Brain oxytocin inhibits basal and stress-induced activity of the hypothalamo-pituitary-adrenal axis in male and female rats: partial action within the paraventricular nucleus

The Oxytocin Receptor: From Intracellular Signaling to Behavior

The many facets of the oxytocin (OXT) system of the brain and periphery elicited nearly 25,000 publications since 1930 (see FIGURE 1 , as listed in PubMed), which revealed central roles for OXT and its receptor (OXTR) in reproduction, and social and emotional behaviors in animal and human studies focusing on mental and physical health and disease. In this review, we discuss the mechanisms of OXT expression and release, expression and binding of the OXTR in brain and periphery, OXTR-coupled signaling cascades, and their involvement in behavioral outcomes to assemble a comprehensive picture of the central and peripheral OXT system. Traditionally known for its role in milk let-down and uterine contraction during labor, OXT also has implications in physiological, and also behavioral, aspects of reproduction, such as sexual and maternal behaviors and pair bonding, but also anxiety, trust, sociability, food intake, or even drug abuse. The many facets of OXT are, on a molecular basis, brought about by a single receptor. The OXTR, a 7-transmembrane G protein-coupled receptor capable of binding to either Gαior Gαqproteins, activates a set of signaling cascades, such as the MAPK, PKC, PLC, or CaMK pathways, which converge on transcription factors like CREB or MEF-2. The cellular response to OXT includes regulation of neurite outgrowth, cellular viability, and increased survival. OXTergic projections in the brain represent anxiety and stress-regulating circuits connecting the paraventricular nucleus of the hypothalamus, amygdala, bed nucleus of the stria terminalis, or the medial prefrontal cortex. Which OXT-induced patterns finally alter the behavior of an animal or a human being is still poorly understood, and studying those OXTR-coupled signaling cascades is one initial step toward a better understanding of the molecular background of those behavioral effects.

Prenatal stress disrupts social behavior, cortical neurobiology and commensal microbes in adult male offspring

In utero and early neonatal exposure to maternal stress is linked with psychiatric disorders, and the underlying mechanisms are currently being elucidated. We used a prenatal stressor in pregnant mice to examine novel relationships between prenatal stress exposure, changes in the gut microbiome, and social behavior. Here, we show that males exposed to prenatal stress had a significant reduction in social behavior in adulthood, with increased corticosterone release following social interaction. Male offspring exposed to prenatal stress also had neuroinflammation, decreased oxytocin receptor, and decreased serotonin metabolism in their cortex in adulthood, which are linked to decreased social behavior. Finally, we found a significant difference in commensal microbes, including decreases in Bacteroides and Parabacteroides, in adult male offspring exposed to prenatal stress when compared to non-stressed controls. Our findings indicate that gestation is a critical window where maternal stress contributes to the development of aberrant social behaviors and alterations in cortical neurobiology, and that prenatal stress is sufficient to disrupt the male gut-brain axis into adulthood.

The interplay between oxytocin and the CRF system: regulation of the stress response

Oxytocin (OT) has drawn the attention of researchers since 1930. Since then, many aspects of oxytocin have been uncovered, such as reproductive functions, dampening anxiety, enhancing socioemotional behavior, or regulating genomic effects on a cellular level. Here, we want to focus on the interaction between the OT system and the stress/corticotropin-releasing factor (CRF)-system of the brain. Depending on the nature of the stressor, OT is released simultaneously or directly after the stress from the neurohypophysis into the periphery and/or via somato-dendritic release in stress-sensitive brain areas. This stress-induced OT release might serve to modulate or dampen the stress response; however, the functional relevance is not yet fully understood. In this review, we will describe the effects of OT and discuss the interplay between OT and CRF on a cellular, physiological, and behavioral level.

Medications for alcohol use disorders: An overview

Patients who suffer from alcohol use disorders (AUDs) usually go through various socio-behavioral and pathophysiological changes that take place in the brain and other organs. Recently, consumption of unhealthy food and excess alcohol along with a sedentary lifestyle has become a norm in both developed and developing countries. Despite the beneficial effects of moderate alcohol consumption, chronic and/or excessive alcohol intake is reported to negatively affect the brain, liver and other organs, resulting in cell death, organ damage/failure and death. The most effective therapy for alcoholism and alcohol related comorbidities is alcohol abstinence, however, chronic alcoholic patients cannot stop drinking alcohol. Therefore, targeted therapies are urgently needed to treat such populations. Patients who suffer from alcoholism and/or alcohol abuse experience harmful effects and changes that occur in the brain and other organs. Upon stopping alcohol consumption, alcoholic patients experience acute withdrawal symptoms followed by a protracted abstinence syndrome resulting in the risk of relapse to heavy drinking. For the past few decades, several drugs have been available for the treatment of AUDs. These drugs include medications to reduce or stop severe alcohol withdrawal symptoms during alcohol detoxification as well as recovery medications to reduce alcohol craving and support abstinence. However, there is no drug that completely antagonizes the adverse effects of excessive amounts of alcohol. This review summarizes the drugs which are available and approved by the FDA and their mechanisms of action as well as the medications that are under various phases of preclinical and clinical trials. In addition, the repurposing of the FDA approved drugs, such as anticonvulsants, antipsychotics, antidepressants and other medications, to prevent alcoholism and treat AUDs and their potential target mechanisms are summarized.

Modulating the Oxytocin System During the Perinatal Period: A New Strategy for Neuroprotection of the Immature Brain?

Oxytocin is a neurohypophysal hormone known for its activity during labor and its role in lactation. However, the function of oxytocin (OTX) goes far beyond the peripheral regulation of reproduction, and the central effects of OTX have been extensively investigated, since it has been recognized to influence the learning and memory processes. OTX has also prominent effects on social behavior, anxiety, and autism. Interaction between glucocorticoids, OTX, and maternal behavior may have long-term effects on the developmental program of the developing brain subjected to adverse events during pre and perinatal periods. OTX treatment in humans improves many aspects of social cognition and behavior. Its effects on the hypothalamic–pituitary–adrenal axis and inflammation appear to be of interest in neonates because these properties may confer benefits when the perinatal brain has been subjected to injury. Indeed, early life inflammation and abnormal adrenal response to stress have been associated with an abnormal white matter development. Recent investigations demonstrated that OTX is involved in the modulation of microglial reactivity in the developing brain. This review recapitulates state-of-the art data supporting the hypothesis that the OTX system could be considered as an innovative candidate for neuroprotection, especially in the immature brain.

Inhibitory effect of the Kampo medicinal formula Yokukansan on acute stress-induced defecation in rats

OBJECTIVES

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder with symptoms of abnormal defecation and abdominal discomfort. Psychological factors are well known to be involved in onset and exacerbation of IBS. A few studies have reported effectiveness of traditional herbal (Kampo) medicines in IBS treatment. Yokukansan (YKS) has been shown to have anti-stress and anxiolytic effects. We investigated the effect of YKS on defecation induced by stress and involvement of oxytocin (OT), a peptide hormone produced by the hypothalamus, in order to elucidate the mechanism of YKS action.

METHODS AND RESULTS

Male Wistar rats were divided into four groups; control, YKS (300 mg/kg PO)-treated non-stress (YKS), acute stress (Stress), and YKS (300 mg/kg PO)-treated acute stress (Stress+YKS) groups. Rats in the Stress and Stress+YKS groups were exposed to a 15-min psychological stress procedure involving novel environmental stress. Levels of plasma OT in the YKS group were significantly higher compared with those in the Control group (P < 0.05), and OT levels in the Stress+YKS group were remarkably higher than those in the other groups (P < 0.01). Next, rats were divided into four groups; Stress, Stress+YKS, Atosiban (OT receptor antagonist; 1 mg/kg IP)-treated Stress+YKS (Stress+YKS+B), and OT (0.04 mg/kg IP)-treated acute stress (Stress+OT) groups. Rats were exposed to acute stress as in the previous experiment, and defecation during the stress load was measured. Administration of YKS or OT significantly inhibited defecation; however, administration of Atosiban partially abolished the inhibitory effect of YKS. Finally, direct action of YKS on motility of isolated colon was assessed. YKS (1 mg/mL, 5 mg/mL) did not inhibit spontaneous contraction.

CONCLUSION

These results suggested that YKS influences stress-induced defecation and that increased OT secretion may be a mechanism underlying this phenomenon.

Rapid nonapeptide synthesis during a critical period of development in the prairie vole: plasticity of the paraventricular nucleus of the hypothalamus

Vasopressin (VP) and oxytocin (OT) are involved in modulating basic physiology and numerous social behaviors. Although the anatomical distributions of nonapeptide neurons throughout development have been described, the functional roles of VP and OT neurons during development are surprisingly understudied, and it is unknown whether they exhibit functional changes throughout early development. We utilized an acute social isolation paradigm to determine if VP and OT neural responses in eight nonapeptide cell groups differ at three different stages of early development in prairie voles. We tested pups at ages that are representative of the three rapid growth stages of the developing brain: postnatal day (PND)2 (closed eyes; poor locomotion), PND9 (eye opening; locomotion; peak brain growth spurt), and PND21 (weaning). Neural responses were examined in pups that (1) were under normal family conditions with their parents and siblings, (2) were isolated from their parents and siblings and then reunited, and (3) were isolated from their parents and siblings. We found that VP and OT neural activity (as assessed via Fos co-localization) did not differ in response to social condition across development. However, remarkably rapid VP and OT synthesis in response to social isolation was observed only in the paraventricular nucleus of the hypothalamus (PVN) and only in PND9 pups. These results suggest that PVN nonapeptide neurons exhibit distinct cellular properties during a critical period of development, allowing nonapeptide neurons to rapidly upregulate peptide production in response to stressors on a much shorter timescale than has been observed in adult animals.

Beneficial effects of chronic oxytocin administration and social co-housing in a rodent model of post-traumatic stress disorder

Post-traumatic stress disorder (PTSD) is in part due to a deficit in memory consolidation and extinction. Oxytocin (OXT) has anxiolytic effects and promotes prosocial behaviors in both rodents and humans, and evidence suggests that it plays a role in memory consolidation. We studied the effects of administered OXT and social co-housing in a rodent model of PTSD. Acute OXT yielded a short-term increase in the recall of the traumatic memory if administered immediately after trauma. Low doses of OXT delivered chronically had a cumulating anxiolytic effect that became apparent after 4 days and persisted. Repeated injections of OXT after short re-exposures to the trauma apparatus yielded a long-term reduction in anxiety. Co-housing with naive nonshocked animals decreased the memory of the traumatic context compared with single-housed animals. In the long term, these animals showed less thigmotaxis and increased interest in novel objects, and a low OXT plasma level. Co-housed PTSD animals showed an increase in risk-taking behavior. These results suggest beneficial effects of OXT if administered chronically through increases in memory consolidation after re-exposure to a safe trauma context. We also show differences between the benefits of social co-housing with naive rats and co-housing with other shocked animals on trauma-induced long-term anxiety.

Effects of nucleus accumbens oxytocin and its antagonist on social approach behavior

Severe impairment of social interaction is a core symptom of numerous psychiatric disorders. Oxytocin (OT) has been shown to be involved in various aspects of social behavior related to reproduction, but little is known about its effects on nonreproductive social interaction between adults or the neuroanatomical location where OT exerts its action. Here, we examined the nucleus accumbens, a region of the brain containing high levels of the oxytocin receptor (OTR) and comprising an important node in the neural circuitry possibly related to social interaction. Behavioral effects of a local microinfusion of OT (0.1, 1, and 10 ng/side) and an oxytocin receptor antagonist (OTR-A) (1, 10, and 100 ng/side) were evaluated in naturally high social and low social female and male monogamous mandarin voles (Microtus mandarinus) using the social preference paradigm and open-field tests. The results showed that administration of 1 ng/side OT increased social preference; however, this effect was not apparent at lower or higher doses. OT did not alter anxiety-like behavior or total locomotion. Microinfusions of a selective OTR-A at 10 and 100 ng doses reduced social approach behavior; a dose of 1 ng had no effect. In conclusion, our results suggest that accumbal OT and OTR-A regulate social preferences in voles in a dose-dependent manner.

Paternal Care Impacts Oxytocin Expression in California Mouse Offspring and Basal Testosterone in Female, but Not Male Pups

Natural variations in parenting are associated with differences in expression of several hormones and neuropeptides which may mediate lasting effects on offspring development, like regulation of stress reactivity and social behavior. Using the bi-parental California mouse, we have demonstrated that parenting and aggression are programmed, at least in part, by paternal behavior as adult offspring model the degree of parental behavior received in development and are more territorial following high as compared to low levels of care. Development of these behaviors may be driven by transient increases in testosterone following paternal retrievals and increased adult arginine vasopressin (AVP) immunoreactivity within the bed nucleus of the stria terminalis (BNST) among high-care (HC) offspring. It remains unclear, however, whether other neuropeptides, such as oxytocin (OT), which is sensitive to gonadal steroids, are similarly impacted by father-offspring interactions. To test this question, we manipulated paternal care (high and low care) and examined differences in adult offspring OT-immunoreactive (OT-ir) within social brain areas as well as basal T and corticosterone (Cort) levels. HC offspring had more OT-ir within the paraventricular nucleus (PVN) and supraoptic nucleus (SON) than low-care (LC) offspring. Additionally, T levels were higher among HC than LC females, but no differences were found in males. There were no differences in Cort indicating that our brief father-pup separations likely had no consequences on stress reactivity. Together with our previous work, our data suggest that social behavior may be programmed by paternal care through lasting influences on the neuroendocrine system.

Postpartum Lactation-Mediated Behavioral Outcomes and Drug Responses in a Spontaneous Mouse Model of Obsessive-Compulsive Disorder

Using a spontaneous mouse model of obsessive-compulsive disorder (OCD), the current study evaluated the influence of postpartum lactation on the expression of compulsive-like behaviors, SSRI effectiveness, and the putative role of oxytocin and dopamine in mediating these lactation specific behavioral outcomes. Compulsive-like lactating mice were less compulsive-like in nest building and marble burying and showed enhanced responsiveness to fluoxetine (50 mg/kg) in comparison to compulsive-like nonlactating and nulliparous females. Lactating mice exhibited more anxiety-like behavior in the open field test compared to the nulliparous females, while chronic fluoxetine reduced anxiety-like behaviors. Blocking the oxytocin receptor with L368-899 (5 mg/kg) in the lactating mice exacerbated the compulsive-like and depression-like behaviors. The dopamine D2 receptor (D2R) agonist bromocriptine (10 mg/kg) suppressed marble burying, nest building, and central entries in the open field, but because it also suppressed overall locomotion in the open field, activation of the D2R receptor may have inhibited overall activity nonspecifically. Lactation- and fluoxetine-mediated behavioral outcomes in compulsive-like mice, therefore, appear to be partly regulated by oxytocinergic mechanisms. Serotonin immunoreactivity and serum levels were higher in lactating compulsive-like mice compared to nonlactating and nulliparous compulsive-like females. Together, these results suggest behavioral modulation, serotonergic alterations, and changes in SSRI effectiveness during lactation in compulsive-like mice. This warrants further investigation of postpartum events in OCD patients.

Increased exposure to sodium during pregnancy and lactation changes basal and induced behavioral and neuroendocrine responses in adult male offspring

Excessive sodium (Na⁺) intake in modern society has been associated with several chronic disorders such as hypertension. Several studies suggest that early life events can program physiological systems and lead to functional changes in adulthood. Therefore, we investigated behavioral and neuroendocrine responses under basal conditions and after 48 h of water deprivation in adult (60‐day‐old Wistar rats) male, Wistar rats originating from dams were offered only water or 0.15 mol/L NaCl during pregnancy and lactation. Early life salt exposure induced kidney damage, as shown by a higher number of ED‐1 positive cells (macrophages/monocytes), increased daily urinary volume and Na⁺ excretion, blunted basal water intake and plasma oxytocin levels, and increased plasma corticosterone secretion. When challenged with water deprivation, animals exposed to 0.15 mol/L NaCl during early life showed impaired water intake, reduced salt preference ratio, and vasopressin (AVP) secretion. In summary, our data demonstrate that the perinatal exposure to excessive Na⁺ intake can induce kidney injury in adult offspring and significantly affect the key mechanisms regulating water balance, fluid intake, and AVP release in response to water deprivation. Collectively, these novel results highlight the impact of perinatal programming on the homeostatic mechanisms regulating fluid and electrolyte balance during exposure to an environmental stress (i.e. dehydration) in later life.

Rebalancing the Addicted Brain: Oxytocin Interference with the Neural Substrates of Addiction

Drugs that act on the brain oxytocin (OXT) system may provide a much-needed treatment breakthrough for substance-use disorders. Targeting the brain OXT system has the potential to treat addiction to all major classes of addictive substance and to intervene across all stages of the addiction cycle. Emerging evidence suggests that OXT is able to interfere with such a wide range of addictive behaviours for such a wide range of addictive substances by rebalancing core neural systems that become dysregulated over the course of addiction. By improving our understanding of these interactions between OXT and the neural substrates of addiction, we will not only improve our understanding of addiction, but also our ability to effectively treat these devastating disorders.

Regulation of hypothalamic corticotropin-releasing hormone neurone excitability by oxytocin

Oxytocin (OT) is a neuropeptide that exerts multiple actions throughout the brain and periphery. Within the brain, OT regulates diverse neural populations, including neural networks controlling responses to stress. Local release of OT within the paraventricular nucleus (PVN) of the hypothalamus has been suggested to regulate stress responses by modulating the excitability of neighbouring corticotropin-releasing hormone (CRH) neurones. However, the mechanisms by which OT regulates CRH neurone excitability are unclear. In the present study, we investigated the morphological relationship between OT and CRH neurones and determined the effects of OT on CRH neurone excitability. Morphological analysis revealed that the processes of OT and CRH neurones were highly intermingled within the PVN, possibly allowing for local cell-to-cell cross-talk. Whole-cell patch-clamp recordings from CRH neurones were used to study the impact of OT on postsynaptic excitability and synaptic innervation. Bath-applied OT did not alter CRH neurone holding current, spiking output or any action potential parameters. Recordings of evoked excitatory and inhibitory postsynaptic currents (EPSCs/IPSCs) revealed no net effect of OT on current amplitude; however, subgroups of CRH neurones appeared to respond differentially to OT. Analysis of spontaneous EPSC events uncovered a significant reduction in spontaneous EPSC frequency but no change in spontaneous EPSC amplitude in response to OT. Together, these data demonstrate that OT exerts a subtle modulation of synaptic transmission onto CRH neurones providing one potential mechanism by which OT could suppress CRH neurone excitability and stress axis activity.

Emotional maltreatment is associated with atypical responding to stimulation of endogenous oxytocin release through mechanically-delivered massage in males

The neuropeptide oxytocin plays an important role in social behavior, parenting, and affectionate touch and there is some evidence that oxytocin release can be stimulated by massage or affectionate touch. We examined the effects of massage applied by a massage seat cover on salivary oxytocin levels in two exploratory studies using within-subject designs. In Study 1 massage effects on oxytocin levels were examined in a sample of N=20 healthy female participants. Effects of a 15-min massage session were compared to a control condition during which participants sat on a comfortable chair without a massage seat cover. Salivary oxytocin levels were measured at baseline and up to three hours after the session. We found that massage attenuated oxytocin decreases over time, indicating that massage stimulates oxytocin release. In Study 2, we examined whether effects of massage in N=46 healthy male participants depend on experiences of emotional maltreatment. In addition, we examined whether enhanced oxytocin levels after massage affect the use of excessive handgrip force in response to infant crying and laughter as measured with a handgrip dynamometer. Our findings show that massage results in elevated oxytocin levels compared to a control condition, but that the effects of massage are dependent on experiences of emotional maltreatment. Men with experiences of emotional maltreatment showed lower oxytocin levels, which did not increase after massage. Furthermore, we found that high oxytocin levels after massage were related to reduced handgrip force during exposure to infant crying and laughter, indicating that massage stimulates a sensitive response to infant signals by stimulating oxytocin release. Although massage did not affect oxytocin levels in individuals with experiences of maltreatment, it reduced the use of handgrip force in response to infant crying and laughter in these individuals. Our findings indicate that emotional maltreatment is associated with atypical responding to stimulation of endogenous oxytocin release.

Increased Serum and Urinary Oxytocin Concentrations after Nasal Administration in Beagle Dogs

In recent years more and more studies have revealed the effect of extraneous oxytocin on the social behavior of dogs. The distribution of administered oxytocin in different physiologically relevant compartments is important because this knowledge forms the basis for the timing of behavior tests after the administration. Most behavioral studies rely on the non-invasive intranasal application of oxytocin. The aim of this study was to determine the time course of intranasal administered oxytocin secretion into blood and urine and also establish a connection between intranasal received oxytocin and urinary cortisol in dogs. In our experiment, four dogs received three puffs, 12 IU intranasal oxytocin treatment, two dogs received three puffs intranasal placebo treatment. Blood and urine samples were collected immediately prior to the administration then regularly during 4 h. After nasal oxytocin application, the serum oxytocin concentration increased, reached a maximum 15 min after the treatment and then rapidly returned to baseline levels 45 min later. The peak urinary oxytocin concentration occurred between 45 and 60 min after administration and returned to baseline levels slowly. We found considerable differences among individuals in the secretion of oxytocin in both the serum and the urinary oxytocin concentration measurements. Our results confirm that intranasally administered oxytocin passes into the blood stream. The time course of intranasally administered oxytocin secretion is similar to the time course of intravenously administered oxytocin secretion, and the peak values are also similar in both the serum and the urinary oxytocin concentration measurements, although there are large individual differences.

The role of prolactin in the suppression of Crh mRNA expression during pregnancy and lactation in the mouse

Maternal stress is associated with negative health consequences for both the mother and her offspring. To prevent these adverse outcomes, activity of the hypothalamic-pituitary-adrenal (HPA) axis is attenuated during pregnancy and lactation. Although the mechanisms generating this adaptive change have not been defined fully, the anterior pituitary hormone prolactin may play a significant role. The present study investigated the role of prolactin in regulating the basal activity of the HPA axis during pregnancy and lactation in the mouse, focussing upon the corticotrophin-releasing hormone (CRH) neurones. Using in situ hybridisation, a decrease in Crh mRNA-expressing cell number in pregnant (55.6±9.0 cells per section) and lactating (97.4±4.9) mice compared to virgin controls was characterised (186.8±18.7, P<.01 Tukey-Kramer test; n=6-7 per group). Removal of the pups (24 hours) and thus the associated suckling-induced prolactin secretion, restored CRH neurone number (180.1±19.7). To specifically test the role of prolactin in suppressing Crh mRNA expression in lactation, prolactin levels were selectively manipulated in lactating mice. Lactating mice were treated with ovine prolactin (1500 μg day^-1 , osmotic minipump, s.c.; n=7) or vehicle (n=6) for 24 hours following pup removal. This was sufficient to suppress Crh mRNA expression from 108.0±13.5 to 53.7±16.7 cells per section (P<.05 Student's t-test). Additional cohorts of lactating mice were treated with bromocriptine (300 μg over 24 hours, s.c.; n=7) or vehicle (n=5) to suppress endogenous prolactin secretion; however, no change in Crh mRNA expression was detected. Thus, although prolactin was sufficient to suppress Crh mRNA expression in the paraventricular nucleus, it does not appear to be required for the ongoing regulation of the CRH neurones in lactation.

Distribution and chemical composition of estrogen receptor β neurons in the paraventricular nucleus of the female and male mouse hypothalamus

Activation of estrogen receptor beta (ERβ)-expressing neurons regulates the mammalian stress response via the hypothalamic-pituitary-adrenal (HPA) axis. These neurons densely populate the paraventricular nucleus of the hypothalamus (PVN). Recent research has revealed striking differences between rat and mouse PVN cytochemistry, but careful exploration of PVN ERβ neurons in mice has been hindered by a lack of specific ERβ antisera. Therefore, we used male and female transgenic mice expressing EGFP under the control of the mouse ERβ promoter (ERβ-EGFP) to examine the chemical architecture of PVN ERβ cells. Using immunohistochemistry, we found that 90% of ERβ-immunoreactivity (-ir) colocalized with EGFP. Cellular colocalization of EGFP with neuropeptides, transcription modulators, and neuronal tracers was examined throughout the PVN. ERβ-EGFP cells expressed oxytocin more abundantly in the rostral (71 ± 3%) than caudal (33 ± 8%) PVN. Arginine vasopressin colocalized with EGFP more often in females (18 ± 3%) than males (4 ± 1%). Moreover, estrogen receptor α-ir colocalized with ERβ-EGFP at low levels (15 ± 3%). Using a corticotropin releasing hormone-cre driver X tdTomato reporter mouse, we found a moderate colocalization with ERβ-ir (48 ± 16%) in the middle PVN. Peripheral injection of fluorogold revealed that the rostral PVN ERβ-EGFP cells are neuroendocrine neurons whereas non-neuroendocrine (presumably pre-autonomic) ERβ-EGFP neurons predominated in the posterior PVN. These data demonstrate chemoarchitectural differences in ERβ neurons of the mouse PVN that are different from that previously described for the rat, thus, elucidating potential neuronal pathways involved in the regulation of the HPA axis in mice.

Influence of stress associated with chronic alcohol exposure on drinking

Stress is commonly regarded as an important trigger for relapse and a significant factor that promotes increased motivation to drink in some individuals. However, the relationship between stress and alcohol is complex, likely changing in form during the transition from early moderated alcohol use to more heavy uncontrolled alcohol intake. A growing body of evidence indicates that prolonged excessive alcohol consumption serves as a potent stressor, producing persistent dysregulation of brain reward and stress systems beyond normal homeostatic limits. This progressive dysfunctional (allostatic) state is characterized by changes in neuroendocrine and brain stress pathways that underlie expression of withdrawal symptoms that reflect a negative affective state (dysphoria, anxiety), as well as increased motivation to self-administer alcohol. This review highlights literature supportive of this theoretical framework for alcohol addiction. In particular, evidence for stress-related neural, physiological, and behavioral changes associated with chronic alcohol exposure and withdrawal experience is presented. Additionally, this review focuses on the effects of chronic alcohol-induced changes in several pro-stress neuropeptides (corticotropin-releasing factor, dynorphin) and anti-stress neuropeptide systems (nocicepton, neuropeptide Y, oxytocin) in contributing to the stress, negative emotional, and motivational consequences of chronic alcohol exposure. Studies involving use of animal models have significantly increased our understanding of the dynamic stress-related physiological mechanisms and psychological underpinnings of alcohol addiction. This, in turn, is crucial for developing new and more effective therapeutics for treating excessive, harmful drinking, particularly stress-enhanced alcohol consumption. This article is part of the Special Issue entitled "Alcoholism".

A Review of the Benefits of Nature Experiences: More Than Meets the Eye

Evidence that experiences of nature can benefit people has accumulated rapidly. Yet perhaps because of the domination of the visual sense in humans, most research has focused on the visual aspects of nature experiences. However, humans are multisensory, and it seems likely that many benefits are delivered through the non-visual senses and these are potentially avenues through which a physiological mechanism could occur. Here we review the evidence around these lesser studied sensory pathways—through sound, smell, taste, touch, and three non-sensory pathways. Natural sounds and smells underpin experiences of nature for many people, and this may well be rooted in evolutionary psychology. Tactile experiences of nature, particularly beyond animal petting, are understudied yet potentially fundamentally important. Tastes of nature, through growing and consuming natural foods, have been linked with a range of health and well-being benefits. Beyond the five senses, evidence is emerging for other non-visual pathways for nature experiences to be effective. These include ingestion or inhalation of phytoncides, negative air ions and microbes. We conclude that (i) these non-visual avenues are potentially important for delivering benefits from nature experiences; (ii) the evidence base is relatively weak and often based on correlational studies; and (iii) deeper exploration of these sensory and non-sensory avenues is needed.

Alcohol Consumption Decreases Oxytocin Neurons in the Anterior Paraventricular Nucleus of the Hypothalamus in Prairie Voles

BACKGROUND

Alcohol use disorders are associated with dysfunctional social relationships and stress responses. The neuropeptides oxytocin (OT) and vasopressin (AVP) are known to orchestrate or mediate many aspects of social behavior, stress responses, and ingestive behaviors. Because of the overlap between the effects of alcohol and the roles of OT and AVP, we sought to determine whether alcohol consumption altered expression of OT and AVP in the paraventricular nucleus (PVN) of the hypothalamus, one of the key sites for OT and AVP synthesis.

METHODS

Pair-housed adult male prairie voles were allowed to consume 15% ethanol versus water in the home cage continuously (Continuous-Access [CA] group) or every other day for 4 hours (Intermittent-Access [IA] group). Control animals never had access to alcohol. After 7 weeks, animals were sacrificed and their brains were removed and immunohistochemical analysis of OT- and AVP-immunopositive neurons was performed.

RESULTS

OT-immunopositive neurons were significantly decreased in the anterior PVN in the CA but not IA group, relative to Control animals, suggesting that continuous alcohol consumption decreases the number of OT neurons. There was no effect of alcohol consumption on posterior PVN OT neurons, and no effect on PVN AVP neurons.

CONCLUSIONS

These data show that continuous-access voluntary alcohol consumption is associated with decreased OT neurons in the anterior PVN, suggesting that alcohol-induced alterations in the OT system should be investigated as a mechanism for alcohol-related changes in social behavior, stress responses, and exacerbation of alcohol use disorders.

Oxytocin receptor neurotransmission in the dorsolateral bed nucleus of the stria terminalis facilitates the acquisition of cued fear in the fear-potentiated startle paradigm in rats

Oxytocin (OT) is a hypothalamic neuropeptide that modulates fear and anxiety-like behaviors. Dorsolateral bed nucleus of the stria terminalis (BNSTdl) plays a critical role in the regulation of fear and anxiety, and expresses high levels of OT receptor (OTR). However, the role of OTR neurotransmission within the BNSTdl in mediating these behaviors is unknown. Here, we used adult male Sprague-Dawley rats to investigate the role of OTR neurotransmission in the BNSTdl in the modulation of the acoustic startle response, as well as in the acquisition and consolidation of conditioned fear using fear potentiated startle (FPS) paradigm. Bilateral intra-BNSTdl administration of OT (100 ng) did not affect the acquisition of conditioned fear response. However, intra-BNSTdl administration of specific OTR antagonist (OTA), (d(CH2)51, Tyr(Me)2, Thr4, Orn8, des-Gly-NH29)-vasotocin, (200 ng), prior to the fear conditioning session, impaired the acquisition of cued fear, without affecting a non-cued fear component of FPS. Neither OTA, nor OT affected baseline startle or shock reactivity during fear conditioning. Therefore, the observed impairment of cued fear after OTA infusion resulted from the specific effect on the formation of cued fear. In contrast to the acquisition, neither OTA nor OT affected the consolidation of FPS, when administered after the completion of fear conditioning session. Taken together, these results reveal the important role of OTR neurotransmission in the BNSTdl in the formation of conditioned fear to a discrete cue. This study also highlights the role of the BNSTdl in learning to discriminate between threatening and safe stimuli.

Associations Between Vocal Symptoms and Genetic Variants in the Oxytocin Receptor and Arginine Vasopressin 1A Receptor Gene

PURPOSE

Oxytocin and arginine vasopressin are associated with different aspects of the stress response. As stress is regarded as a risk factor for vocal symptoms, we wanted to explore the association between the oxytocin receptor gene (OXTR) and arginine vasopressin 1A receptor gene (AVPR1A) single-nucleotide polymorphisms (SNPs) and vocal symptoms. We also wanted to explore whether such effects might be mediated by cortisol because oxytocin and vasopressin are associated with cortisol levels.

METHOD

A population-based sample (N = 657) of Finnish twins (born 1961-1989) completed a web questionnaire on the occurrence of vocal symptoms. A total of 170 participants submitted saliva samples for hormone analysis. A total of 20 OXTR and AVPR1A SNPs were analyzed.

RESULTS

Three OXTR polymorphisms (rs2270465, rs2268493, rs7632287) and 2 AVPR1A polymorphisms (rs1587097, rs1042615) showed nominal effects (p < .05) on vocal symptoms, of which 1 (rs1587097) remained significant after correcting for multiple testing (p = .003). We found potential mediation of the effect of the OXTR rs2268493 polymorphism on vocal symptoms through levels of cortisol.

CONCLUSIONS

The associations between variants of OXTR and AVPR1A and vocal symptoms indicate that oxytocin and vasopressin might influence vocal symptoms. The effect of oxytocin seems to be partly mediated through cortisol actions.

Oxytocin attenuates social and non-social avoidance: Re-thinking the social specificity of Oxytocin

Re-examining decades of the social construal of Oxytocin, the General Approach-Avoidance Hypothesis of Oxytocin (GAAO) predicts that Oxytocin will modulate responding to emotionally-evocative and personally-relevant social and non-social stimuli due to its action on the neural substrate of approach and avoidance motivation. We report the first critical experimental test of GAAO predictions by means of a double-blind intra-nasal administration of Oxytocin vs. placebo in 90 healthy adults (N=90, 50% women). As predicted, we found that among men and women for whom negative emotion (anxious arousal) is motivationally-relevant, intra-nasal administration of Oxytocin reduced behavioral avoidance of emotionally-evocative negatively-valenced social and non-social stimuli, but not closely matched emotionally-neutral stimuli. Findings cannot be explained by extant social theories of Oxytocin. We discuss the implications of the present findings for basic and translational clinical Oxytocin research.

Rol Modulador de la Oxitocina en la Interacción Social y el Estrés Social

La Oxitocina es un neuropéptido conocido por facilitar funciones del sistema nervioso periférico, relacionadas específicamente con el sistema reproductivo. Sin embargo, en las últimas décadas se ha reconocido la función moduladora de la Oxitocina en el comportamiento social, a través de su liberación en el sistema nervioso central. Así mismo, estudios han mencionado que la Oxitocina es un potencial ansiolítico cuando un individuo ha sido sometido a estrés social. Por lo tanto, el objetivo de esta revisión es presentar una caracterización de la Oxitocina y su relación con distintas formas de interacción social y el estrés social; a través de los resultados presentados en distintos estudios, tanto en modelos animales como en humanos. Además, se intenta mostrar la importancia de continuar con el estudio de la Oxitocina, dados los posibles vacíos teóricos y experimentales existentes, teniendo en cuenta las potenciales cualidades ansiolíticas de esta hormona.

Effects of social deprivation on social and depressive-like behaviors and the numbers of oxytocin expressing neurons in rats

Social isolation is a known stressor that negatively impacts the well-being of social species. In rodents, social deprivation experienced either before or after weaning profoundly impacts adult behavioral and neuroendocrine profiles. This study compared the effects of post-natal and post-weaning social deprivation on behavioral profiles and hypothalamic oxytocin (OT) neurons. Male and female Sprague-Dawley rats were assigned to two post-natal groups, maternally separated (MS) or non-MS. MS pups were separated from their mothers for 4h daily during post-natal days 2-21 while non-MS litters remained undisturbed. Animals were then weaned and assigned to single or group housing conditions (SH/GH). Social behaviors were evaluated two weeks later and at 2-3 months of age, depressive-like behavioral profiles were assessed using the forced swim and sucrose preference tests. Animals were euthanized, and hypothalamic OT neurons were quantified. Post-weaning isolation significantly impacted behavioral profiles, with SH animals displaying more social behaviors than GH animals. SH animals also exhibited more immobility behavior in the forced swim test and a decreased sucrose preference. Effects of sex and MS were relatively limited. Correlation analyses revealed an inverse relationship between the display of antagonistic social behaviors and the numbers of OT cells in the anterior parvicellular division of the paraventricular nucleus (PVNap). There were no correlations between numbers of OT neurons and prosocial or depressive-like behaviors. Our results demonstrate a rapid and persistent disruption of behaviors in SH animals and suggest that some of these effects may be associated with numbers of OT neurons in the PVNap.

Mechanisms of social buffering of fear in zebrafish

Some humans thrive whereas others resign when exposed to threatening situations throughout life. Social support has been identified as an important modulator of these discrepancies in human behaviour, and other social animals also exhibit phenomena in which individuals recover better from aversive events when conspecifics are present - aka social buffering. Here we studied social buffering in zebrafish, by exposing focal fish to an aversive stimulus (alarm substance - AS) either in the absence or presence of conspecific cues. When exposed to AS in the presence of both olfactory (shoal water) and visual (sight of shoal) conspecific cues, focal fish exhibited a lower fear response than when tested alone, demonstrating social buffering in zebrafish. When separately testing each cue's effectiveness, we verified that the visual cue was more effective than the olfactory in reducing freezing in a persistent threat scenario. Finally, we verified that social buffering was independent of shoal size and coincided with a distinct pattern of co-activation of brain regions known to be involved in mammalian social buffering. Thus, this study suggests a shared evolutionary origin for social buffering in vertebrates, bringing new evidence on the behavioural, sensory and neural mechanisms underlying this phenomenon.

Forced swimming-induced oxytocin release into blood and brain: Effects of adrenalectomy and corticosterone treatment

The oxytocin (OXT) system is functionally linked to the HPA axis in a reciprocal and complex manner. Certain stressors are known to cause the simultaneous release of OXT and adrenocorticotrophic hormone (ACTH) followed by corticosterone (CORT). Furthermore, brain OXT attenuates ACTH and CORT responses. Although there are some indications of CORT influencing OXT neurotransmission, specific effects of CORT on neurohypophyseal or intra-hypothalamic release of OXT have not been studied in detail. In the present set of experiments, adult male rats were adrenalectomized (ADX) or sham-operated and fitted with a jugular vein catheter and/or microdialysis probe targeting the hypothalamic paraventricular nucleus (PVN). Blood samples and dialysates were collected before and after forced swimming (FS) and analyzed for CORT, ACTH and AVP concentrations (in plasma) and OXT concentrations (in plasma and dialysates). Experimental treatments included acute infusion of CORT (70 or 175μg/kg i.v.) 5min prior to FS, or subcutaneous placement of 40% CORT pellets resulting in stable CORT levels in the normal basal range. Although ADX did not alter basal OXT concentrations either in plasma or in microdialysates from the PVN, it did cause an exaggerated peripheral secretion of OXT and a blunted intra-PVN release of OXT in response to FS. CORT pellets did not influence either of these ADX-induced effects, while acute infusion of 175μg/kg CORT rescued the stress-induced rise in OXT release within the PVN and modestly increased peripheral OXT secretion. In conclusion, these results indicate that CORT regulates both peripheral and intracerebral OXT release, but in an independent manner. Whereas the peripheral secretion of OXT occurs simultaneously to HPA axis activation in response to FS and is modestly influenced by CORT, HPA axis activation and circulating CORT strongly contribute to the stress-induced stimulation of OXT release within the PVN.

The neurobiological causes and effects of alloparenting

Alloparenting, defined as care provided by individuals other than parents, is a universal behavior among humans that has shaped our evolutionary history and remains important in contemporary society. Dysfunctions in alloparenting can have serious and sometimes fatal consequences for vulnerable infants and children. In spite of the importance of alloparenting, they still have much to learn regarding the underlying neurobiological systems governing its expression. Here, they review how a lack of alloparental behavior among traditional laboratory species has led to a blind spot in our understanding of this critical facet of human social behavior and the relevant neurobiology. Based on what is known, they draw from model systems ranging from voles to meerkats to primates to describe a conserved set of neuroendocrine mechanisms supporting the expression of alloparental care. In this review we describe the neurobiological and behavioral prerequisites, ontogeny, and consequences of alloparental care. Lastly, they identified several outstanding topics in the area of alloparental care that deserve further research efforts to better advance human health and wellbeing. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 214-232, 2017.

Approaches Mediating Oxytocin Regulation of the Immune System

The hypothalamic neuroendocrine system is mainly composed of the neural structures regulating hormone secretion from the pituitary gland and has been considered as the higher regulatory center of the immune system. Recently, the hypothalamo-neurohypophysial system (HNS) emerged as an important component of neuroendocrine–immune network, wherein the oxytocin (OT)-secreting system (OSS) plays an essential role. The OSS, consisting of OT neurons in the supraoptic nucleus, paraventricular nucleus, their several accessory nuclei and associated structures, can integrate neural, endocrine, metabolic, and immune information and plays a pivotal role in the development and functions of the immune system. The OSS can promote the development of thymus and bone marrow, perform immune surveillance, strengthen immune defense, and maintain immune homeostasis. Correspondingly, OT can inhibit inflammation, exert antibiotic-like effect, promote wound healing and regeneration, and suppress stress-associated immune disorders. In this process, the OSS can release OT to act on immune system directly by activating OT receptors or through modulating activities of other hypothalamic–pituitary–immune axes and autonomic nervous system indirectly. However, our understandings of the role of the OSS in neuroendocrine regulation of immune system are largely incomplete, particularly its relationship with other hypothalamic–pituitary–immune axes and the vasopressin-secreting system that coexists with the OSS in the HNS. In addition, it remains unclear about the relationship between the OSS and peripherally produced OT in immune regulation, particularly intrathymic OT that is known to elicit central immunological self-tolerance of T-cells to hypophysial hormones. In this work, we provide a brief review of current knowledge of the features of OSS regulation of the immune system and of potential approaches that mediate OSS coordination of the activities of entire neuroendocrine–immune network.

The Multidimensional Therapeutic Potential of Targeting the Brain Oxytocin System for the Treatment of Substance Use Disorders

The neuropeptide oxytocin is released both into the blood and within the brain in response to reproductive stimuli, such as birth, suckling and sex, but also in response to social interaction and stressors. Substance use disorders, or addictions, are chronic, relapsing brain disorders and are one of the major causes of global burden of disease. Unfortunately, current treatment options for substance use disorders are extremely limited and a treatment breakthrough is sorely needed. There is mounting preclinical evidence that targeting the brain oxytocin system may provide that breakthrough. Substance use disorders are characterised by a viscous cycle of bingeing and intoxication, followed by withdrawal and negative affect, and finally preoccupation and anticipation that triggers relapse and further consumption. Administration of oxytocin has been shown to have a potential therapeutic benefit at each stage of this addiction cycle for numerous drugs of abuse. This multidimensional therapeutic utility is likely due to oxytocin's interactions with key biological systems that underlie the development and maintenance of addiction. Only a few human trials of oxytocin in addicted populations have been completed with the results thus far being mixed. There are numerous other trials underway, and the results are eagerly awaited. However, the ability to fully harness the potential therapeutic benefit of targeting the brain oxytocin system may depend on the development of molecules that selectively stimulate the oxytocin system, but that have superior pharmacokinetic properties to oxytocin itself.

Oxytocin in the socioemotional brain: implications for psychiatric disorders

The neuropeptide oxytocin (OXT), highly conserved during evolution, is an important modulator of social and emotional processes across many species. During the last decade, a large body of literature has revealed its effects on different aspects of social behavior, including social stress and anxiety, social memory, affiliation and bonding, emotion recognition, mentalizing, empathy, and interpersonal trust. In addition, as impairments in these social domains can be observed in a number of neuropsychiatric disorders, such as autism, social anxiety disorder, depression, schizophrenia, and borderline personality disorder, the role of OXT in mental disorders and their treatment has been intensively studied. The present paper gives a short overview of these lines of research and shows how OXT has become a promising target for novel treatment approaches for mental disorders characterized by social impairments.

Neuropeptide Regulation of Social Attachment: The Prairie Vole Model

Social attachments are ubiquitous among humans and integral to human health. Although great efforts have been made to elucidate the neural underpinnings regulating social attachments, we still know relatively little about the neuronal and neurochemical regulation of social attachments. As a laboratory animal research model, the socially monogamous prairie vole (Microtus ochrogaster) displays behaviors paralleling human social attachments and thus has provided unique insights into the neural regulation of social behaviors. Research in prairie voles has particularly highlighted the significance of neuropeptidergic regulation of social behaviors, especially of the roles of oxytocin (OT) and vasopressin (AVP). This article aims to review these findings. We begin by discussing the role of the OT and AVP systems in regulating social behaviors relevant to social attachments, and thereafter restrict our discussion to studies in prairie voles. Specifically, we discuss the role of OT and AVP in adult mate attachments, biparental care, social isolation, and social buffering as informed by studies utilizing the prairie vole model. Not only do these studies offer insight into social attachments in humans, but they also point to dysregulated mechanisms in several mental disorders. We conclude by discussing these implications for human health. © 2017 American Physiological Society. Compr Physiol 7:81-104, 2017.

Oxytocin attenuates aversive response to nicotine and anxiety-like behavior in adolescent rats

Initial tobacco use is initiated with rewarding and aversive properties of nicotine and aversive response to nicotine plays a critical role in nicotine dependency. Decrease of nicotine aversion increases the nicotine use that causes behavioral and neuronal changes of animals. Oxytocin influences drug abuse and reciprocally affect vulnerability to drug use. To assess the effect of oxytocin on initial nicotine aversion and anxiety, we examined voluntary oral nicotine intake and anxiety-like behavior following oxytocin treatment in adolescent rats. Sprague-Dawley male rats (4 weeks old) were used. For oxytocin administration, rats were injected subcutaneously with saline or oxytocin (0.01, 0.1 and 1mg/kg) according to the assigned groups. Voluntary oral nicotine consumption test was performed by two bottle free-choice paradigm. To examine anxiety-like behavior in rats, we performed a light/dark box test. Oxytocin not only significantly increased the nicotine intake but also alleviated nicotine aversion after acclimation to nicotine solution in a concentration dependent manner. Meanwhile, oxytocin significantly reduced anxiety-like behavior. We suggest that oxytocin itself mitigates aversive response toward initial nicotine intake and anxiety-like behavior. These results widen the psychophysiological perspective on oxytocin for better understanding of nicotine addiction related behaviors influenced by diverse social factors.

A meta-analytic review of the correlation between peripheral oxytocin and cortisol concentrations

The stress dampening effects of exogenous oxytocin in humans have been well documented. However, the relation between endogenous oxytocin and cortisol is poorly understood. We conducted a meta-analysis on the correlation between oxytocin and cortisol levels measured at baseline (k=24, N=739). The effect size for the baseline correlation statistic was small (Pearson r=0.163, p=0.008), with high heterogeneity (I²=67.88%). Moderation analysis revealed that studies where participants anticipated an experimental manipulation evidenced a greater positive correlation compared to those that did not (Pearson r=0.318, p=0.006). A supplementary analysis including additional studies indicated that oxytocin levels in unextracted samples were 60 times higher when using this questionable practice. The findings suggest that the interplay between oxytocin and cortisol is dynamic and sensitive to the anticipation of stress or novelty. Furthermore, extraction of oxytocin appears to be an essential methodological practice.

Cocaine abstinence induces emotional impairment and brain region-specific upregulation of the oxytocin receptor binding

The key problem in treating cocaine addiction is the maintenance of a drug-free state as negative emotional symptoms during abstinence often trigger relapse. The mechanisms underpinning the emotional dysregulation during abstinence are currently not well-understood. There is evidence suggesting a role of the neuropeptide oxytocin in the modulation of drug addiction processes. However, its involvement during long-term abstinence from cocaine use remains unclear. In this study, we aimed to behaviourally characterize a mouse model of long-term cocaine withdrawal and assess the effect of chronic cocaine administration and long-term cocaine abstinence on the central oxytocinergic system and the hypothalamic-pituitary-adrenal axis. Fourteen-day escalating-dose cocaine administration (3 × 15-30 mg/kg/day) and 14-day withdrawal increased plasma corticosterone levels and oxytocin receptor (OTR) binding in piriform cortex, lateral septum and amygdala. A specific cocaine withdrawal-induced increase in OTR binding was observed in the medial septum. These biochemical alterations occurred concomitantly with the emergence of memory impairment, contextual psychomotor sensitization and an anhedonic and anxiogenic phenotype during withdrawal. Our study established a clear relationship between cocaine abstinence and emotional impairment in a novel translationally relevant model of cocaine withdrawal and demonstrated for the first time brain region-specific neuroadaptations of the oxytocin system, which may contribute to abstinence-induced negative emotional state.

The neurocircuitry involved in oxytocin modulation of methamphetamine addiction

The role of oxytocin in attenuating the abuse of licit and illicit drugs, including the psychostimulant methamphetamine, has been examined with increased ferocity in recent years. This is largely driven by the potential application of oxytocin as a pharmacotherapy. However, the neural mechanisms by which oxytocin modulates methamphetamine abuse are not well understood. Recent research identified an important role for the accumbens core and subthalamic nucleus in this process, which likely involves an interaction with dopamine, glutamate, GABA, and vasopressin. In addition to providing an overview of methamphetamine, the endogenous oxytocin system, and the effects of exogenous oxytocin on drug abuse, we propose a neural circuit through which exogenous oxytocin modulates methamphetamine abuse, focusing on its interaction with neurochemicals within the accumbens core and subthalamic nucleus. A growing understanding of exogenous oxytocin effects at a neurochemical and neurobiological level will assist in its evaluation as a pharmacotherapy for drug addiction.

Ewes With Divergent Cortisol Responses to ACTH Exhibit Functional Differences in the Hypothalamo-Pituitary-Adrenal (HPA) Axis

Within any population, the cortisol response to ACTH covers a considerable range. High responders (HRs) exhibit a greater cortisol secretory response to stress or ACTH, compared with individuals classified as low cortisol responders (LRs). We administered ACTH (0.2 μg/kg, iv) to 160 female sheep and selected subpopulations of animals as LR and HR. In the present study, we aimed to characterize the hypothalamo-pituitary-adrenal axis in HR and LR and to identify factors that underlie the differing cortisol responses to ACTH. Hypothalami, pituitaries, and adrenals were collected from nonstressed HR and LR ewes. Expression of genes for CRH, arginine vasopressin (AVP), oxytocin, glucocorticoid receptor, and mineralocorticoid receptor were measured by in situ hybridization in the paraventricular nucleus of the hypothalamus, and proopiomelanocortin (POMC) gene expression was measured in the anterior pituitary. Expression of CRH, AVP, and POMC was higher in HR, with no differences in either glucocorticoid receptor or mineralocorticoid receptor expression. Oxytocin expression was greater in LR. In the adrenal gland, real-time PCR analysis indicated that expression of the ACTH receptor and a range of steroidogenic enzymes was similar in HR and LR. Adrenal weights, the cortex to medulla ratio and adrenal cortisol content were also similar in LR and HR. In conclusion, LR and HR display innate differences in the steady-state expression of CRH, AVP, oxytocin, and POMC, indicating that selection for cortisol responsiveness identifies distinct subpopulations that exhibit innate differences in the gene expression/function of hypothalamo-pituitary-adrenal axis markers.

Mood, Food, and Fertility: Adaptations of the Maternal Brain

Successfully rearing young places multiple demands on the mammalian female. These are met by a wide array of alterations in maternal physiology and behavior that are coordinated with the needs of the developing young, and include adaptations in neuroendocrine systems not directly involved in maternal behavior or lactation. In this article, attenuations in the behavioral and neuroendocrine responses to stressors, the alterations in metabolic pathways facilitating both increased food intake and conservation of energy, and the changes in fertility that occur postpartum are described. The mechanisms underlying these processes as well as the factors that contribute to them and the relative contributions of these stimuli at different times postpartum are also reviewed. The induction and maintenance of the adaptations observed in the postpartum maternal brain are dependent on mother-young interaction and, in most cases, on suckling stimulation and its consequences for the hormonal profile of the mother. The peptide hormone prolactin acting on receptors within the brain makes a major contribution to changes in metabolic pathways, suppression of fertility and the attenuation of the neuroendocrine response to stress during lactation. Oxytocin is also released, both into the circulation and in some hypothalamic nuclei, in response to suckling stimulation and this hormone has been implicated in the decrease in anxiety behavior seen in the early postpartum period. The relative importance of these hormones changes across lactation and it is becoming increasingly clear that many of the adaptations to motherhood reviewed here reflect the outcome of multiple influences. © 2016 American Physiological Society. Compr Physiol 6:1493-1518, 2016.

Nucleus accumbens lentiviral-mediated gain of function of the oxytocin receptor regulates anxiety- and ethanol-related behaviors in adult mice

Anxiety is believed to influence ethanol use human in alcoholics. Studies using laboratory animals suggested an interaction between oxytocin and the behavioral effects of ethanol. Our previous study implicated a potential role for the oxytocin receptor (OxtR) in regulating ethanol-conditioned place preference. Here, we examined anxiety and the behavioral responses to ethanol in C57BL/6 mice stereotaxically injected in the nucleus accumbens (NAcc) with lentiviral vectors expressing an empty vector (Mock) or the OxtR cDNA. For anxiety we used the elevated-plus maze, the open-field and the marble-burying tests and for ethanol we used the two-bottle choice paradigm, the wire-hanging and ethanol-induced loss-of-righting-reflex tests. We found that, compared to Mock, OxtR overexpression led to anxiolytic-like behavior without altering spontaneous locomotor activity. Most importantly, we found that, relative to Mock controls, increased expression of the OxtR in the NAcc led to decreased ethanol consumption and preference in the two-bottle choice protocol and increased resistance to ethanol-induced sedation. We also compared the consequence of OxtR modulation on the consumption and preference of saccharin and quinine and found that the two experimental groups did not differ for any tastant. These results provide further evidence that the oxytocin system contributes to the regulation of ethanol drinking and sensitivity and position OxtR as a central molecular mediator of ethanol's effects within the mesolimbic system. Taken together, the current findings suggest that OxtR manipulation may be a relevant strategy to address ethanol use disorders.

Effects of intranasal oxytocin on steroid hormones in men and women

BACKGROUND

Recent interest in the social and cognitive effects of intranasal oxytocin prompts a need for understanding its physiological effects in humans. Few studies have examined the effects of intranasal oxytocin on steroid hormones. Filling this gap is especially important given the evidence that steroid hormones participate in some of the same behavioral functions as oxytocin, e.g. in stress, processing of emotional stimuli, aggression, trust, empathy, and parental care.

METHODS

In randomized, double-blind experiments, we administered oxytocin (24 IU) or saline placebo to 97 healthy participants. Saliva samples were collected before and at several time points after the oxytocin/placebo administration to assess the levels of cortisol, progesterone, and testosterone.

RESULTS

Oxytocin had no effects on testosterone, progesterone, or cortisol in women or men.

CONCLUSION

Acute intranasal oxytocin does not affect the levels of cortisol, testosterone or progesterone in humans, at least in the absence of a stressful context. These data suggest that acute oxytocin does not have a direct impact on the human hypothalamic-pituitary-adrenal or hypothalamic-pituitary-gonadal axes under nonstressful circumstances. This knowledge helps rule out potential mechanisms for some of the effects of oxytocin in humans and adds to the generally limited body of knowledge on the basic physiological or psychological effects of intranasal oxytocin in human beings.

Animal Assisted Therapy (AAT) Program As a Useful Adjunct to Conventional Psychosocial Rehabilitation for Patients with Schizophrenia: Results of a Small-scale Randomized Controlled Trial

Currently, one of the main objectives of human-animal interaction research is to demonstrate the benefits of animal assisted therapy (AAT) for specific profiles of patients or participants. The aim of this study is to assess the effect of an AAT program as an adjunct to a conventional 6-month psychosocial rehabilitation program for people with schizophrenia. Our hypothesis is that the inclusion of AAT into psychosocial rehabilitation would contribute positively to the impact of the overall program on symptomology and quality of life, and that AAT would be a positive experience for patients. To test these hypotheses, we compared pre-program with post-program scores for the Positive and Negative Syndrome Scale (PANSS) and the EuroQoL-5 dimensions questionnaire (EuroQol-5D), pre-session with post-session salivary cortisol and alpha-amylase for the last four AAT sessions, and adherence rates between different elements of the program. We conducted a randomized, controlled study in a psychiatric care center in Spain. Twenty-two institutionalized patients with chronic schizophrenia completed the 6-month rehabilitation program, which included individual psychotherapy, group therapy, a functional program (intended to improve daily functioning), a community program (intended to facilitate community reintegration) and a family program. Each member of the control group (n = 8) participated in one activity from a range of therapeutic activities that were part of the functional program. In place of this functional program activity, the AAT-treatment group (n = 14) participated in twice-weekly 1-h sessions of AAT. All participants received the same weekly total number of hours of rehabilitation. At the end of the program, both groups (control and AAT-treatment) showed significant improvements in positive and overall symptomatology, as measured with PANSS, but only the AAT-treatment group showed a significant improvement in negative symptomatology. Adherence to the AAT-treatment was significantly higher than overall adherence to the control group's functional rehabilitation activities. Cortisol level was significantly reduced after participating in an AAT session, which could indicate that interaction with the therapy dogs reduced stress. In conclusion, the results of this small-scale RCT suggest that AAT could be considered a useful adjunct to conventional psychosocial rehabilitation for people with schizophrenia.

Effects of oxytocin on adreno-medullary catecholamine synthesis, uptake and storage in rats exposed to chronic isolation stress

PURPOSE/AIM

The adreno-medullar system represents one of the main systems involved in the response to stressful events. The neuropeptide oxytocin, is highly sensitive to the social environment, and regulates autonomic function. Adreno-medullary activity is dependent on the synthesis of catecholamine, its reuptake, release, degradation and vesicular transport. A direct influence of oxytocin on catecholamine synthesizing enzyme and transports in animals exposed to chronic social isolation stress has not been studied yet.

MATERIALS AND METHODS

In the present study, we examined the effect of chronic oxytocin treatment on the level of plasma catecholamine and its content, mRNA and protein levels of tyrosine hydroxylase (TH), noradrenaline transporter (NET) as well as vesicular monoamine transporter 2 (VMAT2) in the adrenal medulla of socially isolated rats.

RESULTS

Our results show that, by the end of 12 weeks, social isolation did not produce any significant changes in catecholamine content but increased plasma catecholamine level and synthesis in the adrenal medulla. Oxytocin treatment had no further effect either on catecholamine synthesis or content in socially stressed animals whereas a significant elevation of plasma norepinephrine and epinephrine were reduced. On the other hand, chronic isolation caused a significant increase in VMAT2 and decrease in NET protein levels. Oxytocin treatment brought about an increase in protein levels of NET and its return to the levels of control group. Besides, it further increases VMAT2 protein levels in the adrenal medulla of individually housed rats.

CONCLUSION

The present results show that peripheral oxytocin treatment enhances catecholamine uptake and storage in the adrenal medulla of chronically isolated animals.