The impact of oxytocin on stress: the role of sex

Facing stress and inflammation: From the cell to the planet

As identified in 1936 by Hans Selye, stress is shaping diseases through the induction of inflammation. But inflammation display some yin yang properties. On one hand inflammation is merging with the innate immune response aimed to fight infectious or sterile insults, on the other hand inflammation favors chronic physical or psychological disorders. Nature has equipped the cells, the organs, and the individuals with mediators and mechanisms that allow them to deal with stress, and even a good stress (eustress) has been associated with homeostasis. Likewise, societies and the planet are exposed to stressful settings, but wars and global warming suggest that the regulatory mechanisms are poorly efficient. In this review we list some inducers of the physiological stress, psychologic stress, societal stress, and planetary stress, and mention some of the great number of parameters which affect and modulate the response to stress and render it different from an individual to another, from the cellular level to the societal one. The cell, the organ, the individual, the society, and the planet share many stressors of which the consequences are extremely interconnected ending in the domino effect and the butterfly effect.

The interplay of oxytocin and sex hormones

The neuropeptide oxytocin has historically been associated with reproduction and maternal behavior. However, more recent research has uncovered that oxytocin has a much wider range of roles in physiology and behavior. Despite the excitement surrounding potential therapeutical applications of intranasally administered oxytocin, the results of these intervention studies have been inconsistent. Various reasons for these mixed results have been proposed, which tend to focus on methodological issues, such as study design. While methodological issues are certainly important, emerging evidence suggests that the interaction between oxytocin and sex hormones may also account for these varied findings. To better understand the purpose and function of the interaction of oxytocin with sex hormones, with a focus on estrogens, progesterone, and testosterone, we conducted a comprehensive thematic review via four perspectives: evolutionary, developmental, mechanistic, and survival. Altogether, this synergistic approach highlights the critical function of sex hormone activity for accomplishing the diverse roles of oxytocin via the modulation of oxytocin release and oxytocin receptor activity, which is also likely to contribute to the heterogeneity of outcomes after oxytocin administration.

Neuromodulation of safety and surprise in the early stages of infant development: affective homeostatic regulation in bodily and mental functions

Developing a sense of internal safety and security depends mainly on others: numerous neuromodulators play a significant role in the homeostatic process, regulating the importance of proximity to a caregiver and experiencing feelings that enable us to regulate our interdependence with our conspecifics since birth. This array of neurofunctional structures have been called the SEPARATION DISTRESS system (now more commonly known as the PANIC/ GRIEF system). This emotional system is mainly involved in the production of depressive symptoms. The disruption of this essential emotional balance leads to the onset of feelings of panic followed by depression. We will focus on the neuropeptides that play a crucial role in social approach behavior in mammals, which enhance prosocial behavior and facilitate the consolidation of social bonds. We propose that most prosocial behaviors are regulated through the specific neuromodulators acting on salient intersubjective stimuli, reflecting an increased sense of inner confidence (safety) in social relationships. This review considers the neurofunctional link between the feelings that may ultimately be at the base of a sense of inner safety and the central neuromodulatory systems. This link may shed light on the clinical implications for the development of early mother-infant bonding and the depressive clinical consequences when this bond is disrupted, such as in post-partum depression, depressive feelings connected to, addiction, neurofunctional disorders, and psychological trauma.

Validity of mental and physical stress models

Different stress models are employed to enhance our understanding of the underlying mechanisms and explore potential interventions. However, the utility of these models remains a critical concern, as their validities may be limited by the complexity of stress processes. Literature review revealed that both mental and physical stress models possess reasonable construct and criterion validities, respectively reflected in psychometrically assessed stress ratings and in activation of the sympathoadrenal system and the hypothalamic-pituitary-adrenal axis. The findings are less robust, though, in the pharmacological perturbations' domain, including such agents as adenosine or dobutamine. Likewise, stress models' convergent- and discriminant validity vary depending on the stressors' nature. Stress models share similarities, but also have important differences regarding their validities. Specific traits defined by the nature of the stressor stimulus should be taken into consideration when selecting stress models. Doing so can personalize prevention and treatment of stress-related antecedents, its acute processing, and chronic sequelae. Further work is warranted to refine stress models' validity and customize them so they commensurate diverse populations and circumstances.

Modeling psychotic disorders: Environment x environment interaction

Schizophrenia is a major psychotic disorder with multifactorial etiology that includes interactions between genetic vulnerability and environmental risk factors. In addition, interplay of multiple environmental adversities affects neurodevelopment and may increase the individual risk of developing schizophrenia. Consistent with the two-hit hypothesis of schizophrenia, we review rodent models that combine maternal immune activation as the first hit with other adverse environmental exposures as the second hit. We discuss the strengths and pitfalls of the current animal models of environment x environment interplay and propose some future directions to advance the field.

The Role of Oxytocin in Early-Life-Stress-Related Neuropsychiatric Disorders

Early-life stress during critical periods of brain development can have long-term effects on physical and mental health. Oxytocin is a critical social regulator and anti-inflammatory hormone that modulates stress-related functions and social behaviors and alleviates diseases. Oxytocin-related neural systems show high plasticity in early postpartum and adolescent periods. Early-life stress can influence the oxytocin system long term by altering the expression and signaling of oxytocin receptors. Deficits in social behavior, emotional control, and stress responses may result, thus increasing the risk of anxiety, depression, and other stress-related neuropsychiatric diseases. Oxytocin is regarded as an important target for the treatment of stress-related neuropsychiatric disorders. Here, we describe the history of oxytocin and its role in neural circuits and related behaviors. We then review abnormalities in the oxytocin system in early-life stress and the functions of oxytocin in treating stress-related neuropsychiatric disorders.

Effect of Neurosteroids on Basal and Stress-Induced Oxytocin Secretion in Luteal-Phase and Pregnant Sheep

Oxytocin (OT) is a neuropeptide synthesized in the hypothalamic nuclei that modulates both behavioral and reproductive functions, associated with the increased neurosteroid synthesis in the brain. Therefore, the present study tested the hypothesis that manipulation of central neurosteroid levels could affect oxytocin synthesis and release in non-pregnant and pregnant sheep under both basal and stressful conditions. In Experiment 1, luteal-phase sheep were subjected to a series of intracerebroventricular (icv.) infusions of allopregnanolone (AL, 4 × 15 μg/60 μL/30 min) for 3 days. In Experiment 2, pregnant animals (4th month) received a series of infusions of the neurosteroid synthesis blocker, finasteride (4 × 25 μg/60 μL/30 min), conducted for 3 days. In non-pregnant sheep AL alone was shown to differentially modulate OT synthesis in basal conditions, and strongly inhibit OT response to stress (p < 0.001). In contrast, in pregnant animals, basal and stress-induced OT secretion was significantly (p < 0.001) increased during finasteride infusion compared to controls. In conclusion, we showed that neurosteroids were involved in the control of OT secretion in sheep, particularly under stress and pregnancy conditions and are part of an adaptive mechanism which is responsible for protecting and maintaining pregnancy in harmful situations.

Association between stressful life events and non-optimal lipid levels among women with hyperlipidaemia

AIMS

Psychological stress has been linked to lipid dysregulation with noticeable gender differences, but it remains unclear whether women are more susceptible to non-optimal lipid levels than men, when experiencing stressful life events. This study aims to examine the association between stressful life events and non-optimal lipid levels among persons with hyperlipidaemia and whether the association differs between men and women.

METHODS AND RESULTS

A nested case-control study was performed using data from the Wisconsin Sleep Cohort (WSC) Study from 2011 to 2015, including 224 participants with hyperlipidaemia and without a history of myocardial infarction or heart failure. Among them, 63 participants with non-optimal LDL cholesterol or triglyceride levels were identified as cases, and 161 participants with optimal LDL cholesterol and triglyceride levels were identified as controls. Cases and controls were traced back to their self-reported life events collected through the Retirement and Sleep Trajectories study during 2010-11. The association between stressful life events and non-optimal lipid levels was examined using multivariable logistic regression; confounding effects were addressed using propensity score weighting and Mahalanobis distance matching; gender differences were examined using subgroup analysis. Results showed that a higher number of stressful life events during 2010-11 was associated with greater odds of non-optimal lipid levels during 2011-15 (odds ratio = 1.45, P = 0.03) among women with hyperlipidaemia, whereas the association was not significant among men with hyperlipidaemia (P = 0.910).

CONCLUSION

Future studies are needed to examine the underlying mechanisms that explain gender differences in the association between stressful life events and non-optimal lipid levels.

REGISTRATION

ClinicalTrials.gov NCT00005557.

Mitigating the impact of adolescence isolation on the development of social anxiety: A potential role for oxytocin

Exposure to isolation can lead to the development of social anxiety disorder (SAD), which affects 13% of Americans. There are sex differences in the prevalence of anxiety disorders, as women experience higher rates of SAD relative to men. Importantly, isolation experienced during adolescence increases the likelihood of developing SAD in adulthood. Unfortunately, the current treatments for SAD are only effective in 50–65% of patients. As such, it is critical to identify therapeutic targets for the treatment and prevention of SAD, particularly in women. Here, we discuss the links between childhood isolation and adulthood SAD. Next, we examine the preclinical models used to study the impact of isolation on social anxiety-like behaviors in rodents. Increasing evidence from both clinical and pre-clinical studies suggests oxytocin signaling is a potential target to modify social anxiety-like behaviors. We present the evidence that sex hormones influence the oxytocin system. Finally, we highlight future directions for both clinical and pre-clinical studies to further evaluate the efficacy of oxytocin as a treatment for isolation-induced SAD.

Social buffering of the stress response: insights from fishes

Social buffering of stress refers to the effect of a social partner in reducing the cortisol or corticosterone response to a stressor. It has been well studied in mammals, particularly those that form pair bonds. Recent studies on fishes suggest that social buffering of stress also occurs in solitary species, gregarious species that form loose aggregations and species with well-defined social structures and bonds. The diversity of social contexts in which stress buffering has been observed in fishes holds promise to shed light on the evolution of this phenomenon among vertebrates. Equally, the relative simplicity of the fish brain is advantageous for identifying the neural mechanisms responsible for social buffering. In particular, fishes have a relatively small and simple forebrain but the brain regions that are key to social buffering, including the social behaviour network, the amygdala and the hypothalamic-pituitary-adrenal/interrenal axis, are functionally conserved across vertebrates. Thus, we suggest that insight into the mechanistic and evolutionary underpinnings of stress buffering in vertebrates can be gained from the study of social buffering of stress in fishes.

Oxytocin treatment improves dexamethasone‐induced depression‐like symptoms associated with enhancement of hippocampal CREB‐BDNF signaling in female mice

Aims

Chronic stress and glucocorticoid exposure are risk factors for depression. Oxytocin (OT) has been shown to have antistress and antidepressant‐like effects in male rodents. However, depression is twice as common in women than in men, and it remains unclear whether OT exerts antidepressant‐like effects in women with depression. Therefore, in this study, we investigated the therapeutic effect of chronic OT administration in a female mouse model of dexamethasone (DEX)‐induced depression.

Methods

Female C57BL/6J mice were administered saline (vehicle, s.c.), DEX (s.c.), or OT (i.p.) + DEX (s.c.) daily for 8 weeks, and then assessed for anxiety‐ and depression‐like behaviors. We also examined the hippocampal levels of phosphorylated cAMP response element‐binding protein (p‐CREB) and brain‐derived neurotrophic factor (BDNF), which are important mediators of the response to antidepressants.

Results

Simultaneous OT treatment blocked the adverse effects of DEX on emotional behaviors. Furthermore, it upregulated p‐CREB and BDNF in the hippocampus.

Conclusion

OT may exert antidepressant‐like effects by activating hippocampal CREB‐BDNF signaling in a female mouse model of depression.

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: An Old Hormone, A Novel Psychotropic Drug And Possible Use In Treating Psychiatric Disorders

BACKGROUND

Oxytocin is a nonapeptide synthesized in the paraventricular and supraoptic nuclei of the hypothalamus. Historically, this molecule has been involved as a key factor in the formation of infant attachment, maternal behavior and pair bonding and, more generally, in linking social signals with cognition, behaviors and reward. In the last decades, the whole oxytocin system has gained a growing interest as it was proposed to be implicated in etiopathogenesis of several neurodevelopmental and neuropsychiatric disorders.

METHODS

With the main goal of an in-depth understanding of the oxytocin role in the regulation of different functions and complex behaviors as well as its intriguing implications in different neuropsychiatric disorders, we performed a critical review of the current state of art. We carried out this work through PubMed database up to June 2021 with the search terms: 1) "oxytocin and neuropsychiatric disorders"; 2) "oxytocin and neurodevelopmental disorders"; 3) "oxytocin and anorexia"; 4) "oxytocin and eating disorders"; 5) "oxytocin and obsessive-compulsive disorder"; 6) "oxytocin and schizophrenia"; 7) "oxytocin and depression"; 8) "oxytocin and bipolar disorder"; 9) "oxytocin and psychosis"; 10) "oxytocin and anxiety"; 11) "oxytocin and personality disorder"; 12) "oxytocin and PTSD".

RESULTS

Biological, genetic, and epigenetic studies highlighted quality and quantity modifications in the expression of oxytocin peptide or in oxytocin receptor isoforms. These alterations would seem to be correlated with a higher risk of presenting several neuropsychiatric disorders belonging to different psychopathological spectra. Collaterally, the exogenous oxytocin administration has shown to ameliorate many neuropsychiatric clinical conditions.

CONCLUSION

Finally, we briefly analyzed the potential pharmacological use of oxytocin in patient with severe symptomatic SARS-CoV-2 infection due to its anti-inflammatory, anti-oxidative and immunoregulatory properties.

Effects of Chronic and Acute Intranasal Oxytocin Treatments on Temporary Social Separation in Adult Titi Monkeys (Plecturocebus cupreus)

In socially monogamous titi monkeys, involuntary separation from a pair mate can produce behavioral distress and increased cortisol production. The neuropeptide oxytocin (OXT) is thought to play an important role in the separation response of pair-bonded species. Previous studies from our lab have shown that chronic intranasal oxytocin (IN OXT) during development can have long-term effects on adult social behavior. In the current study, we examined the chronic and acute effects of IN OXT or Saline (SAL) on the subjects’ response to a brief separation from their pair mates. Subjects with a history of chronic IN OXT or SAL treatment during development received a single dose of OXT or SAL as adults 30 min before being separated from their pair mate. Chronic treatment consisted of a daily dose of IN OXT (0.8 IU/kg) or SAL (control) from 12 to 18 months of age. Subjects (N = 29) were introduced to a pair mate at 30 months of age. After the pairs had cohabitated for 5 months, pairs underwent two “Brief Separation” (OXT and SAL) and two “Non-Separation” (OXT and SAL) test sessions. Vocalizations and locomotion were measured as behavioral indices of agitation or distress during the Brief Separation and Non-Separation periods (30 min each). We collected blood samples after the Brief Separation and Non-Separation periods to measure cortisol levels. Our results showed subjects treated with chronic OXT had a reduction in long call and peep vocalizations compared to subjects treated with chronic SAL. Subjects treated with chronic SAL and acute OXT produced more peeps and long calls compared to animals treated with acute SAL; however, patterns in this response depended on sex. Cortisol and locomotion were significantly higher during the Brief Separation period compared to the Non-Separation period; however, we did not find any treatment or sex effects. We conclude that chronic IN OXT given during development blunts the separation response, while acute OXT in chronic SAL subjects had sexually dimorphic effects, which could reflect increased partner seeking behaviors in males and increased anxiety in females.

A short note on oxytocin and stress attenuation

Stress is integral part of life and it initiates appropriate response at times of adversities to promise survival. Stress could be either physiological or psychogenic. Stress is often psychogenic in nature and it induces the release of cortisol from adrenal cortex into circulation by activating Hypo thalamo-pituitary-adrenal axis (HPA). Cortisol thus released mediates the stress response by its catabolic effects to enhance the activity of vital organs during emergency. However, prolonged activation of the HPA axis can lead to physical and mental illness as an outcome of persistent stress. Nature has bestowed the biological system with an array of endogenous mechanisms to buffer stress. Oxytocin, a nano-peptide released by the magno-cellular neurons of hypothalamic paraventricular nucleus (PVN) is an efficient stress buffering neuro-peptide. This hormone mediates many physiological and behavioural functions get released during stress. It attenuates the stress axis initiated by the release of corticotropin releasing hormone (CRH) from the parvocellular neurons of the same hypothalamic nucleus. Oxytocin released by PVN exerts an inhibitory effect on the release of CRH by down-regulating the expression of the gene that transcribes for this hypothalamic hormone. Thus, it inhibits the release of adreno cotico trophic hormone (ACTH) and cortisol, exerting an overall suppressive modulation of the stress axis and attenuates stress.

The role of sex-differentiated variations in stress hormones, antioxidants, and neuroimmune responses in relation to social interaction impairment in a rodent model of autism

Males are more likely to develop autism as a neurodevelopmental disorder than females, but the mechanisms underlying male susceptibility are not fully understood. In this paper, we used a well-characterized propionic acid (PPA) rodent model of autism to study sex differences in stress hormones, antioxidants' status, and the neuroimmune response that may contribute to the preponderance of autism in males. Sprague Dawley rats of both sexes were divided into a saline-treated group as controls and PPA-treated groups, receiving 250 mg/kg of PPA per day for three days. Animals' social behavior was examined using the three-chamber social test. Hormones (ACTH, corticosterone, melatonin, and oxytocin), oxidative stress biomarkers (glutathione, glutathione-S-transferase, and ascorbic acid), and cytokines (IL-6, IL-1α, IL-10, and IFNγ) were measured in the brain tissue of all the animals. The results showed a sex dimorphic social response to PPA treatment, where males were more susceptible to the PPA treatment and exhibited a significant reduction in social behavior with no effects observed in females. Also, sex differences were observed in the levels of hormones, antioxidants, and cytokines. Female rats showed significantly higher corticosterone and lower oxytocin, antioxidants, and cytokine levels than males. The PPA treatment later modulated these baseline differences. Our study indicates that the behavioral manifestation of autism in PPA-treated males and not females could be linked to neural biochemical differences between the sexes at baseline, which might play a protective role in females. Our results can contribute to early intervention strategies and treatments used to control autism, an increasingly prevalent disorder.

Post Orgasmic Illness Syndrome (POIS) and Delayed Onset Muscle Soreness (DOMS): Do They Have Anything in Common?

Post orgasmic illness syndrome is a rare, mysterious condition with an unknown pathomechanism and uncertain treatment. The symptoms of post orgasmic illness syndrome last about 2–7 days after an ejaculation. The current hypothesis proposes that the primary injury in post orgasmic illness syndrome is an acute compression proprioceptive axonopathy in the muscle spindle, as is suspected in delayed onset muscle soreness. The terminal arbor degeneration-like lesion of delayed onset muscle soreness is theorized to be an acute stress response energy-depleted dysfunctional mitochondria-induced impairment of Piezo2 channels and glutamate vesicular release. The recurring symptoms of post orgasmic illness syndrome after each ejaculation are suggested to be analogous to the repeated bout effect of delayed onset muscle soreness. However, there are differences in the pathomechanism, mostly attributed to the extent of secondary tissue damage and to the extent of spermidine depletion. The spermidine depletion-induced differences are as follows: modulation of the acute stress response, flu-like symptoms, opioid-like withdrawal and enhanced deregulation of the autonomic nervous system. The longitudinal dimension of delayed onset muscle soreness, in the form of post orgasmic illness syndrome and the repeated bout effect, have cognitive and memory consequences, since the primary injury is learning and memory-related.

Hormonal Differences in Intimate Partner Violence Perpetrators When They Cope with Acute Stress: A Pilot Study

BACKGROUND

Only a few studies have paid attention to the ability of perpetrators of intimate partner violence (IPVAW) against women to cope with acute stress, including hormonal parameters. In fact, previous studies assessed how salivary testosterone (Tsal) and cortisol (Csal) changed after coping with an acute emotional stressor (directly related to IPVAW), and they concluded that an imbalance between the two hormones might be characteristic of these men. Nevertheless, they neglected to examine the role of other hormones, such as salivary oxytocin (OXsal), which also seemed to play an important role in behavioral regulation, and whether this response could be generalized to other types of stress not directly related to IPVAW.

METHODS

This study aims to assess whether IPVAW perpetrators (n = 19) present differential hormonal (Tsal, Csal, OXsal and their ratios) and psychological state (anxiety, anger, and general affect) responses when coping with an acute cognitive laboratory stressor (a set of neuropsychological tests performed in front of an expert committee) in comparison with non-violent men (n = 16). This quasi-experimental study also assessed whether the psychological state variables drive this different hormonal response.

RESULTS

Our results revealed that IPVAW perpetrators had lower Csal and higher Tsal/Csal ratio levels during the post-task period, as well as higher total levels (average) of OXsal than controls. We also found that, only in IPVAW perpetrators, high levels of baseline anxiety and negative affect were related to high rises in Csal during the stress task.

CONCLUSIONS

These data present a background showing that IPVAW perpetrators and non-violent men cope differently with stress. These findings might help to identify idiosyncratic profiles of IPVAW perpetrators that can then be employed to establish their therapeutic needs. Moreover, we reinforced the importance of combining biological markers with self-reports, thus increasing the reliability of these forensic assessments.

Intranasal oxytocin compensates for estrus cycle-specific reduction of conditioned safety memory in rats: Implications for psychiatric disorders

Stress and anxiety disorder patients frequently fail to benefit from psychotherapies which often consist of inhibitory fear learning paradigms. One option to improve the therapy outcome is medication-enhanced psychotherapy. Research in humans and laboratory rodents has demonstrated that oxytocin (OT) reduces fear and facilitates fear extinction. However, the role of OT in conditioned safety learning, an understudied but highly suitable type of inhibitory fear learning, remains to be investigated. The present study aimed at investigating the effect of intranasal OT on conditioned safety. To test this, Sprague Dawley rats (♂n = 57; ♀n = 72) were safety conditioned. The effects of pre-training or pre-testing intranasal OT on conditioned safety and contextual fear, both measured by the acoustic startle response, and on corticosterone plasma levels were assessed. Furthermore, the involvement of the estrous cycle was analyzed. The present data show that intranasal OT administration before the acquisition or recall sessions enhanced conditioned safety memory in female rats while OT had no effects in male rats. Further analysis of the estrus cycle revealed that vehicle-treated female rats in the metestrus showed reduced safety memory which was compensated by OT-treatment. Moreover, all vehicle-treated rats, regardless of sex, expressed robust contextual fear following conditioning. Intranasal OT-treated rats showed a decrease in contextual fear, along with reduced plasma corticosterone levels. The present data demonstrate that intranasal OT has the capacity to compensate deficits in safety learning, along with a reduction in contextual fear and corticosterone levels. Therefore, add-on treatment with intranasal OT could optimize the therapy of anxiety disorders.

Gender Differences in the Relationship Between Financial Stress and Metabolic Abnormalities

BACKGROUND

Financial stress is associated with higher prevalence of metabolic abnormalities and cardiovascular disease, but the extent to which this association differs by type of metabolic abnormalities or gender is unclear.

OBJECTIVES

The study aims were (a) to examine the association between financial stress and the prevalence of common metabolic abnormalities and (b) to test the association for gender differences.

METHODS

A cross-sectional secondary analysis was conducted using data from the Retirement and Sleep Trajectories study, an ancillary study of the Wisconsin Sleep Cohort study. Composite indicator structural equation alpha modeling with a stacking approach was applied in the data analysis.

RESULTS

After controlling for covariates, financial stress was positively associated with the prevalence of abdominal obesity, metabolic syndrome, and dyslipidemia, with significant gender differences. Among men, financial stress was positively associated with the prevalence of hypertriglyceridemia. Among women, financial stress was positively associated with the prevalence of prediabetes, abdominal obesity, metabolic syndrome, and dyslipidemia.

CONCLUSION

Men living with financial stress are more likely to have hypertriglyceridemia, a specific metabolic abnormality and risk factor for acute cardiovascular events. However, financial stress in women is associated with a broader array of metabolic abnormalities (e.g., dyslipidemia, prediabetes, abdominal obesity, metabolic syndrome), highlighting a potential risk of multiple chronic conditions later in life.

Oxytocin Differentially Modulates Amygdala Responses during Top-Down and Bottom-Up Aversive Anticipation

The ability to successfully regulate negative emotions such as fear and anxiety is vital for mental health. Intranasal administration of the neuropeptide oxytocin (OXT) has been shown to reduce amygdala activity but to increase amygdala-prefrontal cortex connectivity during exposure to threatening stimuli suggesting that it may act as an important modulator of emotion regulation. The present randomized, between-subject, placebo-controlled pharmacological study combines the intranasal administration of OXT with functional magnetic resonance imaging (fMRI) during an explicit emotion regulation paradigm in 65 healthy male participants to investigate the modulatory effects of OXT on both bottom-up and top-down emotion regulation. OXT attenuates the activation in the posterior insular cortex and amygdala during anticipation of top-down regulation of predictable threat stimuli in participants with high trait anxiety. In contrast, OXT enhances amygdala activity during the bottom-up anticipation of unpredictable threat stimuli in participants with low trait anxiety. OXT may facilitate top-down goal-directed attention by attenuating amygdala activity in high anxiety individuals, while promoting bottom-up attention/vigilance to unexpected threats by enhancing amygdala activity in low anxiety individuals. OXT may thus have the potential to promote an adaptive balance between bottom-up and top-down attention systems depending on an individual's trait anxiety level.

Selective sub-nucleus effects of intra-amygdala oxytocin on fear extinction

There is growing evidence that the neuropeptide oxytocin (OT) modulates fear and extinction in humans and rodents through actions in corticolimbic circuits including the central amygdala (CeA). Prior studies have, however, been limited to subjects that exhibit intact basal extinction, rather than extinction-impaired populations that could potentially therapeutically benefit from viable OT-targeting treatments. Here, we assessed the effects of pre-extinction training infusion of OT into the CeA, or basolateral amygdala (BLA), on extinction in an inbred mouse strain (S1) model of impaired extinction. We found that intra-CeA OT, at a dose of 0.01 μg, enabled extinction memory formation, as evidenced by lesser freezing as compared to vehicle-infused controls on a drug-free retrieval test. Conversely, infusion of a higher, 1.0 μg OT dose, markedly reduced freezing and increased grooming during extinction training and produced elevated freezing on drug-free retrieval. Infusion of the 0.01 μg dose into the BLA was without behavioral effects. Together, our data show that OT acts in a dose-dependent manner within the CeA to promote extinction in otherwise extinction-deficient mice. These findings provide further support for the potential utility of OT as an adjunctive treatment to extinction-based therapies for trauma and anxiety disorders.

The effect of oxytocin, gender, and ovarian hormones on stress reactivity in individuals with cocaine use disorder

RATIONALE

Cocaine use disorder (CUD) is associated with dysregulation of the hypothalamic-pituitary-adrenal axis, which plays a critical role in the human stress response. Men and women with CUD differ in reactivity to social stressors. The hypothalamic neuropeptide oxytocin is involved in anxiolytic and natural reward processes, and has shown therapeutic potential for addictive disorders and stress reduction.

OBJECTIVES

To examine the impact of oxytocin (oxytocin (OXY) vs. placebo (PBO)) and gender (female (F) vs. male (M)) on response to a social stress task in individuals with CUD. To explore whether ovarian hormones moderate this stress response.

METHODS

One hundred twelve adults with CUD were randomized to receive 40 IU intranasal oxytocin (n = 56) or matching placebo (n = 56). Forty minutes after drug administration, participants were exposed to a social stressor. Generalized linear mixed models were used to examine neuroendocrine (cortisol) and subjective (craving, stress) response at pre-stressor, stressor + 0, + 10, + 30, + 60 min.

RESULTS

Gender moderated the effect of oxytocin on neuroendocrine response (p = 0.048); women receiving oxytocin (F + OXY) showed blunted cortisol response compared to the other three groups (F + PBO; M + OXY; M + PBO). There was a main effect of gender on subjective stress response; women reported greater stress following the stressor compared to men (p = 0.016). Oxytocin had no significant effect on craving or stress, and gender did not moderate the effect of oxytocin on either measure. Higher endogenous progesterone was associated with lower craving response in women (p = 0.033).

CONCLUSIONS

Oxytocin may have differential effects in men and women with CUD. Women may be at greater risk for relapse in response to social stressors, but ovarian hormones may attenuate this effect.

Effects of oxytocin administration on salivary sex hormone levels in autistic and neurotypical women

Background

Oxytocin administration, which may be of therapeutic value for individuals with social difficulties, is likely to affect endogenous levels of other socially relevant hormones. However, to date, the effects of oxytocin administration on endogenous hormones have only been examined in neurotypical individuals. The need to consider multi-hormone interactions is particularly warranted in oxytocin trials for autism due to evidence of irregularities in both oxytocin and sex steroid systems.

Methods

In this double-blind cross-over study, saliva samples were collected from 16 autistic and 29 neurotypical women before and after intranasal administration of 24 IU oxytocin or placebo. Oestradiol, testosterone, and oxytocin levels were quantified in saliva samples. Participants also completed the Autism-Spectrum Quotient (AQ) and Empathy Quotient (EQ) questionnaires.

Results

Distinct patterns of change in testosterone and oestradiol levels pre- to-post-administration were observed in autistic relative to neurotypical women (ANCOVA, p < 0.05 main effect of Group), controlling for sample collection time. The mean percent change oestradiol was + 8.8% for the autism group and − 13.0% for the neurotypical group (t = 1.81, p = 0.08), while the mean percent change testosterone was + 1.1% in the autism group and − 12.6% in the neurotypical group (t = 1.26, p = 0.22). In the oxytocin condition, the mean percent change oestradiol was + 12.6% in the autism group and − 6.9% in the neurotypical group (t = 1.78, p = 0.08), while the mean percent change testosterone was + 14.4% in the autism group and − 15.2% in the neurotypical group (t = 3.00, p = 0.006). Robust regression confirmed that group differences in percent change hormone levels were not driven by a small number of influential individuals. Baseline hormone levels did not differ between groups when considered individually. However, baseline testosterone relative to oestradiol (T:E2 ratio) was higher in autistic women (p = 0.023, Cohen’s d = 0.63), and this ratio correlated positively and negatively with AQ and EQ scores, respectively, in the combined sample.

Limitations

Further studies with larger and more diverse autistic sample are warranted to confirm these effects.

Conclusions

This study provides the first evidence that oxytocin influences endogenous testosterone levels in autistic individuals, with autistic women showing increases similar to previous reports of neurotypical men. These findings highlight the need to consider sex steroid hormones as a variable in future oxytocin trials.

A novel theory on the predictive value of variation in the β-endorphin system on the risk and severity of PTSD

Despite growing interest in genetic and psychosocial indicators of heightened susceptibility to posttraumatic stress disorder (PTSD), a predictive model, which explains why some individuals develop PTSD in response to life-threatening traumatic events, while others, when faced with the same or similar experiences, do not, has thus far remained out of reach. In this paper, we review the literature on gene-environment interactions in β-endorphin system functioning with regard to PTSD and suggest that variation, both genetic and with regard to environmental stimuli, in systems which, like the β-endorphin system, distort human perception of life-threatening traumatic experiences may account for some of the variance in resilience to the disorder. Given the role of β-endorphin in both social connections and physical exercise, this becomes especially relevant with regard to military selection, training, and leadership processes.

Alteration in oxytocin levels induced by early social environment affects maternal behavior and estrogen receptor alpha in mandarin voles (Microtus mandarinus)

Many studies have shown that the early social environment exerts long-term effects on the brain and also the parental behavior of adults. Oxytocin (OXT) is one of the most important neurotransmitters that regulate social behavior; howerve, whether the early social environment affects parental behavior via OXT remains unclear. Using socially monogamous adult mandarin voles (Microtus mandarinus), the present study found that 1) both paternal deprivation and early social deprivation significantly decreased OXT expression in both the paraventricular hypothalamic nucleus (PVN) and the supraoptic nucleus (SON) of F2 generation offspring; 2) systemic neonatal OXT injection in naïve animals promoted maternal but not paternal behavior in adult F2 offspring; 3) systemic neonatal OXT injection significantly increased ERα expression in both the medial preoptic area (MPOA) and the ventro medial hypothalamic nucleus (VMH) in female but not in male mandarin voles; 4) systemic neonatal administration of an OXT antagonist significantly reduced ERα expression in the bed nucleus of the stria terminalis (BNST), VMH, and the arcuate hypothalamic nucleus (Arc) in females and in all examined brain regions in males. In summary, the obtained data demonstrate that the early social environment could affect OXT level, which in turn leads to long-term effects on ERα expression in relevant brain regions, consequently affecting maternal behavior but not paternal behavior.