Oxytocin: From milk ejection to maladaptation in stress response and psychiatric disorders. A psychoneuroendocrine perspective

Sex matters: The impact of oxytocin on healthy conditions and psychiatric disorders

Oxytocin (OT) is involved in the regulation of physiological processes and emotional states, with increasing evidence for its beneficial actions being mediated by the autonomic and immune systems. Growing evidence suggests that OT plays a role in the pathophysiology of different psychiatric disorders. Given the limited information in humans the aim of this study was to retrospectively explore plasma OT levels in psychiatric patients, particularly focusing on sex-related differences, as compared with healthy controls. The patients studied here were divided into three groups diagnosed with obsessive-compulsive disorder (OCD), post-traumatic stress disorder (PTSD) or major depressive disorder (MDD). Plasma OT levels were significantly different between healthy men and women, with the latter showing higher values, while none of the three psychiatric groups showed sex-related differences in the parameters measured here. The intergroup analyses showed that the OT levels were significantly higher in OCD, lower in PTSD and even more reduced in MDD patients than in healthy subjects. These differences were also confirmed when gender was considered, with the exception of PTSD men, in whom OT levels were similar to those of healthy men. The present results indicated that OT levels were higher amongst healthy women than men, while a sex difference was less apparent or reversed in psychiatric patients. Reductions in sex differences in psychopathologies may be related to differential vulnerabilities in processes associated with basic adaptive and social functions.

Different oxytocin and corticotropin-releasing hormone system changes in bipolar disorder and major depressive disorder patients

Background

Oxytocin (OXT) and corticotropin-releasing hormone (CRH) are both produced in hypothalamic paraventricular nucleus (PVN). Central CRH may cause depression-like symptoms, while peripheral higher OXT plasma levels were proposed to be a trait marker for bipolar disorder (BD). We aimed to investigate differential OXT and CRH expression in the PVN and their receptors in prefrontal cortex of major depressive disorder (MDD) and BD patients. In addition, we investigated mood-related changes by stimulating PVN-OXT in mice.

Methods

Quantitative immunocytochemistry and in situ hybridization were performed in the PVN for OXT and CRH on 6 BD and 6 BD-controls, 9 MDD and 9 MDD-controls. mRNA expressions of their receptors (OXTR, CRHR1 and CRHR2) were determined in anterior cingulate cortex and dorsolateral prefrontal cortex (DLPFC) of 30 BD and 34 BD-controls, and 24 MDD and 12 MDD-controls. PVN of 41 OXT-cre mice was short- or long-term activated by chemogenetics, and mood-related behavior was compared with 26 controls.

Findings

Significantly increased OXT-immunoreactivity (ir), OXT-mRNA in PVN and increased OXTR-mRNA in DLPFC, together with increased ratios of OXT-ir/CRH-ir and OXTR-mRNA/CRHR-mRNA were observed in BD, at least in male BD patients, but not in MDD patients. PVN-OXT stimulation induced depression-like behaviors in male mice, and mixed depression/mania-like behaviors in female mice in a time-dependent way.

Interpretation

Increased PVN-OXT and DLPFC-OXTR expression are characteristic for BD, at least for male BD patients. Stimulation of PVN-OXT neurons induced mood changes in mice, in a pattern different from BD.

Funding

10.13039/501100001809National Natural Science Foundation of China (81971268, 82101592).

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.

Beta-Endorphin and Oxytocin in Patients with Alcohol Use Disorder and Comorbid Depression

Background: The neuropeptides β-endorphin and oxytocin are released into the bloodstream as hormones from the pituitary gland but also have an important function as neuroregulators in the forebrain. The blood levels of both polypeptides have been shown to reflect depressive symptoms. β-Endorphin, in particular, is also involved in abstinence from alcohol. Methods: The serum levels of β-endorphin and oxytocin were measured during the early withdrawal phase in patients with alcohol use disorder (AUD) with (N = 35) or without (N = 45) depressive comorbidity and compared with those in healthy volunteers (N = 23). In addition to comparing the groups, the study examined whether serum levels correlated with various psychometric measures of dependence, depression and aggression, as well as with clinical characteristics of dependence. Results: Both serum levels of beta-endorphin and oxytocin were significantly lower in patients than those in healthy controls (p = 0.011 for β-endorphin and p = 0.005 for oxytocin, Kruskal–Wallis test). In patients with depressive comorbidity, the significance was greatest (p = 0.005 for β-endorphin and p = 0.004 for oxytocin, U-test). There was no correlation with clinical or psychometric parameters (p > 0.05, Spearman test), but beta-endorphin levels did correlate significantly with physical aggression (p = 0.026, Spearman test). Conclusions: Serum levels of β-endorphin and oxytocin are lower in patients with AUD, particularly in those with depressive comorbidity. β-Endorphin levels correlated with physical aggression according to the Buss–Durkee (BDHI) estimates.

Oxytocin: at birth and beyond. A systematic review of the long-term effects of peripartum oxytocin

Oxytocin is one of the most commonly used medications during labour and delivery. Recent insights from basic neuroscience research suggest that the uterotonic effects of oxytocin may arguably be trivial when compared with its profound effects on higher-order human behaviour. The purpose of this review is to highlight the potential consequences of manipulating oxytocinergic signalling during the peripartum period and its long-term impact on the maternal-infant dyad. We identified four domains where modulation of oxytocinergic signalling might be consequential: postpartum depression; breastfeeding; neurodevelopment; and chronic pain, and performed a literature search to address the impact of peripartum oxytocin administration. We have shown modest, but inconsistent, evidence linking peripartum oxytocin administration with postpartum depression. Breastfeeding success appeared to be negatively correlated with peripartum oxytocin exposure, perhaps secondary to impaired primitive neonatal reflexes and maternal-infant bonding. The association between perinatal oxytocin exposure and subsequent development of neurodevelopmental disorders such as autism in the offspring was weak, but these studies were limited by the lack of information on the cumulative dose. Finally, we identified substantial evidence for analgesic and anti-hypersensitivity effects of oxytocin which might partly explain the low incidence of chronic pain after caesarean birth. Although most data presented here are observational, our review points to a compelling need for robust clinical studies to better dissect the impact of peripartum oxytocin administration, and as stewards of its use, increase the precision with which we administer oxytocin to prevent overuse of the drug.

Increased oxytocin levels among abstinent heroin addicts: Association with aggressiveness, psychiatric symptoms and perceived childhood neglect

A disruption of the oxytocin system seems to affect a variety of brain functions including emotions, mood and social behavior possibly underlying severe social deficits and susceptibility for substance use and mental health disorders. Early life adversity, such as insecure attachment in childhood, has been suggested to influence oxytocin tone contributing to a condition of neurobiological vulnerability. Aim of the present study was to investigate oxytocin serum levels in abstinent heroin addicted patients, in comparison with healthy controls, and the possible correlation with co-occurring psychiatric symptoms, aggressiveness and perception of parental neglect. Eighteen (18) abstinent patients, affected by heroin use disorders, and 18 control subjects, who never used drugs or abused alcohol, were included in the study and submitted to 1) collection of a blood sample for oxytocin assay, 2) Symptoms Check List 90 for psychiatric symptoms evaluation 3) Buss Durkee Hostility Inventory to measure aggressiveness 4) Child Experience of Care and Abuse-Questionnaire to retrospectively test the perception of parental neglect. Heroin exposure extent and heroin dosages were also recorded. Oxytocin serum levels were unexpectedly significantly higher among abstinent patients affected by heroin use disorders and positively correlated with psychiatric symptoms, aggressiveness and mother neglect scores. No correlation was evidenced between oxytocin and heroin exposure extent or dosages. Our findings appear to contradict the simplistic view of oxytocin as a pro-social hormone and confirm previous evidence concerning the peptide levels direct association with aggressive behavior and mood disorders. Considering a more complex mechanism, oxytocin would increase the sensitivity to social salience cues related to contextual or inter-individual factors, promoting pro-sociality in "safe" conditions and, in contrast, inducing more defensive and "anti-social" emotions and behaviors when the social cues are interpreted as "unsafe". This latter condition is often characterizing the clinical history of addicted patients.

Oxytocin and Anxiety Disorders

In the present chapter, we review the literature focusing on oxytocin (OT)-centered research in anxiety spectrum conditions, comprising separation anxiety disorder, specific phobias, social anxiety disorder (SAD), panic disorder, generalized anxiety disorder, and anxiety-related endophenotypes (e.g., trust behavior, behavioral inhibition, neuroticism, and state/trait anxiety). OT receptor gene (OXTR) polymorphisms have been implicated in gene-environment interactions with attachment style and childhood maltreatment and to influence clinical outcomes, including SAD intensity and limbic responsiveness. Epigenetic OXTR DNA methylation patterns have emerged as a link between categorical, dimensional, neuroendocrinological, and neuroimaging SAD correlates, highlighting them as potential peripheral surrogates of the central oxytocinergic tone. A pathophysiological framework of OT integrating the dynamic nature of epigenetic biomarkers and the summarized genetic and peripheral evidence is proposed. Finally, we emphasize opportunities and challenges of OT as a key network node of social interaction and fear learning in social contexts. In conjunction with multi-level investigations incorporating a dimensional understanding of social affiliation and avoidance in anxiety spectrum disorders, these concepts will help to promote research for diagnostic, state, and treatment response biomarkers of the OT system, advancing towards indicated preventive interventions and personalized treatment approaches.

The steroid metabolome in men with mood and anxiety disorders

The mood and behavior of individuals result from an orchestra of many factors. Among them steroids play an important role; however, only several common hormones have been investigated in this respect. It has been demonstrated that some steroid metabolites long considered merely the products of steroid hormone metabolism in fact possess considerable activity in the CNS. For this reason we studied the steroid metabolome including 50 analytes in 20 men with depression, 20 men with anxiety and 30 healthy controls. Significant differences were found not only between controls and men with either depression or anxiety, but also between men with depression and anxiety. Particularly striking were those steroids until now not generally associated with depression or anxiety, namely conjugated steroid forms, especially sulfates.

Plasma Oxytocin Levels in Untreated Adult Obsessive-Compulsive Disorder Patients

BACKGROUND AND AIM

Given the paucity of information on the possible role of oxytocin (OT) in the pathophysiology of obsessive-compulsive disorder (OCD), our study aimed at evaluating plasma OT levels in a group of 44 OCD outpatients, as compared with a similar group of healthy control subjects. At the same time, the relationships between OT and clinical features and romantic attachment characteristics were examined as well.

METHODS

Diagnosis was assessed according to DSM-IV-TR criteria, while the OCD severity was measured by means of the Y-BOCS rating scale. All patients were drug free and not depressed. The romantic attachment was assessed by means of the Italian version of the 'Experiences in Close Relationships' questionnaire. Plasma OT levels were evaluated by means of a standard RIA kit.

RESULTS

The main findings of our study showed that OT levels were increased in OCD patients, as compared with healthy subjects, and negatively related to symptom severity. Positive relationships were detected between OT levels and the fearful-avoidant and dismissing styles of romantic attachments, but only in male OCD patients.

CONCLUSION

Taken together, these findings suggest that OT may play a role in OCD pathophysiology and also in the romantic attachment of patients with gender specificity.

Hypnosis, attachment, and oxytocin:an integrative perspective (1.)

This article considers links between clinical hypnosis, attachment theory, and oxytocin. First, it proposes that commonalities between clinical hypnosis and attachment theory may improve our understanding of the hypnotherapeutic process. Then, it suggests that an integrative model unifying clinical hypnosis and attachment theory may constitute a link between clinical hypnosis and a neurobiological factor such as oxytocin. Finally, it discusses the implications of these hypotheses for clinical practice and future researches.

Novel oxytocin gene expression in the hindbrain is induced by alcohol exposure: transgenic zebrafish enable visualization of sensitive neurons

BACKGROUND

Fetal Alcohol Spectrum Disorders (FASD) are a collection of disorders resulting from fetal ethanol exposure, which causes a wide range of physical, neurological and behavioral deficits including heightened susceptibility for alcoholism and addictive disorders. While a number of mechanisms have been proposed for how ethanol exposure disrupts brain development, with selective groups of neurons undergoing reduced proliferation, dysfunction and death, the induction of a new neurotransmitter phenotype by ethanol exposure has not yet been reported.

PRINCIPAL FINDINGS

The effects of embryonic and larval ethanol exposure on brain development were visually monitored using transgenic zebrafish expressing cell-specific green fluorescent protein (GFP) marker genes. Specific subsets of GFP-expressing neurons were highly sensitive to ethanol exposure, but only during defined developmental windows. In the med12 mutant, which affects the Mediator co-activator complex component Med12, exposure to lower concentrations of ethanol was sufficient to reduce GFP expression in transgenic embryos. In transgenic embryos and larva containing GFP driven by an oxytocin-like (oxtl) promoter, ethanol exposure dramatically up-regulated GFP expression in a small group of hindbrain neurons, while having no effect on expression in the neuroendocrine preoptic area.

CONCLUSIONS

Alcohol exposure during limited embryonic periods impedes the development of specific, identifiable groups of neurons, and the med12 mutation sensitizes these neurons to the deleterious effects of ethanol. In contrast, ethanol exposure induces oxtl expression in the hindbrain, a finding with profound implications for understanding alcoholism and other addictive disorders.

A link between oxytocin and serotonin in humans: supporting evidence from peripheral markers

Pharmacological studies indicate a functional interaction between the serotonergic and oxytocinergic systems. In particular, some selective serotonin (5-HT) reuptake inhibitors, such as citalopram and fluvoxamine, seem to exert part of their antidepressant effects through oxytocin (OT) release. Further, the administration of fenfluramine, a serotonergic agonist, to healthy subjects increases plasma OT levels. Interestingly, immunocytochemical and double-immunofluorescent techniques revealed a high degree of overlap between 5-HT transporter (SERT)-labeled fibers and OT-containing cells in the paraventricular and supraoptic nuclei of primate hypothalamus. These findings suggest that the influence of 5-HT on OT system might be mediated by SERT. In this study, we explored the possible existence of a link between OT and SERT in human subjects, by means of two peripheral markers, the platelet SERT, as measured by [³H]-paroxetine ([³H]-Par) binding, and plasma OT levels. As far as [³H]-Par binding parameters are concerned, the Bmax (mean ± SD, fmol/mg protein) was 1155 + 130 and the Kd (mean ± SD, nM) was 1.31 ± 0.61. The OT plasma levels (mean ± SD, pg/ml) were 1.14 ± 1.07. A significant and positive correlation was found between plasma OT levels and Kd values (correlation coefficient: r: 0.466, p = .038). This result represents the first evidence of an interaction between OT and SERT, as measured by [³H]-Par binding, at peripheral levels in humans. Given the several activities mediated by both OT and 5-HT, such a relationship might provide new perspectives and insights into psychiatric disorders and/or social relationship disturbances, as well as novel treatment strategies overcoming and/or integrating the serotonergic paradigm.

Reconsidering GHB: orphan drug or new model antidepressant?

For six decades, the principal mode of action of antidepressant drugs is the inhibition of monoamine re-uptake from the synaptic cleft. Tricyclic antidepressants, selective serotonin re-uptake inhibitors (SSRIs) and the new generation of dual antidepressants all exert their antidepressant effects by this mechanism. In the early days of the monoaminergic era, other efforts have been made to ameliorate the symptoms of depression by pharmacological means. The gamma-aminobutyric acid (GABA) system was and possibly still is one of the main alternative drug targets. Gammahydroxybutyrate (GHB) was developed as an orally active GABA analogue. It was tested in animal models of depression and human studies. The effects on sleep, agitation, anhedonia and depression were promising. However, the rise of benzodiazepines and tricyclic antidepressants brought GHB out of the scope of possible treatment alternatives. GHB is a GABA(B) and GHB receptor agonist with a unique spectrum of behavioural, neuroendocrine and sleep effects, and improves daytime sleepiness in various disorders such as narcolepsy, Parkinson's disease and fibromyalgia. Although it was banned from the US market at the end of the 1990s because of its abuse and overdose potential, it later was approved for the treatment of narcolepsy. New research methods and an extended view on other neurotransmitter systems as possible treatment targets of antidepressant treatment brought GHB back to the scene. This article discusses the unique neurobiological effects of GHB, its misuse potential and possible role as a model substance for the development of novel pharmacological treatment strategies in depressive disorders.

The influence of depressive symptomatology and perceived stress on plasma and salivary oxytocin before, during and after a support enhancement intervention

Oxytocin (OT) activity increases in response to stress as well as to warm social contact. Subclinical depression is associated with higher stress but less reward from social contacts. The present investigation was intended to examine whether husbands and wives with high depressive symptomatology scores have increased plasma and salivary OT that may be mediated partly by higher perceived stress, and also to assess whether an intervention to convey partner support through "warm touch" may reduce effects of depressive symptoms on OT. In this study, 34 healthy married couples (n=68) ages 20-39 provided self reports of depressive symptoms (CESD) and stress (Perceived Stress Scale) before being randomly assigned to a 4-week intervention study enhancing partner support through "warm touch", or to a "behavior monitoring" control group. Plasma oxytocin levels were obtained pre- and post-intervention, while salivary oxytocin was taken at home during week 1 and week 4. Results revealed that subjects with higher depressive symptoms scores had higher plasma OT levels at pre-intervention, and higher salivary OT levels at home during week 1 (p<.05). Plasma OT results were moderated by gender such that plasma OT levels were highest among females high in depressive symptomology. Higher perceived stress was also linked to both higher depressive symptomatology (r=+65, p<.0001) and plasma OT (p< .05) and a significant mediator. During the intervention, salivary OT remained elevated among subjects high in depressive symptomatology in the control group but not the intervention group. At post-intervention, plasma OT levels in subjects with vs. without depressive symptomatology no longer differed. Results indicate that subclinical depression is associated with elevated plasma and salivary OT levels, which may be mediated in part by increased stress. OT differences linked to subclinical depression were minimized by the warm touch intervention.

Maternal stress affects postnatal growth and the pituitary expression of prolactin in mouse offspring

Maternal stress exerts long-lasting psychiatric and somatic on offspring, which persist into adulthood. However, the effect of maternal stress on the postnatal growth of pups has not been widely reported. In this study, we found that maternal immobilization stress (IS) during lactation resulted in low body weight of male mouse offspring, which persisted after weaning. Despite free access to chow, IS induced maternal malnutrition and decreased the serum insulin-like growth factor-1 (IGF-1) levels in the mothers and in the pups. mRNA expression analysis of anterior pituitary hormones in the pups revealed that growth hormone (GH) and prolactin (PRL), but no other hormones, were decreased by IS. Expression of the pituitary transcription factor PIT1 and isoforms of PITX2, which are essential for the development and function of GH-producing somatotropes and PRL-producing lactotropes, was decreased, whereas that of PROP1, which is critical for the earlier stages of pituitary development, was unchanged. Immunohistochemistry also showed a decrease in pituitary PRL protein expression. These results suggest that stress in a postpartum mother has persistent effects on the body weight of the offspring. Reduced PRL expression in the offspring's pituitary gland may play a role in these effects.