Oxytocinergic regulation of endogenous as well as drug-induced mood

Genetic-epigenetic-neuropeptide associations in mood and anxiety disorders: Toward personalized medicine

Mood and anxiety disorders are complex psychiatric conditions shaped by the multifactorial interplay of genetic, epigenetic, and neuropeptide factors. This review aims to elucidate the intricate interactions among these factors and their potential in advancing personalized medicine. We examine the genetic underpinnings, emphasizing key heritability studies and specific gene associations. The role of epigenetics is discussed, focusing on how environmental factors can modify gene expression and contribute to these disorders. Neuropeptides, including substance P, CRF, AVP, NPY, galanin, and kisspeptin, are evaluated for their involvement in mood regulation and their potential as therapeutic targets. Additionally, we address the emerging role of the gut microbiome in modulating neuropeptide activity and its connection to mood disorders. This review integrates findings from genetic, epigenetic, and neuropeptide research, offering a comprehensive overview of their collective impact on mood and anxiety disorders. By highlighting novel insights and potential clinical applications, we underscore the importance of a multi-omics approach in developing personalized treatment strategies. Future research directions are proposed to address existing knowledge gaps and translate these findings into clinical practice. Our review provides a fresh perspective on the pathophysiology of mood and anxiety disorders, paving the way for more effective and individualized therapies.

Loss of transient receptor potential channel 5 causes obesity and postpartum depression

Hypothalamic neural circuits regulate instinctive behaviors such as food seeking, the fight/flight response, socialization, and maternal care. Here, we identified microdeletions on chromosome Xq23 disrupting the brain-expressed transient receptor potential (TRP) channel 5 (TRPC5). This family of channels detects sensory stimuli and converts them into electrical signals interpretable by the brain. Male TRPC5 deletion carriers exhibited food seeking, obesity, anxiety, and autism, which were recapitulated in knockin male mice harboring a human loss-of-function TRPC5 mutation. Women carrying TRPC5 deletions had severe postpartum depression. As mothers, female knockin mice exhibited anhedonia and depression-like behavior with impaired care of offspring. Deletion of Trpc5 from oxytocin neurons in the hypothalamic paraventricular nucleus caused obesity in both sexes and postpartum depressive behavior in females, while Trpc5 overexpression in oxytocin neurons in knock-in mice reversed these phenotypes. We demonstrate that TRPC5 plays a pivotal role in mediating innate human behaviors fundamental to survival, including food seeking and maternal care.

The entactogen 3,4-methylenedioxymethamphetamine (MDMA; ecstasy) as a treatment aid in psychotherapy and its safety concerns

The phenylethylamine, 3,4-methylenedioxymethamphetamine (MDMA, 'ecstasy'), is the prototypical example of an entactogen. Its original placement in highly restrictive drug usage categories in the US and UK, led to an inevitable restriction on MDMA neuroscience research and treatment. The dominant pharmacological effects of MDMA are its properties of release and inhibition of reuptake of amine neurotransmitter transporters for dopamine, norepinephrine, and serotonin. MDMA is an agonist of a wide range of receptors; its mood-altering effects are mediated via 5-HT2A receptors; this receptor may also mediate its effects on body temperature, analgesia, and anxiolytic properties. The mechanisms underlying MDMA's entactogenic properties of sociability and interpersonal closeness are not known but release and involvement of oxytocin, a peptide thought by some to be involved in social bonding, has been suggested. Adverse effects of MDMA are mostly transient; acute multiorgan adverse effects occurring during raves or crowded dance gatherings include dehydration, hyperthermia, seizures, rhabdomyolysis, disseminated intravascular coagulation, and acute renal failure. Deaths following MDMA taken by itself are rare compared to fatalities following coadministration with other drugs. A recent FDA-approved phase 3 clinical trial of MDMA for post-traumatic stress disorder (PTSD) led to the conclusion that MDMA-assisted therapy represents a potential breakthrough treatment meriting expedited clinical evaluation. Despite the ongoing deliberations by the FDA and EMA for approval of MDMA treatment of PTSD, the Australian Therapeutic Goods Administration (TGA) recently announced that after an evaluation of the therapeutic value, benefits, and risks of MDMA, it will permit its prescribing for the treatment of PTSD. Further examples of regulatory relaxation toward MDMA-assisted psychotherapy are underway. These include the FDA's recently approved clinical trial to assess MDMA's efficacy in the treatment of "asociality" in patients with schizophrenia and an open trial of MDMA treatment for alcohol-use disorder which showed decreased alcohol consumption. There are also ongoing studies on the little understood startle response, anxiety associated with life-threatening illness, and social anxiety in autistic adults.

Sex Differences in Tryptophan Metabolism: A Systematic Review Focused on Neuropsychiatric Disorders

Tryptophan (Tryp) is an essential amino acid and the precursor of several neuroactive compounds within the central nervous system (CNS). Tryp metabolism, the common denominator linking serotonin (5-HT) dysfunctions and neuroinflammation, is involved in several neuropsychiatric conditions, including neurological, neurodevelopmental, neurodegenerative, and psychiatric diseases. Interestingly, most of those conditions occur and progress in a sex-specific manner. Here, we explore the most relevant observations about the influence of biological sex on Tryp metabolism and its possible relation to neuropsychiatric diseases. Consistent evidence suggests that women have a higher susceptibility than men to suffer serotoninergic alterations due to changes in the levels of its precursor Tryp. Indeed, female sex bias in neuropsychiatric diseases is involved in a reduced availability of this amino acid pool and 5-HT synthesis. These changes in Tryp metabolism could lead to sexual dimorphism on the prevalence and severity of some neuropsychiatric disorders. This review identifies gaps in the current state of the art, thus suggesting future research directions. Specifically, there is a need for further research on the impact of diet and sex steroids, both involved in this molecular mechanism as they have been poorly addressed for this topic.

Anxiety and Depression: What Do We Know of Neuropeptides?

In modern society, there has been a rising trend of depression and anxiety. This trend heavily impacts the population's mental health and thus contributes significantly to morbidity and, in the worst case, to suicides. Modern medicine, with many antidepressants and anxiolytics at hand, is still unable to achieve remission in many patients. The pathophysiology of depression and anxiety is still only marginally understood, which encouraged researchers to focus on neuropeptides, as they are a vast group of signaling molecules in the nervous system. Neuropeptides are involved in the regulation of many physiological functions. Some act as neuromodulators and are often co-released with neurotransmitters that allow for reciprocal communication between the brain and the body. Most studied in the past were the antidepressant and anxiolytic effects of oxytocin, vasopressin or neuropeptide Y and S, or Substance P. However, in recent years, more and more novel neuropeptides have been added to the list, with implications for the research and development of new targets, diagnostic elements, and even therapies to treat anxiety and depressive disorders. In this review, we take a close look at all currently studied neuropeptides, their related pathways, their roles in stress adaptation, and the etiology of anxiety and depression in humans and animal models. We will focus on the latest research and information regarding these associated neuropeptides and thus picture their potential uses in the future.

Oxytocin-induced anxiogenic behavior in juvenile male rats

Oxytocin (OT) is considered beneficial to mental health owing to its anxiolytic, prosocial, and anti-stress effects; however, the adverse effects of OT have been controversial, such as its potentially anxiogenic actions. Although OT influences drug abuse and reciprocally affects vulnerability to drug use, the relationship between OT’s anxiogenic working and nicotine preference intake has not been clearly defined. To clarify this issue, the effect of acute peripheral administration of OT on anxiety and nicotine preference was investigated in juvenile male rats. Anxiogenic behaviors were noticeably increased in OT-administrated rats, with an increase in serum corticosterone levels. Moreover, increased anxiety-like behaviors and corticosterone levels were observed in the OT analog carbetocin-injected rats. In the nicotine preference test, the rats’ aversive responses to initial nicotine choice and preference were not significantly different between saline-injected and OT-injected rats. However, when administered with OT, there was a significant negative correlation between anxiety-like behavior and low-dose nicotine consumption. Collectively, these results provide evidence that acute OT exposure could induce anxiogenic behavior with corticosterone augmentation, contributing to the attenuation of nicotine preference. This suggests that both aspects of OT, as well as their benefits and drawbacks, should be considered.

Activation of hypothalamic oxytocin neurons reduces binge-like alcohol drinking through signaling at central oxytocin receptors

Preclinical and clinical evidence suggests that exogenous administration of oxytocin (OT) may hold promise as a therapeutic strategy for reducing heavy alcohol drinking. However, it remains unknown whether these effects are mediated by stimulation of endogenous sources of OT and signaling at oxytocin receptors (OTR) in brain or in the periphery. To address this question, we employed a targeted chemogenetic approach to examine whether selective activation of OT-containing neurons in the paraventricular nucleus of the hypothalamus (PVN) alters alcohol consumption in a binge-like drinking ("Drinking-in-the-Dark"; DID) model. Adult male Oxt-IRES-Cre mice received bilateral infusion of a Cre-dependent virus containing an excitatory DREADD (AAV8-hSyn-DIO-hM3Dq-mCherry) or control virus (AAV8-hSyn-DIO-mCherry) into the PVN. Chemogenetic activation of PVNOT+ neurons following clozapine-N-oxide injection reduced binge-like alcohol drinking in a similar manner as systemic administration of the neuropeptide. Pretreatment with a brain-penetrant OTR antagonist (L-368,899) reversed this effect while systemic administration of a peripherally restricted OTR antagonist (Atosiban) did not alter reduced alcohol drinking following chemogenetic activation of PVNOT+ neurons. Altogether, these data are the first to demonstrate that targeted activation of hypothalamic (endogenous) OT reduces alcohol consumption, providing further evidence that this neuropeptide plays a role in regulation of alcohol self-administration behavior. Further, results indicate that the ability OT to reduce alcohol drinking is mediated by signaling at OTR in the brain.

Investigating hormone-induced changes in affective state using the affective bias test in male and female rats

Recent clinical and pre-clinical research suggests that affective biases may play an important role in the development and perpetuation of mood disorders. Studies in animals have also revealed that similar neuropsychological processes can be measured in non-human species using behavioural assays designed to measure biases in learning and memory or decision-making. Given the proposed links between hormones and mood, we used the affective bias test to investigate the effects of different hormone treatments in both male and female rats. Animals were pre-treated with acute doses of hormone or vehicle control prior to learning each of two independent substrate-reward associations. During a subsequent choice test, positive or negative biases were observed by animal's preference towards or away from the substrate learnt during drug treatment respectively. In both sexes, oestradiol and the oestrogen-like compound bisphenol A induced positive biases, whilst blockade of oestrogen hormones with formestane induced a negative bias. Progesterone induced a negative bias in both sexes, but testosterone only induced a negative bias in males. Blocking testosterone with flutamide induced a positive bias in both sexes at the higher dose (10 mg/kg). The oxytocin analogue, carbetocin induced positive biases in both sexes but the vasopressin analogue, desmopressin, induced a positive bias in male rats only. These results provide evidence that modulating levels of hormones using exogenous treatments can induce affective biases in rats. They also suggest that hormone-induced affective biases influence cognitive and emotional behaviour and could have longer-term effects in some mood disorders.

Oxytocin Ameliorates Impaired Behaviors of High Fat Diet-Induced Obese Mice

Excessive intake of fat is a major risk factor for lifestyle-related diseases such as heart disease and also affects brain function such as object recognition memory, social recognition, anxiety behavior, and depression-like behavior. Although oxytocin (OXT) has been reported to improve object recognition, social recognition, anxiety behavior, and depression-like behavior in specific conditions, previous studies did not explore the impact of OXT in high-fat diet (HFD)-fed mice. Furthermore, it remains unclear whether intake of HFD affects OXT/oxytocin receptor (OXTR) in the brain. Here, we demonstrated that peripheral OXT administration improves not only social recognition but also object recognition and depressive-like behavior in HFD-fed mice. In contrast, peripheral OXT administration to HFD-fed male mice increased fear and anxiety-related behavior. In addition, we observed that intake of HFD decreased OXTR and c-fos mRNA expression in the hippocampus, specifically. Furthermore, peripheral OXT administration increased OXT mRNA expression in the hypothalamus. Altogether, these findings suggest that OXT has the potential to improve various recognition memory processes via peripheral administration but also has side effects that increase fear-related behavior in males.

Oxytocin receptor agonist reduces perinatal brain damage by targeting microglia

Prematurity and fetal growth restriction (FGR) are frequent conditions associated with adverse neurocognitive outcomes. We have previously identified early deregulation of genes controlling neuroinflammation as a putative mechanism linking FGR and abnormal trajectory of the developing brain. While the oxytocin system was also found to be impaired following adverse perinatal events, its role in the modulation of neuroinflammation in the developing brain is still unknown. We used a double-hit rat model of perinatal brain injury induced by gestational low protein diet (LPD) and potentiated by postnatal injections of subliminal doses of interleukin-1β (IL1β) and a zebrafish model of neuroinflammation. Effects of the treatment with carbetocin, a selective, long lasting, and brain diffusible oxytocin receptor agonist, have been assessed using a combination of histological, molecular, and functional tools in vivo and in vitro. In the double-hit model, white matter inflammation, deficient myelination, and behavioral deficits have been observed and the oxytocin system was impaired. Early postnatal supplementation with carbetocin alleviated microglial activation at both transcriptional and cellular levels and provided long-term neuroprotection. The central anti-inflammatory effects of carbetocin have been shown in vivo in rat pups and in a zebrafish model of early-life neuroinflammation and reproduced in vitro on stimulated sorted primary microglial cell cultures from rats subjected to LPD. Carbetocin treatment was associated with beneficial effects on myelination, long-term intrinsic brain connectivity and behavior. Targeting oxytocin signaling in the developing brain may be an effective approach to prevent neuroinflammation - induced brain damage of perinatal origin.

Independent elevation of peripheral oxytocin concentrations and reduction in cognitive empathy during 4-fluoroamphetamine intoxication

OBJECTIVES

4-Fluoroamphetamine (4-FA) is a novel psychoactive substance with a pharmacological profile and reported subjective effects (e.g., empathy) intermediate between 3,4-methylenedioxymethamphetamine (MDMA) and amphetamine. Studies have shown that MDMA and amphetamine increase emotional empathy without affecting cognitive empathy; MDMA simultaneously leads to elevated levels of oxytocin, unrelated to its behavioral effects. The aim of the present study was to assess the reported enhancement of empathy by 4-FA, to assess its effects on oxytocin, and to test potential associations between both.

METHODS

Twelve healthy poly-drug users were included in a double-blind placebo-controlled two-way crossover study. Treatments were 4-FA (100 mg) and placebo; empathy was assessed by means of the multifaceted empathy test, and blood samples were taken before and after treatment administration to determine oxytocin concentrations.

RESULTS

4-FA reduced cognitive empathy, whereas emotional empathy was left unaffected. One hour after treatment, plasma oxytocin levels were significantly increased compared with placebo. Behavioral and hormonal effects were unrelated.

CONCLUSION

Although 4-FA shares its pharmacological mechanism with MDMA and amphetamine, current findings seem to indicate that it affects empathy differently. The 4-FA-induced increase in oxytocin levels was independent of behavioral effects, which confirms previous findings that drug-induced effects on peripheral oxytocin levels are not associated with empathy.

Oxytocin receptor gene variations and socio-emotional effects of MDMA: A pooled analysis of controlled studies in healthy subjects

Methylenedioxymethamphetamine (MDMA) increases oxytocin, empathy, and prosociality. Oxytocin plays a critical role in emotion processing and social behavior and has been shown to mediate the prosocial effects of MDMA in animals. Genetic variants, such as single-nucleotide polymorphisms (SNPs), of the oxytocin receptor (OXTR) may influence the emotional and social effects of MDMA in humans. The effects of common genetic variants of the OXTR (rs53576, rs1042778, and rs2254298 SNPs) on the emotional, empathogenic, and prosocial effects of MDMA were characterized in up to 132 healthy subjects in a pooled analysis of eight double-blind, placebo-controlled studies. In a subset of 53 subjects, MDMA produced significantly greater feelings of trust in rs1042778 TT genotypes compared with G allele carriers. The rs53576 and rs225498 SNPs did not moderate the subjective effects of MDMA in up to 132 subjects. None of the SNPs moderated MDMA-induced impairments in negative facial emotion recognition or enhancements in emotional empathy in the Multifaceted Empathy Test in 69 subjects. MDMA significantly increased plasma oxytocin concentrations. MDMA and oxytocin concentrations did not differ between OXTR gene variants. The present results provide preliminary evidence that OXTR gene variations may modulate aspects of the prosocial subjective effects of MDMA in humans. However, interpretation should be cautious due to the small sample size. Additionally, OXTR SNPs did not moderate the subjective overall effect of MDMA (any drug effect) or feelings of “closeness to others”.

Trial registration: ClinicalTrials.gov: http://www.clinicaltrials.gov, No: NCT00886886, NCT00990067, NCT01136278, NCT01270672, NCT01386177, NCT01465685, NCT01771874, and NCT01951508.

Oxytocin, Tolerance, and the Dark Side of Addiction

Substance use disorders blight the lives of millions of people and inflict a heavy financial burden on society. There is a compelling need for new pharmacological treatments as current drugs have limited efficacy and other major drawbacks. A substantial number of animal and recent clinical studies indicate that the neuropeptide, oxytocin, is a particularly promising therapeutic agent for human addictions, especially alcohol use disorders. In preliminary trials, we found that oxytocin administered by the intranasal route, which produces some neuropeptide penetration into the CNS, potently blocked withdrawal and reduced alcohol consumption in heavy drinkers. A considerable body of earlier animal studies demonstrated that oxytocin inhibits tolerance to alcohol, opioids, and stimulants as well as withdrawal from alcohol and opioids. Based on these preclinical findings and our clinical results, we hypothesize that oxytocin may exert therapeutic effects in substance dependence by the novel mechanism of diminishing established tolerance. A newer wave of studies has almost unanimously found that oxytocin decreases self-administration of a number of addictive substances in several animal models of addiction. Reduction of established tolerance should be included among the potential explanations of oxytocin effects in these studies and changes in tolerance should be examined in future studies in relationship to oxytocin influences on acquisition and reinstatement of self-administration as well as extinction of drug seeking. Oxytocin efficacy in reducing anxiety and stress responses as well as established tolerance suggests it may be uniquely effective in reducing negative reinforcement (Koob's "dark side" of addiction) that maintains chronic substance use.

Recreational 3,4-methylenedioxymethamphetamine or 'ecstasy': Current perspective and future research prospects

AIMS

The purpose of this article is to debate current understandings about the psychobiological effects of recreational 3,4-methylenedioxymethamphetamine (MDMA or 'ecstasy'), and recommend theoretically-driven topics for future research.

METHODS

Recent empirical findings, especially those from novel topic areas were reviewed. Potential causes for the high variance often found in group findings were also examined.

RESULTS AND CONCLUSIONS

The first empirical reports into psychobiological and psychiatric aspects from the early 1990s concluded that regular users demonstrated some selective psychobiological deficits, for instance worse declarative memory, or heightened depression. More recent research has covered a far wider range of psychobiological functions, and deficits have emerged in aspects of vision, higher cognitive skill, neurohormonal functioning, and foetal developmental outcomes. However, variance levels are often high, indicating that while some recreational users develop problems, others are less affected. Potential reasons for this high variance are debated. An explanatory model based on multi-factorial causation is then proposed.

FUTURE DIRECTIONS

A number of theoretically driven research topics are suggested, in order to empirically investigate the potential causes for these diverse psychobiological deficits. Future neuroimaging studies should study the practical implications of any serotonergic and/or neurohormonal changes, using a wide range of functional measures.

Oxytocin Pathway Genes: Evolutionary Ancient System Impacting on Human Affiliation, Sociality, and Psychopathology

Oxytocin (OT), a nonapeptide signaling molecule originating from an ancestral peptide, appears in different variants across all vertebrate and several invertebrate species. Throughout animal evolution, neuropeptidergic signaling has been adapted by organisms for regulating response to rapidly changing environments. The family of OT-like molecules affects both peripheral tissues implicated in reproduction, homeostasis, and energy balance, as well as neuromodulation of social behavior, stress regulation, and associative learning in species ranging from nematodes to humans. After describing the OT-signaling pathway, we review research on the three genes most extensively studied in humans: the OT receptor (OXTR), the structural gene for OT (OXT/neurophysin-I), and CD38. Consistent with the notion that sociality should be studied from the perspective of social life at the species level, we address human social functions in relation to OT-pathway genes, including parenting, empathy, and using social relationships to manage stress. We then describe associations between OT-pathway genes with psychopathologies involving social dysfunctions such as autism, depression, or schizophrenia. Human research particularly underscored the involvement of two OXTR single nucleotide polymorphisms (rs53576, rs2254298) with fewer studies focusing on other OXTR (rs7632287, rs1042778, rs2268494, rs2268490), OXT (rs2740210, rs4813627, rs4813625), and CD38 (rs3796863, rs6449197) single nucleotide polymorphisms. Overall, studies provide evidence for the involvement of OT-pathway genes in human social functions but also suggest that factors such as gender, culture, and early environment often confound attempts to replicate first findings. We conclude by discussing epigenetics, conceptual implications within an evolutionary perspective, and future directions, especially the need to refine phenotypes, carefully characterize early environments, and integrate observations of social behavior across ecological contexts.

Postpartum depression: Etiology, treatment and consequences for maternal care

This article is part of a Special Issue "Parental Care". Pregnancy and postpartum are associated with dramatic alterations in steroid and peptide hormones which alter the mothers' hypothalamic pituitary adrenal (HPA) and hypothalamic pituitary gonadal (HPG) axes. Dysregulations in these endocrine axes are related to mood disorders and as such it should not come as a major surprise that pregnancy and the postpartum period can have profound effects on maternal mood. Indeed, pregnancy and postpartum are associated with an increased risk for developing depressive symptoms in women. Postpartum depression affects approximately 10-15% of women and impairs mother-infant interactions that in turn are important for child development. Maternal attachment, sensitivity and parenting style are essential for a healthy maturation of an infant's social, cognitive and behavioral skills and depressed mothers often display less attachment, sensitivity and more harsh or disrupted parenting behaviors, which may contribute to reports of adverse child outcomes in children of depressed mothers. Here we review, in honor of the "father of motherhood", Jay Rosenblatt, the literature on postnatal depression in the mother and its effect on mother-infant interactions. We will cover clinical and pre-clinical findings highlighting putative neurobiological mechanisms underlying postpartum depression and how they relate to maternal behaviors and infant outcome. We also review animal models that investigate the neurobiology of maternal mood and disrupted maternal care. In particular, we discuss the implications of endogenous and exogenous manipulations of glucocorticoids on maternal care and mood. Lastly we discuss interventions during gestation and postpartum that may improve maternal symptoms and behavior and thus may alter developmental outcome of the offspring.

Recreational 3,4-methylenedioxy-N-methylamphetamine (MDMA) or 'ecstasy' and self-focused compassion: Preliminary steps in the development of a therapeutic psychopharmacology of contemplative practices

3,4-methylenedioxy-N-methylamphetamine (MDMA) produces diverse pro-social effects. Cognitive training methods rooted in Eastern contemplative practices also produce these effects through the development of a compassionate mindset. Given this similarity, we propose that one potential mechanism of action of MDMA in psychotherapy is through enhancing effects on intrapersonal attitudes (i.e. pro-social attitudes towards the self). We provide a preliminary test of this idea. Recreational MDMA (ecstasy) users were tested on two occasions, having consumed or not consumed ecstasy. Self-critical and self-compassionate responses to self-threatening scenarios were assessed before (T1) and after (T2) ecstasy use (or non-use), and then after compassionate imagery (T3). Moderating roles of dispositional self-criticism and avoidant attachment were examined. Separately, compassionate imagery and ecstasy produced similar sociotropic effects, as well as increases in self-compassion and reductions in self-criticism. Higher attachment-related avoidance was associated with additive effects of compassionate imagery and ecstasy on self-compassion. Findings were in line with MDMA's neuropharmacological profile, its phenomenological effects and its proposed adjunctive use in psychotherapy. However, although conditions were balanced, the experiment was non-blind and MDMA dose/purity was not determined. Controlled studies with pharmaceutically pure MDMA are still needed to test these effects rigorously.

Effects of atosiban on stress-related neuroendocrine factors

Atosiban, an oxytocin/vasopressin receptor antagonist, is used to decrease preterm uterine activity. The risk of preterm delivery is undoubtedly associated with stress, but potential side effects of atosiban on neuroendocrine functions and stress-related pathways are mostly unknown. These studies were designed to test the hypothesis that the chronic treatment of rats with atosiban modulates neuroendocrine functions under stress conditions. Male rats were treated (osmotic minipumps) with atosiban (600 μg/kg per day) or vehicle and were restrained for 120 min/day for 14 days. All animals were treated with a marker of cell proliferation 5-bromo-2-deoxyuridine. Anxiety-like behavior was measured using an elevated plus-maze. Treatment with atosiban failed to modify plasma concentrations of the stress hormones ACTH and corticosterone, but led to a rise in circulating copeptin. Atosiban increased prolactin levels in the non-stressed group. Oxytocin receptor mRNA levels were increased in rats exposed to stress. Treatment with atosiban, in both control and stressed animals, resulted in a decrease in oxytocin receptor gene expression in the hypothalamus. No changes were observed in vasopressin receptor 1A and 1B gene expression. The decrease in hippocampal cell proliferation induced by stress exposure was not modified by atosiban treatment. This study provides the first data, to our knowledge, revealing the effect of atosiban on gene expression of oxytocin receptors in the brain. Atosiban-induced enhancement of plasma copeptin indicates an elevation in vasopressinergic tone with potential influence on water-electrolyte balance.

Oxytocin treatment in pediatric populations

The role of endogenous oxytocin as neuromodulator of birth, lactation and social behaviors is well-recognized. Moreover, the use of oxytocin as a facilitator of social and other behaviors is becoming more and more accepted. Many positive effects have been attributed to intranasal oxytocin administration in animals and humans; with current research highlighting encouraging advances in its potential for use in mental health disorders. The new frontier will be investigating the effective use of oxytocin in pediatric populations. Limited animal data is available on this. Large-scale human studies focusing on autism are currently under way, but many other possibilities seem to lie in the future. However, we need to know more about the risks and effects of repeated use on the developing brain and body. This paper will provide an overview of the current understanding of the role of endogenous oxytocin and its related neuropeptide systems in influencing behaviors, in particular attachment, and will review (a) the literature on the use of intranasal oxytocin in young animals, children (age range birth-12 years) and adolescents (age range 13-19 years), (b) the expected benefits and risks based on the current research, and (c) the risks of oxytocin in children with severe psychopathology and early life trauma. The paper will conclude with a clinical perspective on these findings.

Role of neuropeptides in anxiety, stress, and depression: from animals to humans

Major depression, with its strikingly high prevalence, is the most common cause of disability in communities of Western type, according to data of the World Health Organization. Stress-related mood disorders, besides their deleterious effects on the patient itself, also challenge the healthcare systems with their great social and economic impact. Our knowledge on the neurobiology of these conditions is less than sufficient as exemplified by the high proportion of patients who do not respond to currently available medications targeting monoaminergic systems. The search for new therapeutical strategies became therefore a "hot topic" in neuroscience, and there is a large body of evidence suggesting that brain neuropeptides not only participate is stress physiology, but they may also have clinical relevance. Based on data obtained in animal studies, neuropeptides and their receptors might be targeted by new candidate neuropharmacons with the hope that they will become important and effective tools in the management of stress related mood disorders. In this review, we attempt to summarize the latest evidence obtained using animal models for mood disorders, genetically modified rodent models for anxiety and depression, and we will pay some attention to previously published clinical data on corticotropin releasing factor, urocortin 1, urocortin 2, urocortin 3, arginine-vasopressin, neuropeptide Y, pituitary adenylate-cyclase activating polypeptide, neuropeptide S, oxytocin, substance P and galanin fields of stress research.