Plasma oxytocin distributions in a large cohort of women and men and their gender-specific associations with anxiety

Changes in social functioning and circulating oxytocin and vasopressin following the migration to a new country

Prior studies have reported associations between plasma oxytocin and vasopressin and markers of social functioning. However, because most human studies have used cross-sectional designs, it is unclear whether plasma oxytocin and vasopressin influences social functioning or whether social functioning modulates the production and peripheral release of these peptides. In order to address this question, we followed individuals who experienced major changes in social functioning subsequent to the migration to a new country. In this study, 59 new international students were recruited shortly after arrival in the host country and reassessed 2 and 5 months later. At each assessment participants provided information on their current social functioning and blood samples for oxytocin and vasopressin analysis. Results indicated that changes in social functioning were not related to changes in plasma oxytocin. Instead, baseline oxytocin predicted changes in social relationship satisfaction, social support, and loneliness over time. In contrast, plasma vasopressin changed as a function of social integration. Baseline vasopressin was not related to changes in social functioning over time. These results emphasize the different roles of plasma oxytocin and vasopressin in responses to changes in social functioning in humans.

Emotion and mood adaptations in the peripartum female:complementary contributions of GABA and oxytocin

Peripartum hormones and sensory cues from young modify the maternal brain in ways that can render females either at risk for, or resilient to, elevated anxiety and depression. The neurochemical systems underlying these aspects of maternal emotional and mood states include the inhibitory neurotransmitter GABA and the neuropeptide oxytocin (OXT). Data from laboratory rodents indicate that increased activity at the GABA(A) receptor contributes to the postpartum suppression of anxiety-related behaviour that is mediated by physical contact with offspring, whereas dysregulation in GABAergic signalling results in deficits in maternal care, as well as anxiety- and depression-like behaviours during the postpartum period. Similarly, activation of the brain OXT system accompanied by increased OXT release within numerous brain sites in response to reproductive stimuli also reduces postpartum anxiety- and depression-like behaviours. Studies of peripartum women are consistent with these findings in rodents. Given the similar consequences of elevated central GABA and OXT activity on maternal anxiety and depression, balanced and partly reciprocal interactions between these two systems may be essential for their effects on maternal emotional and mood states, in addition to other aspects of postpartum behaviour and physiology.

The role of oxytocin in mothers' theory of mind and interactive behavior during the perinatal period

The present longitudinal study examined the relations between plasma oxytocin, theory of mind, and maternal interactive behavior during the perinatal period. A community sample of women was assessed at 12-14 weeks gestation, 32-34 weeks gestation, and 7-9 weeks postpartum. Oxytocin during late pregnancy was significantly positively correlated with a measure of theory of mind, and predicted theory of mind ability after controlling for parity, maternal education, prenatal psychosocial risk, and general anxiety, measured during the first trimester. Theory of mind was associated with less remote and less depressive maternal interactive behavior. Oxytocin, across all time points, was not directly related to maternal interactive behavior. However, there was a significant indirect effect of oxytocin during late pregnancy on depressive maternal behavior via theory of mind ability. These preliminary findings suggest that changes in the oxytocinergic system during the perinatal period may contribute to the awareness of social cues, which in turn plays a role in maternal interactive behavior.

Separation anxiety, attachment and inter-personal representations: disentangling the role of oxytocin in the perinatal period

In this paper, we aimed to assess cross-sectionally and longitudinally associations between disturbances in maternal early attachment experiences, symptoms of separation anxiety and depression and oxytocin plasma levels. We examined a mediational model that tested the hypothesis that anxious attachment style arising from the mothers’ early bonding experiences with her own parents was associated with high levels of separation anxiety which, via its impact on depression, was associated with reduced levels of oxytocin in the postnatal period. Data is reported on a structured sample of 127 women recruited during pregnancy from a general hospital antenatal clinic and an initial follow up cohort of 57 women who were re-assessed at 3-months post-partum. We found an association between lower oxytocin level in the post partum period and symptoms of separation anxiety and depression during pregnancy, as well as maternal negative interpersonal representations, upbringing attributes and anxious attachment style. Further meditational analysis revealed that the unique association between anxious attachment and depression is mediated by separation anxiety and that depressed mood mediated the relationship between separation anxiety and oxytocin. In conjunction with evidence from the literature suggesting that lower oxytocin level is associated with bonding difficulties, our findings have significant implications for understanding the biological processes underpinning adverse attachment experiences, negative affect state, and mother-to-infant bonding difficulties.

CSF and blood oxytocin concentration changes following intranasal delivery in macaque

Oxytocin (OT) in the central nervous system (CNS) influences social cognition and behavior, making it a candidate for treating clinical disorders such as schizophrenia and autism. Intranasal administration has been proposed as a possible route of delivery to the CNS for molecules like OT. While intranasal administration of OT influences social cognition and behavior, it is not well established whether this is an effective means for delivering OT to CNS targets. We administered OT or its vehicle (saline) to 15 primates (Macaca mulatta), using either intranasal spray or a nebulizer, and measured OT concentration changes in the cerebral spinal fluid (CSF) and in blood. All subjects received both delivery methods and both drug conditions. Baseline samples of blood and CSF were taken immediately before drug administration. Blood was collected every 10 minutes after administration for 40 minutes and CSF was collected once post-delivery, at the 40 minutes time point. We found that intranasal administration of exogenous OT increased concentrations in both CSF and plasma compared to saline. Both delivery methods resulted in similar elevations of OT concentration in CSF, while the changes in plasma OT concentration were greater after nasal spray compared to nebulizer. In conclusion our study provides evidence that both nebulizer and nasal spray OT administration can elevate CSF OT levels.

Oxytocin plasma concentrations in children and adolescents with autism spectrum disorder: correlation with autistic symptomatology

Findings from research in animal models and humans have shown a clear role for the neuropeptide oxytocin (OT) on complex social behaviors. This is also true in the context of autism spectrum disorder (ASD). Previous studies on peripheral OT concentrations in children and young adults have reported conflicting results with the initial studies presenting mainly decreased OT plasma levels in ASD compared to healthy controls. Our study therefore aimed to further investigate changes in peripheral OT concentrations as a potential surrogate for the effects observed in the central nervous system (CNS) in ASD. OT plasma concentrations were assessed in 19 male children and adolescents with ASD, all with an IQ > 70 (age 10.7 ± 3.8 years), 17 healthy male children (age 13.6 ± 2.1 years) and 19 young male patients with attention deficit hyperactivity disorder (ADHD) as a clinical control group (age 10.4 ± 1.9 years) using a validated radioimmunoassay. Analysis of covariance revealed significant group differences in OT plasma concentrations (F(2, 48) = 9.574, p < 0.001, η2 = 0.285; plasma concentrations ASD 19.61 ± 7.12 pg/ml, ADHD 8.05 ± 5.49 pg/ml, healthy controls 14.43 ± 9.64 pg/ml). Post hoc analyses showed significantly higher concentrations in children with ASD compared to ADHD (p < 0.001). After Bonferroni correction, there was no significant difference in ASD in comparison with healthy controls (p = 0.132). A significant strong correlation between plasma OT and autistic symptomatology, assessed by the Autism Diagnostic Observation Schedule, was observed in the ASD group (p = 0.013, r = 0.603). Patients with ADHD differed from healthy control children by significantly decreased OT concentrations (p = 0.014). No significant influences of the covariates age, IQ, medication and comorbidity could be seen. Our preliminary results point to a correlation of OT plasma concentrations with autistic symptom load in children with ASD and a modulation of the OT system also in the etiologically and phenotypically overlapping disorder ADHD. Further studies in humans and animal models are warranted to clarify the complex association of the OT system with social impairments as well as stress-related and depressive behavior and whether peripheral findings reflect primary changes of OT synthesis and/or release in relevant areas of the CNS.

[Oxytocin: evidence for a therapeutic potential of the social neuromodulator]

Only few substances have achieved such a great prominence in recent years as the hypothalamic neuropeptide oxytocin, which is also widely known as the love hormone. Oxytocin is a potent neuromodulator which can improve social cognitive functions including empathy, trust, cooperation and social learning. However, oxytocin can also promote negative social behavior and increase poor memory and feelings of fear in social situations. Positive data from initial clinical trials give rise to the hope that oxytocin will prove to be a substance which is suitable for targeted treatment of poor social-cognitive behavior in neuropsychiatric diseases. This review article summarizes the most important recent preclinical and clinical human studies and discusses the findings presented with respect to current concepts of personal and contextual influences.

Psychosocial stress moderates the relationships between oxytocin, perinatal depression, and maternal behavior

The hormone oxytocin (OT) is of particular interest in the study of childbearing women, as it has a role in the onset and course of labor and breastfeeding. Recent research has linked OT to maternal caregiving behavior towards her infant, and to postpartum depressive symptomatology. There is also evidence that psychosocial adversity affects the oxytocin system. The present study investigated the relationship of endogenous OT in women during pregnancy and at 8weeks postpartum to psychosocial stress, maternal symptoms of depression, and maternal sensitive behavior. It was hypothesized that OT would mediate the effects of maternal depressive symptoms on maternal interactive behavior. We also tested the hypothesis that psychosocial stress would moderate the relationship between OT and maternal depressive symptoms and sensitive behavior. A community sample of 287 women was assessed at 12-14weeks of gestation, 32-34weeks of gestation, and 7-9weeks postpartum. We measured plasma OT, maternal symptoms of depression and psychosocial stress. At the postpartum home visit, maternal behavior in interaction with the infant was videotaped, and then coded to assess sensitivity. In the sample as a whole, OT was not related to maternal depressive symptoms or to sensitive maternal behavior. However, among women who reported high levels of psychosocial stress, higher levels of plasma OT were associated with fewer depressive symptoms and more sensitive maternal behavior. These results suggest that endogenous OT may act as a buffer against the deleterious effects of stress, thereby protecting high risk women from developing depressive symptoms and promoting more sensitive maternal interactive behavior.

Transgenerational effects of social stress on social behavior, corticosterone, oxytocin, and prolactin in rats

Social stressors such as depressed maternal care and family conflict are robust challenges which can have long-term physiological and behavioral effects on offspring and future generations. The current study investigates the transgenerational effects of an ethologically relevant chronic social stress on the behavior and endocrinology of juvenile and adult rats. Exposure to chronic social stress during lactation impairs maternal care in F0 lactating dams and the maternal care of the F1 offspring of those stressed F0 dams. The overall hypothesis was that the male and female F2 offspring of stressed F1 dams would display decreased social behavior as both juveniles and adults and that these behavioral effects would be accompanied by changes in plasma corticosterone, prolactin, and oxytocin. Both the female and male F2 offspring of dams exposed to chronic social stress displayed decreased social behavior as juveniles and adults, and these behavioral effects were accompanied by decreases in basal concentrations of corticosterone in both sexes, as well as elevated juvenile oxytocin and decreased adult prolactin in the female offspring. The data support the conclusion that social stress has transgenerational effects on the social behavior of the female and male offspring which are mediated by changes in the hypothalamic-pituitary-adrenal axis and hypothalamic-pituitary-gonadal axis. Social stress models are valuable resources in the study of the transgenerational effects of stress on the behavioral endocrinology of disorders such as depression, anxiety, autism, and other disorders involving disrupted social behavior.

Validation of an enzyme-linked immunoassay (ELISA) for plasma oxytocin in a novel mammal species reveals potential errors induced by sampling procedure

BACKGROUND

The neuropeptide oxytocin is increasingly the focus of many studies investigating human and animal social behaviours and diseases. However, interpretation and comparison of results is made difficult by a lack of consistent methodological approaches towards analysing this hormone.

NEW METHOD

This study determined the sample collection and analysis protocols that cause the least amounts of protocol dependant variation in plasma oxytocin concentrations detected by ELISA. The effect of vacutainer type, sample extraction prior to analysis and capture and restraint protocol were investigated while validating an assay protocol for two novel species, grey seals (Halichoerus grypus) and harbour seals (Phoca vitulina).

RESULTS

Where samples are extracted prior to analysis, vacutainer type (EDTA mean: 8.25±0.56 pg/ml, heparin mean: 8.25±0.62 pg/ml, p=0.82), time taken to obtain a sample and restraint protocol did not affect the concentration of oxytocin detected. However, concentrations of oxytocin detected in raw plasma samples were significantly higher than those in extracted samples, and varied significantly with vacutainer type (EDTA mean: 534.4±43.7 pg/ml, heparin mean: 300.9±19.6 pg/ml, p<0.001) and capture and restraint methodology. There was no relationship between oxytocin concentrations detected in raw and extracted plasma (p=0.25).

COMPARISON WITH EXISTING METHOD(S)

Over half the reviewed published studies analysing plasma oxytocin use raw plasma and different vacutainer types are used without consistency or justification through-out the literature.

CONCLUSIONS

We caution that studies using raw plasma are likely to over estimate oxytocin concentrations, cannot be used to accurately infer true values via correlations and are susceptible to variation according vacutainer type.

Oxytocin's role in anxiety: a critical appraisal

A growing literature suggests that the oxytocin (OT) system may play a role in human anxiety states, anxiety-related traits, and moreover, that this system may be a target for the development of novel anxiolytic treatments. However, studies of OT's acute and chronic effects on various aspects of anxiety have produced mixed results. In this forward-looking review, we discuss the myriad phenomena to which the term "anxiety" is applied in the OT literature and the problem this presents developing a coherent picture of OT's role in anxiety. We then survey several different fields of research that support the role of the OT system in human anxiety, including evolutionary perspectives, translational and neuroimaging research, genetic studies, and clinical trials of intranasal OT. As an outgrowth of this data, we propose a "bowtie" model of OT's role at the interface of social attachment and anxiety. We next direct attention to understudied brain regions and neural circuits which may be important to study in OT experiments in humans anxiety disorders. Finally, we conclude by proposing questions and priorities for studying both the clinical potential of OT in anxiety, as well as mechanisms that may underlie this potential. Crucially, these priorities include targeted proof-of-concept clinical trials of IN OT in certain anxiety disorders, including investigations of individual moderators of OT's anxiolytic effects (i.e. sex, genetic factors, and early experience). This article is part of a Special Issue entitled Oxytocin and Social Behav.

Oxytocin pathways and the evolution of human behavior

This review examines the hypothesis that oxytocin pathways--which include the neuropeptide oxytocin, the related peptide vasopressin, and their receptors--are at the center of physiological and genetic systems that permitted the evolution of the human nervous system and allowed the expression of contemporary human sociality. Unique actions of oxytocin, including the facilitation of birth, lactation, maternal behavior, genetic regulation of the growth of the neocortex, and the maintenance of the blood supply to the cortex, may have been necessary for encephalization. Peptide-facilitated attachment also allows the extended periods of nurture necessary for the emergence of human intellectual development. In general, oxytocin acts to allow the high levels of social sensitivity and attunement necessary for human sociality and for rearing a human child. Under optimal conditions oxytocin may create an emotional sense of safety. Oxytocin dynamically moderates the autonomic nervous system, and effects of oxytocin on vagal pathways, as well as the antioxidant and anti-inflammatory effects of this peptide, help to explain the pervasive adaptive consequences of social behavior for emotional and physical health.

Effects of selective serotonin reuptake inhibitor treatment on plasma oxytocin and cortisol in major depressive disorder

BACKGROUND

Oxytocin is known for its capacity to facilitate social bonding, reduce anxiety and for its actions on the stress hypothalamopituitary adrenal (HPA) axis. Since oxytocin can physiologically suppress activity of the HPA axis, clinical applications of this neuropeptide have been proposed in conditions where the function of the HPA axis is dysregulated. One such condition is major depressive disorder (MDD). Dysregulation of the HPA system is the most prominent endocrine change seen with MDD, and normalizing the HPA axis is one of the major targets of recent treatments. The potential clinical application of oxytocin in MDD requires improved understanding of its relationship to the symptoms and underlying pathophysiology of MDD. Previous research has investigated potential correlations between oxytocin and symptoms of MDD, including a link between oxytocin and treatment related symptom reduction. The outcomes of studies investigating whether antidepressive treatment (pharmacological and non-pharmacological) influences oxytocin concentrations in MDD, have produced conflicting outcomes. These outcomes suggest the need for an investigation of the influence of a single treatment class on oxytocin concentrations, to determine whether there is a relationship between oxytocin, the HPA axis (e.g., oxytocin and cortisol) and MDD. Our objective was to measure oxytocin and cortisol in patients with MDD before and following treatment with selective serotonin reuptake inhibitors, SSRI.

METHOD

We sampled blood from arterial plasma. Patients with MDD were studied at the same time twice; pre- and post- 12 weeks treatment, in an unblinded sequential design (clinicaltrials.govNCT00168493).

RESULTS

Results did not reveal differences in oxytocin or cortisol concentrations before relative to following SSRI treatment, and there were no significant relationships between oxytocin and cortisol, or these two physiological variables and psychological symptom scores, before or after treatment.

CONCLUSIONS

These outcomes demonstrate that symptoms of MDD were reduced following effective treatment with an SSRI, and further, stress physiology was unlikely to be a key factor in this outcome. Further research is required to discriminate potential differences in underlying stress physiology for individuals with MDD who respond to antidepressant treatment, relative to those who experience treatment resistance.

Imaging oxytocin × dopamine interactions: an epistasis effect of CD38 and COMT gene variants influences the impact of oxytocin on amygdala activation to social stimuli

Although oxytocin (OT) has become a major target for the investigation of positive social processes, it can be assumed that it exerts its effects in concert with other neurotransmitters. One candidate for such an interaction is dopamine (DA). For both systems, genetic variants have been identified that influence the availability of the particular substance. A variant of the gene coding for the transmembrane protein CD38 (rs3796863), which is engaged in OT secretion, has been associated with OT plasma level. The common catechol-O-methyltransferase (COMT) val158met polymorphism is known to influence COMT activity and therefore the degradation of DA. The present study aimed to investigate OT × DA interactions in the context of an OT challenge study. Hence, we tested the influence of the above mentioned genetic variants and their interaction on the activation of different brain regions (amygdala, VTA, ventral striatum and fusiform gyrus) during the presentation of social stimuli. In a pharmacological cross-over design 55 participants were investigated under OT and placebo (PLA) by means of fMRI. Brain imaging results revealed no significant effects for VTA or ventral striatum. Regarding the fusiform gyrus, we could not find any effects apart from those already described in Sauer et al. (2012). Analyses of amygdala activation resulted in no gene main effect, no gene × substance interaction but a significant gene × gene × substance interaction. While under PLA the effect of CD38 on bilateral amygdala activation to social stimuli was modulated by the COMT genotype, no such epistasis effect was found under OT. Our results provide evidence for an OT × DA interaction during responses to social stimuli. We postulate that the effect of central OT secretion on amygdala response is modulated by the availability of DA. Therefore, for an understanding of the effect of social hormones on social behavior, interactions of OT with other transmitter systems have to be taken into account.

Helping oxytocin deliver: considerations in the development of oxytocin-based therapeutics for brain disorders

Concerns regarding a drought in psychopharmacology have risen from many quarters. From one perspective, the wellspring of bedrock medications for anxiety disorders, depression, and schizophrenia was serendipitously discovered over 30 year ago, the swell of pharmaceutical investment in drug discovery has receded, and the pipeline's flow of medications with unique mechanisms of action (i.e., glutamatergic agents, CRF antagonists) has slowed to a trickle. Might oxytocin (OT)-based therapeutics be an oasis? Though a large basic science literature and a slowly increasing number of studies in human diseases support this hope, the bulk of extant OT studies in humans are single-dose studies on normals, and do not directly relate to improvements in human brain-based diseases. Instead, these studies have left us with a field pregnant with therapeutic possibilities, but barren of definitive treatments. In this clinically oriented review, we discuss the extant OT literature with an eye toward helping OT deliver on its promise as a therapeutic agent. To this end, we identify 10 key questions that we believe future OT research should address. From this overview, several conclusions are clear: (1) the OT system represents an extremely promising target for novel CNS drug development; (2) there is a pressing need for rigorous, randomized controlled clinical trials targeting actual patients; and (3) in order to inform the design and execution of these vital trials, we need further translational studies addressing the questions posed in this review. Looking forward, we extend a cautious hope that the next decade of OT research will birth OT-targeted treatments that can truly deliver on this system's therapeutic potential.

Nocturnal oxytocin secretion is lower in amenorrheic athletes than nonathletes and associated with bone microarchitecture and finite element analysis parameters

OBJECTIVE

Preclinical data indicate that oxytocin, a hormone produced in the hypothalamus and secreted into the peripheral circulation, is anabolic to bone. Oxytocin knockout mice have severe osteoporosis, and administration of oxytocin improves bone microarchitecture in these mice. Data suggest that exercise may modify oxytocin secretion, but this has not been studied in athletes in relation to bone. We therefore investigated oxytocin secretion and its association with bone microarchitecture and strength in young female athletes.

DESIGN

Cross-sectional study of 45 females, 14-21 years (15 amenorrheic athletes (AA), 15 eumenorrheic athletes (EA), and 15 nonathletes (NA)), of comparable bone age and BMI.

METHODS

We used high-resolution peripheral quantitative CT to assess bone microarchitecture and finite element analysis to estimate bone strength at the weight-bearing distal tibia and non-weight-bearing ultradistal radius. Serum samples were obtained every 60  min, 2300-0700  h, and pooled for an integrated measure of nocturnal oxytocin secretion. Midnight and 0700  h samples were used to assess diurnal variation of oxytocin.

RESULTS

Nocturnal oxytocin levels were lower in AA and EA than in NA. After controlling for estradiol, the difference in nocturnal oxytocin between AA and NA remained significant. Midnight and 0700  h oxytocin levels did not differ between groups. At the tibia and radius, AA had impaired microarchitecture compared with NA. In AA, nocturnal oxytocin correlated strongly with trabecular and cortical microarchitecture, particularly at the non-weight-bearing radius. In regression models that include known predictors of microarchitecture in AA, oxytocin accounted for a substantial portion of the variability in microarchitectural and strength parameters.

CONCLUSIONS

Nocturnal oxytocin secretion is low in AA compared with NA and associated with site-dependent microarchitectural parameters. Oxytocin may contribute to hypoestrogenemic bone loss in AA.

Sex, receptors, and attachment: a review of individual factors influencing response to oxytocin

As discussed in the larger review in this special issue (MacDonald and Feifel), intranasal oxytocin (OT) is demonstrating a growing potential as a therapeutic agent in psychiatry. Importantly, research suggests that a variety of individual factors may influence a person's response to OT. In this mini-review, I provide a review of three: (1) sex and hormonal status; (2) genetic variation in aspects of the OT system (i.e., OT receptors); and (3) attachment history. Each of these factors will be important to monitor as we strive to develop a richer understanding of OT's role in human development, brain-based disease, and the potential for individualized, OT-targeted treatments.