by laser capture microdissection (LCM), and to analyze the differential expression of several of their transcription factor mRNAs by qRT-PCR. We identify these neuronal phenotypes by stereotaxically injecting recombinant Adeno-Associated Viral (rAAV) vectors which contain cell-type specific Oxt or Avp promoters that drive expression of EGFP selectively in either the Oxt or Avp MCNs into the SON. The fluorescent MCNs are then dissected by LCM using a novel Cap Road Map protocol described in this paper, and the purified MCNs are extracted for their RNAs. qRT-PCR of these RNAs show that some transcription factors (RORA and c-jun) are differentially expressed in the Oxt and Avp MCNs.

Nonsocial functions of hypothalamic oxytocin

Oxytocin (OXT) is a hypothalamic neuropeptide composed of nine amino acids. The functions of OXT cover a variety of social and nonsocial activity/behaviors. Therapeutic effects of OXT on aberrant social behaviors are attracting more attention, such as social memory, attachment, sexual behavior, maternal behavior, aggression, pair bonding, and trust. The nonsocial behaviors/functions of brain OXT have also received renewed attention, which covers brain development, reproduction, sex, endocrine, immune regulation, learning and memory, pain perception, energy balance, and almost all the functions of peripheral organ systems. Coordinating with brain OXT, locally produced OXT also involves the central and peripheral actions of OXT. Disorders in OXT secretion and functions can cause a series of aberrant social behaviors, such as depression, autism, and schizophrenia as well as disturbance of nonsocial behaviors/functions, such as anorexia, obesity, lactation failure, osteoporosis, diabetes, and carcinogenesis. As more and more OXT functions are identified, it is essential to provide a general view of OXT functions in order to explore the therapeutic potentials of OXT. In this review, we will focus on roles of hypothalamic OXT on central and peripheral nonsocial functions.

Expression of arginine vasotocin receptors in the developing zebrafish CNS

Vasotocin/vasopressin is a neuropeptide that regulates social and reproductive behaviors in a variety of animals including fish. Arginine vasotocin (AVT) is expressed by cells in the ventral hypothalamic and preoptic areas in the diencephalon during embryogenesis in zebrafish suggesting that vasotocin might mediate other functions within the CNS prior to the development of social and reproductive behaviors. In order to examine potential early roles for vasotocin we cloned two zebrafish vasotocin receptors homologous to AVPR1a. The receptors are expressed primarily in the CNS in similar but generally non-overlapping patterns. Both receptors are expressed in the forebrain, midbrain and hindbrain by larval stage. Of note, AVTR1a-expressing neurons in the hindbrain appear to be contacted by the axons of preoptic neurons in the forebrain that include avt+ neurons and sensory axons in the lateral longitudinal fasciculus (LLF). Furthermore, AVTR1a-expressing hindbrain neurons extend axons into the medial longitudinal fasciculus (MLF) that contains axons of many neurons thought to be involved in locomotor responses to sensory stimulation. One hypothesis consistent with this anatomy is that AVT signaling mediates or gates sensory input to motor circuits in the hindbrain and spinal cord.

Plasma oxytocin and vasopressin do not predict neuropeptide concentrations in human cerebrospinal fluid

The involvement of the neuropeptides oxytocin (OXT) and vasopressin (AVP) in human socio-emotional behaviours is attracting increasing attention. There is ample evidence for elevated plasma levels upon a wide variety of social and emotional stimuli and scenarios, ranging from romantic love via marital distress up to psychopathology, with cause versus consequence being largely unclear. The present study examined whether plasma levels of both OXT and AVP are reflective of central neuropeptide levels, as assumed to impact upon socio-emotional behaviours. Concomitant plasma and cerebrospinal fluid (CSF) samples were taken from 41 non-neurological and nonpsychiatric patients under basal conditions. Although OXT and AVP levels in the CSF exceeded those in plasma, there was no correlation between both compartments, clearly suggesting that plasma OXT and AVP do not predict central neuropeptide concentrations. Thus, the validity of plasma OXT and AVP as potential biomarkers of human behaviour needs further clarification.

MicroRNA profiling in the mouse hypothalamus reveals oxytocin-regulating microRNA

Oxytocin (Oxt), produced in the hypothalamic paraventricular and supraoptic nuclei for transport to and release from the posterior pituitary, was originally discovered through its role in lactation and parturition. Oxt also plays important roles in the central nervous system by influencing various behaviors. MicroRNAs (miRNAs), endogenous regulators of many genes, are a class of small non-coding RNAs that mediate post-transcriptional gene silencing. We performed miRNA expression profiling of the mouse hypothalamus by deep sequencing. Among the sequenced and cross-mapped small RNAs, expression of known miRNAs and unknown miRNAs candidates were analyzed. We investigated in detail one miRNA, miR-24, and found that it is a novel regulator of Oxt and controls both transcript and peptide levels of Oxt. These results provide insights into potential neurohypophysial hormone regulation mediated by miRNAs.

Psychobiological mechanisms underlying the social buffering of the hypothalamic-pituitary-adrenocortical axis: a review of animal models and human studies across development

Discovering the stress-buffering effects of social relationships has been one of the major findings in psychobiology in the last century. However, an understanding of the underlying neurobiological and psychological mechanisms of this buffering is only beginning to emerge. An important avenue of this research concerns the neurocircuitry that can regulate the activity of the hypothalamic-pituitary-adrenocortical (HPA) axis. The present review is a translational effort aimed at integrating animal models and human studies of the social regulation of the HPA axis from infancy to adulthood, specifically focusing on the process that has been named social buffering. This process has been noted across species and consists of a dampened HPA axis stress response to threat or challenge that occurs with the presence or assistance of a conspecific. We describe aspects of the relevant underlying neurobiology when enough information exists and expose major gaps in our understanding across all domains of the literatures we aimed to integrate. We provide a working conceptual model focused on the role of oxytocinergic systems and prefrontal neural networks as 2 of the putative biological mediators of this process, and propose that the role of early experiences is critical in shaping later social buffering effects. This synthesis points to both general future directions and specific experiments that need to be conducted to build a more comprehensive model of the HPA social buffering effect across the life span that incorporates multiple levels of analysis: neuroendocrine, behavioral, and social.

Arginine vasopressin-dependent and AVP-independent mechanisms of renal fluid absorption during thirsting despite glucocorticoid-mediated vasopressin suppression

OBJECTIVE

Glucocorticoids seem to modify the release and effects of plasma arginine vasopressin (pAVP). However, underlying processes are not well understood. This study aimed to evaluate the mechanism of the modulating effects of glucocorticoids on pAVP and renal water reabsorption.

DESIGN

Fluid deprivation tests were performed without (d0) and after one (d1) and five days (d5) of oral prednisolone (Pred) pretreatment in a dosage relevant to drug therapy (30 mg/day).

PATIENTS

Twelve healthy male volunteers participated in this trial.

MEASUREMENTS

Plasma and urinary osmolality, pAVP, renin, aldosterone, plasma atrial natriuretic peptide (ANP) as well as urinary secretion of aquaporin-2 (AQP2) and prostaglandin E(2) (PGE2) were analysed.

RESULTS

An appropriate rise in pAVP was observable during thirsting (P < 0.001), which was absent after Pred pretreatment. However, the plasma and urinary osmolality after Pred treatment did not differ when compared with the basal thirsting test. Unchanged urinary AQP2 excretion suggests AVP-independent mechanisms of renal fluid reabsorption. Plasma renin concentration as well as ANP was substantially increased after Pred intake at d1 and d5 (both P < 0.05), which may mediate such AVP-independent mechanisms. Urinary PGE2 secretion was not influenced by Pred pretreatment, making a PGE2-mediated effect on renal AQP2 translocation and water permeability unlikely. Increased efficacy of exogenous desmopressin at d1 and d5 indicates also a relative increase in AVP sensitivity of the tubular cells after Pred intake.

CONCLUSIONS

The here presented data are compatible with an increased AVP sensitivity and a partially AVP-independent regulation of AQP2 translocation and renal fluid reabsorption during glucocorticoid treatment.

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. We examined neural activity (assessed as Fos induction) within AVT neurons in male brown anole lizards (Anolis sagrei) participating in aggressive or sexual encounters. Lizards possess simple amniote nervous systems, and their examination provides a comparative framework to complement avian and mammalian studies. In accordance with findings in other species, AVT neurons in the anole paraventricular nucleus (PVN) were activated during aggressive encounters; but unlike in other species, a positive correlation was found between aggression levels and activation. Activation of AVT neurons within the supraoptic nucleus (SON) occurred nonspecifically with participation in either aggressive or sexual encounters. Activation of AVT neurons in the preoptic area (POA) and bed nucleus of the stria terminalis (BNST) was associated with engagement in sexual behaviors. The above findings are congruent with neural activation patterns observed in other species, even when the behavioral outputs (i.e., aggression level) differed. However, aggressive encounters also increased activation of AVT neurons in the BNST, which is incongruous with findings in other species. Thus, some species differences involve the encoding of social stimuli as different neural activation patterns within the AVT/AVP network, whereas other behavioral differences arise downstream of this system.

Genome-wide prediction of age at puberty and reproductive longevity in sows

Traditional selection for sow reproductive longevity is ineffective due to low heritability and late expression of the trait. Incorporation of DNA markers into selection programs is potentially a more practical approach for improving sow lifetime productivity. Using a resource population of crossbred gilts, we explored pleiotropic sources of variation that influence age at puberty and reproductive longevity. Of the traits recorded before breeding, only age at puberty significantly affected the probability that females would produce a first parity litter. The genetic variance explained by 1-Mb windows of the sow genome, compared across traits, uncovered regions that influence both age at puberty and lifetime number of parities. Allelic variants of SNPs located on SSC5 (27-28 Mb), SSC8 (36-37 Mb) and SSC12 (1.2-2 Mb) exhibited additive effects and were associated with both early expression of puberty and a greater than average number of lifetime parities. Combined analysis of these SNPs showed that an increase in the number of favorable alleles had positive impact on reproductive longevity, increasing number of parities by up to 1.36. The region located on SSC5 harbors non-synonymous alleles in the arginine vasopressin receptor 1A (AVPR1A) gene, a G-protein-coupled receptor associated with social and reproductive behaviors in voles and humans and a candidate for the observed effects. This region is characterized by high levels of linkage disequilibrium in different lines and could be exploited in marker-assisted selection programs across populations to increase sow reproductive longevity.

GABAergic inhibition through synergistic astrocytic neuronal interaction transiently decreases vasopressin neuronal activity during hypoosmotic challenge

The neuropeptide vasopressin is crucial to mammalian osmotic regulation. Local hypoosmotic challenge transiently decreases and then increases vasopressin secretion. To investigate mechanisms underlying this transient response, we examined the effects of hypoosmotic challenge on the electrical activity of rat hypothalamic supraoptic nucleus (SON) vasopressin neurons using patch-clamp recordings. We found that 5 min exposure of hypothalamic slices to hypoosmotic solution transiently increased inhibitory postsynaptic current (IPSC) frequency and reduced the firing rate of vasopressin neurons. Recovery occurred by 10 min of exposure, even though the osmolality remained low. The γ-aminobutyric acid (GABA)A receptor blocker, gabazine, blocked the IPSCs and the hypoosmotic suppression of firing. The gliotoxin l-aminoadipic acid blocked the increase in IPSC frequency at 5 min and the recovery of firing at 10 min, indicating astrocytic involvement in hypoosmotic modulation of vasopressin neuronal activity. Moreover, β-alanine, an osmolyte of astrocytes and GABA transporter (GAT) inhibitor, blocked the increase in IPSC frequency at 5 min of hypoosmotic challenge. Confocal microscopy of immunostained SON sections revealed that astrocytes and magnocellular neurons both showed positive staining of vesicular GATs (VGAT). Hypoosmotic stimulation in vivo reduced the number of VGAT-expressing neurons, and increased co-localisation and molecular association of VGAT with glial fibrillary acidic protein that increased significantly by 10 min. By 30 min, neuronal VGAT labelling was partially restored, and astrocytic VGAT was relocated to the ventral portion while it decreased in the somatic zone of the SON. Thus, synergistic astrocytic and neuronal GABAergic inhibition could ensure that vasopressin neuron firing is only transiently suppressed under hypoosmotic conditions.

Hyposmolality differentially and spatiotemporally modulates levels of glutamine synthetase and serine racemase in rat supraoptic nucleus

Prolonged hyposmotic challenge (HOC) has a dual effect on vasopressin (VP) secretion [Yagil and Sladek (1990) Am J Physiol 258(2 Pt 2):R492-R500]. We describe an electrophysiological correlate of this phenomenon, whereby in vitro HOC transiently reduced the firing activity of VP neurons within the supraoptic nucleus of brain slices, which was followed by a rebound increase of their activity; this was paralleled by changes in the level of proteins relevant to astroglia-neuronal interactions. Hence, in vitro HOC transiently (at 5 min) increased the level of astrocyte-specific glial fibrillary acidic protein (GFAP), which then declined to control or base level (at 20 min); this was blocked by the gliotoxin L-aminoadipic acid, but not by tetanus toxin, which was used to inhibit neurotransmission. Similarly, in vivo HOC led to changes in GFAP level, which after an early increase (10 min) returned to normal (30 min). Immunoassays revealed that neuronal, but not astrocytic, expression of serine racemase (SR) was increased at the late stage of HOC in vivo, whereas at an early stage there was a transient increase in level of the astrocyte-specific glutamine synthetase (GS). Furthermore, there was an increased molecular association between GFAP and GS at 10 min, whereas SR increased its association with the neuronal nuclear antigen NeuN at 30 min. These results suggest that the dual effect of HOC on VP neuronal secretion/activity could be related to metabolic/signaling changes in astrocytes (glutamate-glutamine conversion) and neurons (D-serine synthesis/ammonia production), which may account for the rebound in VP neuronal activity, presumably by promoting the activation of neuronal glutamate receptors.

Staying put or leaving home: endocrine, neuroendocrine and behavioral consequences in male African striped mice

Social flexibility occurs when individuals of both sexes can change their social and reproductive tactics, which in turn can influence the social system of an entire population. However, little is known regarding the extent to which individuals of socially flexible species vary in their social behavior and in the underlying physiological mechanisms that support different social tactics. The present study in African striped mice modeled in captivity three male tactics described from the field: (a) philopatric males remaining in the family; (b) solitary roamers; or (c) group-living breeding males. Sixteen pairs and their offspring were kept in captivity, while one male offspring from the family remained as singly housed after he reached 21 days of age. Differences in behavior, morphology, hormone and neuropeptide levels were tested, and physiological measurements were correlated with behavioral measurements. In standardized arena experiments group-living males (philopatrics and breeders) were significantly more aggressive than singly housed males, in agreement with previous data suggesting that group-living, but not roaming males, are territorial. Philopatric males showed signs of reproductive suppression, small testes, lower testosterone and higher corticosterone levels than their singly housed brothers. Higher levels of arginine vasopressin (AVP) were measured in the PVN and BNST of singly housed males compared to group-living males. Based on these findings we hypothesize that roamers are physiologically primed, and capable, if the opportunity to mate arises, to release AVP, form social bonds and become territorial, thus quickly adopting the tactic as breeding male which would yield a higher reproductive success.

Social rank-dependent expression of arginine vasotocin in distinct preoptic regions in male Oryzias latipes

This study examined arginine vasotocin (AVT) expression in the brains of dominant and subordinate male medaka Oryzias latipes after short- and long-term competition. High AVT expression in distinct preoptic regions was found in dominants and subordinates within minutes of encountering each other. During long-term competition, AVT expression remained high in dominants but not in subordinates.

Borderline personality disorder: current drug treatments and future prospects

Individuals with borderline personality disorder (BPD) suffer from marked affective disturbance, an unstable sense of self, difficulty in interpersonal relationships and heightened impulsivity, leading to high rates of self-harm and suicide. Patients are often refractory to treatment and are at high risk for acute or dangerous presentations, with a serious impact on mental health services. There has been much debate on the effectiveness of pharmacotherapy in treating different facets of the psychopathology of the disorder. Several guidelines recommend the use of antidepressant agents, mood stabilizers for affective dysregulation and impulsive-behavioural dyscontrol, and antipsychotics for cognitive-perceptual symptoms. However, concerns have recently been raised regarding the strength of evidence for these treatment recommendations in BPD. Here, we review the evidence for efficacy of the main psychotropic medications used in BPD, drawing, in particular, on evidence from randomized controlled trials and meta-analyses. Overall, meta-analysis provides little evidence to support the use of antidepressant medication in BPD outside episodes of major depression. However, there is evidence for the use of both mood stabilizers and antipsychotic medications for the treatment of specific aspects of the disorder. Most existing studies have been conducted on small numbers of patients, and there is a requirement for further large-scale trials to substantiate these findings. In addition, given the limitations of current pharmacological treatment of BPD, there is a pressing need to investigate potential new therapeutic targets, including neuropeptides, such as the opioids and vasopressin, and drugs targeted at ameliorating the biological effects of early life stress.

Vasopressin inhibits LTP in the CA2 mouse hippocampal area

Growing evidence points to vasopressin (AVP) as a social behavior regulator modulating various memory processes and involved in pathologies such as mood disorders, anxiety and depression. Accordingly, AVP antagonists are actually envisaged as putative treatments. However, the underlying mechanisms are poorly characterized, in particular the influence of AVP on cellular or synaptic activities in limbic brain areas involved in social behavior. In the present study, we investigated AVP action on the synapse between the entorhinal cortex and CA2 hippocampal pyramidal neurons, by using both field potential and whole-cell recordings in mice brain acute slices. Short application (1 min) of AVP transiently reduced the synaptic response, only following induction of long-term potentiation (LTP) by high frequency stimulation (HFS) of afferent fibers. The basal synaptic response, measured in the absence of HFS, was not affected. The Schaffer collateral-CA1 synapse was not affected by AVP, even after LTP, while the Schaffer collateral-CA2 synapse was inhibited. Although investigated only recently, this CA2 hippocampal area appears to have a distinctive circuitry and a peculiar role in controlling episodic memory. Accordingly, AVP action on LTP-increased synaptic responses in this limbic structure may contribute to the role of this neuropeptide in controlling memory and social behavior.

Effects of Chronic Central Arginine Vasopressin (AVP) on Maternal Behavior in Chronically Stressed Rat Dams

Exposure of mothers to chronic stressors during pregnancy or the postpartum period often leads to the development of depression, anxiety, or other related mood disorders. The adverse effects of mood disorders are often mediated through maternal behavior and recent work has identified arginine vasopressin (AVP) as a key neuropeptide hormone in the expression of maternal behavior in both rats and humans. Using an established rodent model that elicits behavioral and physiological responses similar to human mood disorders, this study tested the effectiveness of chronic AVP infusion as a novel treatment for the adverse effects of exposure to chronic social stress during lactation in rats. During early (day 3) and mid (day 10) lactation, AVP treatment significantly decreased the latency to initiate nursing and time spent retrieving pups, and increased pup grooming and total maternal care (sum of pup grooming and nursing). AVP treatment was also effective in decreasing maternal aggression and the average duration of aggressive bouts on day 3 of lactation. Central AVP may be an effective target for the development of treatments for enhancing maternal behavior in individuals exposed to chronic social stress.

Connectivity from OR37 expressing olfactory sensory neurons to distinct cell types in the hypothalamus

Olfactory sensory neurons (OSNs) which express a member from the OR37 subfamily of odorant receptor (OR) genes are wired to the main olfactory bulb (MOB) in a unique monoglomerular fashion; from these glomeruli an untypical connectivity into higher brain centers exists. In the present study we have investigated by DiI and transsynaptic tracing approaches how the connection pattern from these glomeruli into distinct hypothalamic nuclei is organized. The application of DiI onto the ventral domain of the bulb which harbors the OR37 glomeruli resulted in the labeling of fibers within the paraventricular nucleus (PVN) and supraoptic nucleus (SO) of the hypothalamus; some of these fibers were covered with varicose-like structures. No DiI-labeled cell somata were detectable in these nuclei. The data indicate that projection neurons which originate in the OR37 region of the MOB form direct connections into these nuclei. The cells that were labeled by the transsynaptic tracer WGA in these nuclei were further characterized. Their distribution pattern in the paraventricular nucleus was reminiscent of cells which produce distinct neuropeptides. Double labeling experiments confirmed that they contained vasopressin, but not the related neuropeptide oxytocin. Morphological analysis revealed that they comprise of magno- and parvocellular cells. A comparative investigation of the WGA-positive cells in the SO demonstrated that these were vasopressin-positive, as well, whereas oxytocin-producing cells of this nucleus also contained no transsynaptic tracer. Together, the data demonstrates a connectivity from OR37 expressing sensory neurons to distinct hypothalamic neurons with the same neuropeptide content.

Cell-type specific expression of the vasopressin gene analyzed by AAV mediated gene delivery of promoter deletion constructs into the rat SON in vivo

The magnocellular neurons (MCNs) in the supraoptic nucleus (SON) of the hypothalamus selectively express either oxytocin (Oxt) or vasopressin (Avp) neuropeptide genes. In this paper we examine the cis-regulatory domains in the Avp gene promoter that are responsible for its cell-type specific expression. AAV vectors that contain various Avp gene promoter deletion constructs using EGFP as the reporter were stereotaxically injected into the rat SON. Two weeks following the injection immunohistochemical assays of EGFP expression from these constructs were done to determine whether the expressed EGFP reporter co-localizes with either the Oxt- or Avp-immunoreactivity in the MCNs. The results identify three major enhancer domains located at −2.0 to −1.5 kbp, −1.5 to −950 bp, and −950 to −543 bp in the Avp gene promoter that regulate the expression in Avp MCNs. The results also show that cell–type specific expression in Avp MCNs is maintained in constructs containing at least 288 bp of the promoter region upstream of the transcription start site, but this specificity is lost at 116 bp and below. Based on these data, we hypothesize that the −288 bp to −116 bp domain contains an Avp MCN specific activator and a possible repressor that inhibits expression in Oxt-MCNs, thereby leading to the cell-type specific expression of the Avp gene only in the Avp-MCNs.

The behavioral, anatomical and pharmacological parallels between social attachment, love and addiction

RATIONALE

Love has long been referred to as an addiction in literature and poetry. Scientists have often made comparisons between social attachment processes and drug addiction, and it has been suggested that the two may share a common neurobiological mechanism. Brain systems that evolved to govern attachments between parents and children and between monogamous partners may be the targets of drugs of abuse and serve as the basis for addiction processes.

OBJECTIVES

Here, we review research on drug addiction in parallel with research on social attachments, including parent-offspring attachments and social bonds between mating partners. This review focuses on the brain regions and neurochemicals with the greatest overlap between addiction and attachment and, in particular, the mesolimbic dopamine (DA) pathway.

RESULTS

Significant overlap exists between these two behavioral processes. In addition to conceptual overlap in symptomatology, there is a strong commonality between the two domains regarding the roles and sites of action of DA, opioids, and corticotropin-releasing factor. The neuropeptides oxytocin and vasopressin are hypothesized to integrate social information into attachment processes that is not present in drug addiction.

CONCLUSIONS

Social attachment may be understood as a behavioral addiction, whereby the subject becomes addicted to another individual and the cues that predict social reward. Understandings from both fields may enlighten future research on addiction and attachment processes.

Synaptic innervation to rat hippocampus by vasopressin-immuno-positive fibres from the hypothalamic supraoptic and paraventricular nuclei

The neuropeptide arginine vasopressin (AVP) exerts a modulatory role on hippocampal excitability through vasopressin V(1A) and V(1B) receptors. However, the origin and mode of termination of the AVP innervation of the hippocampus remain unknown. We have used light and electron microscopy to trace the origin, distribution and synaptic relationships of AVP-immuno-positive fibres and nerve terminals in the rat hippocampus. Immuno-positive fibres were present in all areas (CA1-3, dentate gyrus) of the whole septo-temporal extent of the hippocampus; they had the highest density in the CA2 region, strongly increasing in density towards the ventral hippocampus. Two types of fibres were identified, both establishing synaptic junctions. Type A had large varicosities packed with immuno-positive large-granulated peptidergic vesicles and few small clear vesicles forming type I synaptic junctions with pyramidal neuron dendrites, dendritic spines and with axonal spines. Type B had smaller varicosities containing mostly small clear vesicles and only a few large-granulated vesicles and established type II synaptic junctions mainly with interneuron dendrites. The AVP-positive axons in stratum oriens appeared to follow and contact metabotropic glutamate receptor 1α (mGluR1α)-immuno-positive interneuron dendrites. Fluoro-Gold injection into the hippocampus revealed retrogradely labelled AVP-positive somata in hypothalamic supraoptic and paraventricular nuclei. Hypothalamo-hippocampal AVP-positive axons entered the hippocampus mostly through a ventral route, also innervating the amygdala and to a lesser extent through the dorsal fimbria fornix, in continuation of the septal AVP innervation. Thus, it appears the AVP-containing neurons of the magnocellular hypothalamic nuclei serve as important sources for hippocampal AVP innervation, although the AVP-expressing neurons located in amygdala and bed nucleus of the stria terminalis reported previously may also contribute.

Vasopressin V1a and V1b Receptors: From Molecules to Physiological Systems

The neurohypophysial hormone arginine vasopressin (AVP) is essential for a wide range of physiological functions, including water reabsorption, cardiovascular homeostasis, hormone secretion, and social behavior. These and other actions of AVP are mediated by at least three distinct receptor subtypes: V1a, V1b, and V2. Although the antidiuretic action of AVP and V2 receptor in renal distal tubules and collecting ducts is relatively well understood, recent years have seen an increasing understanding of the physiological roles of V1a and V1b receptors. The V1a receptor is originally found in the vascular smooth muscle and the V1b receptor in the anterior pituitary. Deletion of V1a or V1b receptor genes in mice revealed that the contributions of these receptors extend far beyond cardiovascular or hormone-secreting functions. Together with extensively developed pharmacological tools, genetically altered rodent models have advanced the understanding of a variety of AVP systems. Our report reviews the findings in this important field by covering a wide range of research, from the molecular physiology of V1a and V1b receptors to studies on whole animals, including gene knockout/knockdown studies.

Naturally occurring variation in vasopressin immunoreactivity is associated with maternal behavior in female Peromyscus mice

In many mammals, species-appropriate social behavior is necessary for an individual's ability to survive and reproduce. In the present study, we examined whether arginine-vasopressin (AVP) pathways that have been associated with social behavior differed between two closely related species of Peromyscus mice with different patterns of maternal behavior. We also tested whether individual levels of AVP-immunoreactive staining (AVP-ir) were associated with individual levels of maternal behavior as measured using a composite score consisting of huddling, nursing, grooming and time spent inside the nest (HNGI score). In addition, we examined whether these associations between vasopressin and behavior differed between species. Females from the highly biparental species, California mice, displayed higher AVP-ir in the bed nucleus of the stria terminalis (BNST), which corresponded with a higher level of nest building and a higher HNGI score than was found in the less parental white-footed mice. The HNGI score was positively associated with AVP-ir in the medial amygdala in female California mice but not white-footed mice. Finally, we examined whether AVP-ir in these pathways varied based on the species-specific rearing environments by reciprocally cross-fostering California mice and white-footed mice. In contrast to previous research with male California mice, cross-fostering itself had no effect on maternal behavior or any consistent effect on AVP-ir staining in brain areas such as the BNST and associated brain areas. This suggests that there is little plasticity in maternal behavior and that the underlying AVP system in females does not respond to the postnatal environment provided by the parents. The positive associations between maternal behavior and AVP-ir indicate that AVP may regulate maternal behavior despite the lack of plasticity in AVP and maternal behavior.

Circadian pacemaker in the suprachiasmatic nuclei of teleost fish revealed by rhythmic period2 expression

In mammals, the role of the suprachiasmatic nucleus (SCN) as the primary circadian clock that coordinates the biological rhythms of peripheral oscillators is well known. However, in teleosts, it remains unclear whether the SCN also functions as a circadian pacemaker. We used in situ hybridization (ISH) techniques to demonstrate that the molecular clock gene, per2, is expressed in the SCN of flounder (Paralichthys olivaceus) larvae during the day and down-regulated at night, demonstrating that a circadian pacemaker exists in the SCN of this teleost. The finding that per2 expression in the SCN was also observed in the amberjack (Seriola dumerili), but not in medaka (Oryzias latipes), implies that interspecific variation exists in the extent to which the SCN controls the circadian rhythms of fish species, presumably reflecting their lifestyle. Rhythmic per2 expression was also detected in the pineal gland and pituitary, and aperiodic per2 expression was observed in the habenula, which is known to exhibit circadian rhythms in rodents. Since the ontogeny of per2 expression in the brain of early flounder larvae can be monitored by whole mount ISH, it is possible to investigate the effects of drugs and environmental conditions on the functional development of circadian clocks in the brain of fish larvae. In addition, flounder would be a good model for understanding the rhythmicity of marine fish. Our findings open a new frontier for investigating the role of the SCN in teleost circadian rhythms.

Plasma vasopressin and interpersonal functioning

The neuropeptide vasopressin has traditionally been associated with vasoconstriction and water reabsorption by the kidneys. However, data from experimental animal studies also implicate vasopressin in social bonding processes. Preliminary work suggests that vasopressin also plays a role in social behaviors in humans. The goal of this cross-sectional study was to evaluate associations among plasma vasopressin and self-reported interpersonal functioning in a sample of married couples. During a 24-h admission to a hospital-based research unit, 37 couples completed measures of interpersonal functioning and provided blood samples for neuropeptide analyses. Results showed that vasopressin was associated with markers of interpersonal functioning, but not with general psychological distress. Specifically, greater plasma vasopressin levels were related to a larger social network, fewer negative marital interactions, less attachment avoidance, more attachment security, and marginally greater spousal social support. These results indicate that vasopressin is likely implicated in different relationship maintenance processes in humans.

Induction of arginine vasopressin-enhanced green fluorescent protein expression in the locus coeruleus following kainic acid-induced seizures in rats

Seizure causes autonomic, neuroendocrine and stress responses. We examined the effects of kainic acid (KA)-induced seizures on the expression of the arginine vasopressin (AVP)-enhanced green fluorescent protein (eGFP) in the locus coeruleus (LC), an area known to contain noradrenergic cells, in AVP-eGFP transgenic male and female rats, with the rationale to identify stressors which induce AVP synthesis in the LC. Subcutaneous (s.c.) administration of KA caused a progressive development of seizure behavior within 24 h. AVP-eGFP fluorescence in the LC was detected 6, 24, and 48 h and 1 week after administration of KA (12 mg/kg). From a nearly undetectable level, it reached a maximum at 48 h after s.c. administration of KA and returned to the basal levels after 2 weeks. AVP-eGFP fluorescence in the LC after s.c. administration of KA was significantly reduced by the pretreatment with MK-801 (nonselective N-methyl-D-aspartate (NMDA) receptor antagonist). In the KA-administered rats, immunohistochemistry for tyrosine hydroxylase (TH) revealed that the eGFP fluorescence was co-localized with TH-immuno-reactivity in the LC. These results suggest that the synthesis of AVP-eGFP is potentially up-regulated in noradrenergic neurons in the LC after KA-induced seizures through the activation of NMDA receptors.

The nonpeptide oxytocin receptor agonist WAY 267,464: receptor-binding profile, prosocial effects and distribution of c-Fos expression in adolescent rats

Previous research suggests that the nonpeptide oxytocin receptor (OTR) agonist WAY 267,464 may only partly mimic the effects of oxytocin in rodents. The present study further explored these differences and related them to OTR and vasopressin 1a receptor (V(1a) R) pharmacology and regional patterns of c-Fos expression. Binding data for WAY 267,464 and oxytocin were obtained by displacement binding assays on cellular membranes, while functional receptor data were generated by luciferase reporter assays. For behavioural testing, adolescent rats were tested in a social preference paradigm, the elevated plus-maze (EPM) and for locomotor activity changes following WAY 267,464 (10 and 100 mg/kg, i.p.) or oxytocin (0.1 and 1 mg/kg, i.p.). The higher doses were also examined for their effects on regional c-Fos expression. Results showed that WAY 267,464 had higher affinity (K(i) ) at the V(1a) R than the OTR (113 versus 978 nm). However, it had no functional response at the V(1a) R and only a weak functional effect (EC(50) ) at the OTR (881 nm). This suggests WAY 267,464 is an OTR agonist with weak affinity and a possible V(1a) R antagonist. Oxytocin showed high binding at the OTR (1.0 nm) and V(1a) R (503 nm), with a functional EC(50) of 9.0 and 59.7 nm, respectively, indicating it is a potent OTR agonist and full V(1a) R agonist. WAY 267,464 (100 mg/kg), but not oxytocin, significantly increased the proportion of time spent with a live rat, over a dummy rat, in the social preference test. Neither compound affected EPM behaviour, whereas the higher doses of WAY 267,464 and oxytocin suppressed locomotor activity. WAY 267,464 and oxytocin produced similar c-Fos expression in the paraventricular hypothalamic nucleus, central amygdala, lateral parabrachial nucleus and nucleus of the solitary tract, suggesting a commonality of action at the OTR with the differential doses employed. However, WAY 267,464 caused greater c-Fos expression in the medial amygdala and the supraoptic nucleus than oxytocin, and lesser effects in the locus coeruleus. Overall, our results confirm the differential effects of WAY 267,464 and oxytocin and suggest that this may reflect contrasting actions of WAY 267,464 and oxytocin at the V(1a) R. Antagonism of the V(1a) R by WAY 267,464 could underlie some of the prosocial effects of this drug either through a direct action or through disinhibition of oxytocin circuitry that is subject to vasopressin inhibitory influences.

Sexually dimorphic effects of a prenatal immune challenge on social play and vasopressin expression in juvenile rats

Background

Infectious diseases and inflammation during pregnancy increase the offspring’s risk for behavioral disorders. However, how immune stress affects neural circuitry during development is not well known. We tested whether a prenatal immune challenge interferes with the development of social play and with neural circuits implicated in social behavior.

Methods

Pregnant rats were given intraperitoneal injections of the bacterial endotoxin lipopolysaccharide (LPS – 100 μg /kg) or saline on the 15th day of pregnancy. Offspring were tested for social play behaviors between postnatal days 26–40. Brains were harvested on postnatal day 45 and processed for arginine vasopressin (AVP) mRNA in situ hybridization.

Results

In males, LPS treatment reduced the frequency of juvenile play behavior and reduced AVP mRNA expression in the medial amygdala and bed nucleus of the stria terminalis. These effects were not found in females. LPS treatment did not change AVP mRNA expression in the suprachiasmatic nucleus, paraventricular nucleus, or supraoptic nucleus of either sex, nor did it affect the sex difference in the size of the sexually dimorphic nucleus of the preoptic area.

Conclusions

Given AVP’s central role in regulating social behavior, the sexually dimorphic effects of prenatal LPS treatment on male AVP mRNA expression may contribute to the sexually dimorphic effect of LPS on male social play and may, therefore, increase understanding of factors that contribute to sex differences in social psychopathology.

Oxytocin and vasopressin are dysregulated in Williams Syndrome, a genetic disorder affecting social behavior

The molecular and neural mechanisms regulating human social-emotional behaviors are fundamentally important but largely unknown; unraveling these requires a genetic systems neuroscience analysis of human models. Williams Syndrome (WS), a condition caused by deletion of ∼28 genes, is associated with a gregarious personality, strong drive to approach strangers, difficult peer interactions, and attraction to music. WS provides a unique opportunity to identify endogenous human gene-behavior mechanisms. Social neuropeptides including oxytocin (OT) and arginine vasopressin (AVP) regulate reproductive and social behaviors in mammals, and we reasoned that these might mediate the features of WS. Here we established blood levels of OT and AVP in WS and controls at baseline, and at multiple timepoints following a positive emotional intervention (music), and a negative physical stressor (cold). We also related these levels to standardized indices of social behavior. Results revealed significantly higher median levels of OT in WS versus controls at baseline, with a less marked increase in AVP. Further, in WS, OT and AVP increased in response to music and to cold, with greater variability and an amplified peak release compared to controls. In WS, baseline OT but not AVP, was correlated positively with approach, but negatively with adaptive social behaviors. These results indicate that WS deleted genes perturb hypothalamic-pituitary release not only of OT but also of AVP, implicating more complex neuropeptide circuitry for WS features and providing evidence for their roles in endogenous regulation of human social behavior. The data suggest a possible biological basis for amygdalar involvement, for increased anxiety, and for the paradox of increased approach but poor social relationships in WS. They also offer insight for translating genetic and neuroendocrine knowledge into treatments for disorders of social behavior.

Effect of arginine vasopressin on the behavioral activity in the behavior despair depression rat model

Arginine vasopressin (AVP), a nonapeptide posterior hormone of the pituitary, is mainly synthesized and secreted in the hypothalamic paraventricular nucleus (PVN) and supraoptic nucleus (SON). Large numbers of studies have reported that AVP plays a role in depression. The present study was to investigate by which level, brain or periphery, AVP affects the behavioral activity in the behavior despair depression rat model. The results showed that (1) either forced swimming or tail suspension significantly increased AVP concentration not only in the brain (PVN, SON, frontal of cortex, hippocampus, amygdala, lumber spinal cord) but also in the periphery (posterior pituitary and serum); (2) intraventricular injection (icv) of AVP decreased the animal immobility time, whereas V₁ receptor antagonist d(CH₂)₅Tyr(Me)AVP (icv) increased the animal immobility time in a dose-dependent manner not only in FST but also in TST, but the V₂ receptor antagonist d(CH₂)₅[D-Ile, Ile, Ala-NH₉]AVP did not change the animal immobility time in FST or TST; (3) V₁, not V₂ receptor antagonist could inhibit the animal immobility time decrease induced by AVP (icv); (4) neither AVP nor its receptor antagonist (including V₁ and V₂ receptor antagonist) influenced the animal immobility time in both FST and TST. The data suggested that AVP in the brain rather than the periphery played a role in the behavior despair depression by V₁, not V₂ receptors, which behavior despair might have a positive feedback effect on central AVP and blood AVP might have a negative feedback on central AVP in the depressive process.

The animal and human neuroendocrinology of social cognition, motivation and behavior

Extensive animal and recent human research have helped inform neuroendocrinological models of social cognition, motivation and behavior. In this review, we first summarize important findings regarding oxytocin, arginine vasopressin and testosterone in the domains of affiliation, social cognition, aggression and stress/anxiety. We then suggest ways in which human research can continue to profit from animal research, particularly by exploring the interactive nature of neuromodulatory effects at neurochemical, organismic and contextual levels. We further propose methods inspired by the animal literature for the ecologically valid assessment of affiliative behavior in humans. We conclude with suggestions for how human research could advance by directly assessing specific social cognitive and motivational mechanisms as intermediate variables. We advocate a more comprehensive look at the distinct networks identified by social neuroscience and the importance of a motivational state, in addition to approach and avoidance, associated with quiescence and homeostatic regulation.

Oxytocin and vasopressin genes are significantly associated with schizophrenia in a large Arab-Israeli pedigree

We have previously studied the genetics of schizophrenia in a large inbred Arab-Israeli pedigree and found evidence for linkage on chromosome 20p13. This locus harbours four strong candidate genes for schizophrenia: atractin (ATRN), pantonate-kinase2 (PANK2), oxytocin (OXT) and arginine-vasopressin (AVP). In this study we further explored the association of these genes with schizophrenia in the pedigree and searched for the disease-causing variants. A mutation screening of affected individuals from the pedigree was performed by using intensive sequencing in these four genes of interest. Then, we studied the prevalence of the identified variants in all family members (n=56) as well as in Arab-Israeli nuclear families (n=276) and a Jewish case-control sample (n=545). We also studied the possible functional role of these variants by examining their association with gene expression in the brain (n=104). We identified seven genetic variants in the OXT-AVP cluster in affected individuals from the pedigree. Three of these variants were significantly associated with schizophrenia in this pedigree. A 7-SNP haplotype was also significantly associated with disease. We found significant association of some of these variants in the two samples from the general population. Expression data analysis showed a possible functional role of two of these variants in regulation of gene expression. Involvement of OXT and AVP in the aetiology of schizophrenia has been suggested in the past. This study demonstrates, for the first time, a significant genetic association of these neuropeptides with schizophrenia and strongly supports this hypothesis.

Oxytocin and vasopressin agonists and antagonists as research tools and potential therapeutics

We recently reviewed the status of peptide and nonpeptide agonists and antagonists for the V(1a), V(1b) and V(2) receptors for arginine vasopressin (AVP) and the oxytocin receptor for oxytocin (OT). In the present review, we update the status of peptides and nonpeptides as: (i) research tools and (ii) therapeutic agents. We also present our recent findings on the design of fluorescent ligands for V(1b) receptor localisation and for OT receptor dimerisation. We note the exciting discoveries regarding two novel naturally occurring analogues of OT. Recent reports of a selective VP V(1a) agonist and a selective OT agonist point to the continued therapeutic potential of peptides in this field. To date, only two nonpeptides, the V(2) /V(1a) antagonist, conivaptan and the V(2) antagonist tolvaptan have received Food and Drug Administration approval for clinical use. The development of nonpeptide AVP V(1a), V(1b) and V(2) antagonists and OT agonists and antagonists has recently been abandoned by Merck, Sanofi and Pfizer. A promising OT antagonist, Retosiban, developed at Glaxo SmithKline is currently in a Phase II clinical trial for the prevention of premature labour. A number of the nonpeptide ligands that were not successful in clinical trials are proving to be valuable as research tools. Peptide agonists and antagonists continue to be very widely used as research tools in this field. In this regard, we present receptor data on some of the most widely used peptide and nonpeptide ligands, as a guide for their use, especially with regard to receptor selectivity and species differences.

Sculpting the hippocampus from within: stress, spines, and CRH

Learning and memory processes carried out within the hippocampus are influenced by stress in a complex manner, and the mechanisms by which stress modulates the physiology of the hippocampus are not fully understood. This review addresses how the production and release of the neuropeptide corticotropin-releasing hormone (CRH) within the hippocampus during stress influences neuronal structure and hippocampal function. CRH functions in the contexts of acute and chronic stresses taking place during development, adulthood and aging. Current challenges are to uncover how the dynamic actions of CRH integrate with the well-established roles of adrenal-derived steroid stress hormones to shape the cognitive functions of the hippocampus in response to stress.

Variation in maternal and anxiety-like behavior associated with discrete patterns of oxytocin and vasopressin 1a receptor density in the lateral septum

The relationship between anxiety and maternal behavior has been explored across species using a variety of approaches, yet there is no clear consensus on the nature or direction of this relationship. In the current study, we have assessed stable individual differences in anxiety-like behavior in a large cohort (n=57) of female F2 hybrid mice. Using open-field behavior as a continuous and categorical (high vs. low) measure we examined the relationship between the anxiety-like behavior of virgin F2 females and the subsequent maternal behavior of these females. In addition, we quantified oxytocin (OTR) and vasopressin (V1a) receptor density within the lateral septum to determine the possible correlation with anxiety-like and maternal behavior. We find that, though activity levels within the open-field do predict latency to engage in pup retrieval, anxiety-like measures on this test are otherwise not associated with subsequent maternal behavior. OTR density in the dorsal lateral septum was found to be negatively correlated with activity levels in the open-field and positively correlated with frequency of nursing behavior. V1a receptor density was significantly correlated with postpartum licking/grooming of pups. Though we do not find support for the hypothesis that individual differences in trait anxiety predict variation in maternal behavior, we do find evidence for the role of OTR and V1a receptors in predicting maternal behavior in mice and suggest possible methodological issues (such as distinguishing between trait and state anxiety) that will be a critical consideration for subsequent studies of the anxiety-maternal behavior relationship. This article is part of a Special Issue entitled Oxytocin, Vasopressin, and Social Behavior.

The vasopressin 1b receptor and the neural regulation of social behavior

To date, much of the work in rodents implicating vasopressin (Avp) in the regulation of social behavior has focused on its action via the Avp 1a receptor (Avpr1a). However, there is mounting evidence that the Avp 1b receptor (Avpr1b) also plays a significant role in Avp's modulation of social behavior. The Avpr1b is heavily expressed on the anterior pituitary cortiocotrophs where it acts as an important modulator of the endocrine stress response. In the brain, the Avpr1b is prominent in the CA2 region of the hippocampus, but can also be found in areas such as the paraventricular nucleus of the hypothalamus and the olfactory bulb. Studies that have employed genetic knockouts or pharmacological manipulation of the Avpr1b point to the importance of central Avpr1b in the modulation of social behavior. However, there continues to be a knowledge gap in our understanding of where in the brain this is occurring, as well as how and if the central actions of Avp acting via the Avpr1b interact with the stress axis. In this review we focus on the genetic and pharmacological studies that have implicated the Avpr1b in the neural regulation of social behaviors, including social forms of aggressive behavior, social memory, and social motivation. This article is part of a Special Issue entitled Oxytocin, Vasopressin, and Social Behavior.

Human neuroimaging of oxytocin and vasopressin in social cognition

The neuropeptides oxytocin and vasopressin have increasingly been identified as modulators of human social behaviors and associated with neuropsychiatric disorders characterized by social dysfunction, such as autism. Identifying the human brain regions that are impacted by oxytocin and vasopressin in a social context is essential to fully characterize the role of oxytocin and vasopressin in complex human social cognition. Advances in human non-invasive neuroimaging techniques and genetics have enabled scientists to begin to elucidate the neurobiological basis of the influence of oxytocin and vasopressin on human social behaviors. Here we review the findings to-date from investigations of the acute and chronic effects of oxytocin and vasopressin on neural activity underlying social cognitive processes using "pharmacological fMRI" and "imaging genetics", respectively. This article is part of a Special Issue entitled Oxytocin, Vasopressin, and Social Behavior.

Oxytocin receptor density is associated with male mating tactics and social monogamy

Despite its well-described role in female affiliation, the influence of oxytocin on male pairbonding is largely unknown. However, recent human studies indicate that this nonapeptide has a potent influence on male behaviors commonly associated with monogamy. Here we investigated the distribution of oxytocin receptors (OTR) throughout the forebrain of the socially monogamous male prairie vole (Microtus ochrogaster). Because males vary in both sexual and spatial fidelity, we explored the extent to which OTR predicted monogamous or non-monogamous patterns of space use, mating success and sexual fidelity in free-living males. We found that monogamous males expressed higher OTR density in the nucleus accumbens than non-monogamous males, a result that mirrors species differences in voles with different mating systems. OTR density in the posterior portion of the insula predicted mating success. Finally, OTR in the hippocampus and septohippocampal nucleus, which are nuclei associated with spatial memory, predicted patterns of space use and reproductive success within mating tactics. Our data highlight the importance of oxytocin receptor in neural structures associated with pairbonding and socio-spatial memory in male mating tactics. The role of memory in mating systems is often neglected, despite the fact that mating tactics impose an inherently spatial challenge for animals. Identifying mechanisms responsible for relating information about the social world with mechanisms mediating pairbonding and mating tactics is crucial to fully appreciate the suite of factors driving mating systems. This article is part of a Special Issue entitled Oxytocin, Vasopressin, and Social Behavior.

Both oxytocin and vasopressin are mediators of maternal care and aggression in rodents: from central release to sites of action

In the mammalian peripartum period, the activity of both the brain oxytocin and vasopressin system is elevated as part of the physiological adaptations occurring in the mother. This is reflected by increased expression and intracerebral release of oxytocin and vasopressin, as well as increased neuropeptide receptor expression and binding. In this review we discuss the functional role of the brain oxytocin and vasopressin system in the context of maternal behavior, specifically maternal care and maternal aggression in rodents. In order to enable the identification of significant and peptide-specific contributions to the display of maternal behavior, various complementary animal models of maternal care and/or maternal aggression were studied, including rats selectively bred for differences in anxiety-related behavior (HAB and LAB dams), monitoring of local neuropeptide release during ongoing maternal behavior, and local pharmacological or genetic manipulations of the neuropeptide systems. The medial preoptic area was identified as a major site for oxytocin- and vasopressin-mediated maternal care. Furthermore, both oxytocin and vasopressin release and receptor activation in the central amygdala and the bed nucleus of the stria terminalis play an important role for maternal aggression. This article is part of a Special Issue entitled Oxytocin, Vasopressin, and Social Behavior.

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.

Cell-type specific oxytocin gene expression from AAV delivered promoter deletion constructs into the rat supraoptic nucleus in vivo

The magnocellular neurons (MCNs) in the hypothalamus selectively express either oxytocin (OXT) or vasopressin (AVP) neuropeptide genes, a property that defines their phenotypes. Here we examine the molecular basis of this selectivity in the OXT MCNs by stereotaxic microinjections of adeno-associated virus (AAV) vectors that contain various OXT gene promoter deletion constructs using EGFP as the reporter into the rat supraoptic nucleus (SON). Two weeks following injection of the AAVs, immunohistochemical assays of EGFP expression from these constructs were done to determine whether the EGFP reporter co-localizes with either the OXT- or AVP-immunoreactivity in the MCNs. The results show that the key elements in the OT gene promoter that regulate the cell-type specific expression the SON are located -216 to -100 bp upstream of the transcription start site. We hypothesize that within this 116 bp domain a repressor exists that inhibits expression specifically in AVP MCNs, thereby leading to the cell-type specific expression of the OXT gene only in the OXT MCNs.

Forensic aspects of water intoxication: four case reports and review of relevant literature

Water intoxication (WI) is a rare condition that originates from over-consumption of water, with a potentially fatal outcome. Increased water intake (polydipsia) is followed by urination of high amount of diluted urine (polyuria) which are the main initial symptoms of WI. We present four case reports of WI. Two of them are unusual pediatric clinical cases using medical documentation and police case files, one of which is related to child abuse, and the other to a psychiatric disorder. The other two cases are fatal adult cases submitted to autopsy from a psychiatric hospital. Also, we present a diagnostic algorithm for polydipsia and polyuria before death. WI is usually seen in patients with psychiatric disorders, victims of child abuse or torture, drug abusers or it can be iatrogenically induced.

Neurobiology of sociability

Sociability consists of behaviors that bring animals together and those that keep animals apart. Remarkably, while the neural circuitry that regulates these two "faces" of sociability differ from one another, two neurohormones, oxytocin (Oxt) and vasopressin (Avp), have been consistently implicated in the regulation of both. In this chapter the the structure and function of the Oxt and Avp systems, the ways in which affiliative and aggressive behavior are studied and the roles of Oxt and Avp in the regulation of sociability will be briefly reviewed. Finally, work implicating Oxt and Avp in sociability in humans, with a focus on neuropsychiatric disorders will be highlighted.

Acute effects of steroid hormones and neuropeptides on human social-emotional behavior: a review of single administration studies

Steroids and peptides mediate a diverse array of animal social behaviors. Human research is restricted by technical-ethical limitations, and models of the neuroendocrine regulation of social-emotional behavior are therefore mainly limited to non-human species, often under the assumption that human social-emotional behavior is emancipated from hormonal control. Development of acute hormone administration procedures in human research, together with the advent of novel non-invasive neuroimaging techniques, have opened up opportunities to systematically study the neuroendocrinology of human social-emotional behavior. Here, we review all placebo-controlled single hormone administration studies addressing human social-emotional behavior, involving the steroids testosterone and estradiol, and the peptides oxytocin and vasopressin. These studies demonstrate substantial hormonal control over human social-emotional behavior and give insights into the underlying neural mechanisms. Finally, we propose a theoretical model that synthesizes detailed knowledge of the neuroendocrinology of social-emotional behavior in animals with the recently gained data from humans described in our review.

Probing the production of amidated peptides following genetic and dietary copper manipulations

Amidated neuropeptides play essential roles throughout the nervous and endocrine systems. Mice lacking peptidylglycine α-amidating monooxygenase (PAM), the only enzyme capable of producing amidated peptides, are not viable. In the amidation reaction, the reactant (glycine-extended peptide) is converted into a reaction intermediate (hydroxyglycine-extended peptide) by the copper-dependent peptidylglycine-α-hydroxylating monooxygenase (PHM) domain of PAM. The hydroxyglycine-extended peptide is then converted into amidated product by the peptidyl-α-hydroxyglycine α-amidating lyase (PAL) domain of PAM. PHM and PAL are stitched together in vertebrates, but separated in some invertebrates such as Drosophila and Hydra. In addition to its luminal catalytic domains, PAM includes a cytosolic domain that can enter the nucleus following release from the membrane by γ-secretase. In this work, several glycine- and hydroxyglycine-extended peptides as well as amidated peptides were qualitatively and quantitatively assessed from pituitaries of wild-type mice and mice with a single copy of the Pam gene (PAM^+/−) via liquid chromatography-mass spectrometry-based methods. We provide the first evidence for the presence of a peptidyl-α-hydroxyglycine in vivo, indicating that the reaction intermediate becomes free and is not handed directly from PHM to PAL in vertebrates. Wild-type mice fed a copper deficient diet and PAM^+/− mice exhibit similar behavioral deficits. While glycine-extended reaction intermediates accumulated in the PAM^+/− mice and reflected dietary copper availability, amidated products were far more prevalent under the conditions examined, suggesting that the behavioral deficits observed do not simply reflect a lack of amidated peptides.