Plasma oxytocin and vasopressin do not predict neuropeptide concentrations in human cerebrospinal fluid

Reliability of basal plasma vasopressin concentrations in healthy male adults

OBJECTIVE

The neuropeptides oxytocin (OT) and arginine vasopressin (AVP) play important and interrelated roles in modulating mammalian social behaviour. While the OT system has received considerable research attention for its potential to treat psychiatric symptoms, comparatively little is known about the role of the AVP system in human social behaviour. To better understand the intraindividual stability of basal AVP, the present study assessed the reproducibility of basal plasma AVP concentrations.

METHODS

Basal plasma AVP was assessed at four sampling points separated by 8 days, on average, in 16 healthy adult males.

RESULTS

Only one out of six comparisons revealed strong evidence for reproducibility of basal AVP concentrations (visit 2 vs. visit 4: r=0.8, p0.1). The concordance correlation coefficient [0.15, 95% CI (-0.55, 0.73)] also revealed poor overall reproducibility.

CONCLUSION

Poor reliability of basal AVP concentrations suggests future work covarying AVP with trait markers should proceed with careful consideration of intraindividual fluctuations.

Psychophysiological effects of oxytocin on parent-child interactions: A literature review on oxytocin and parent-child interactions

Oxytocin (OT), often called the 'hormone of love' or 'hormone of attachment,' plays a fundamental role in the establishment and quality of parent-infant bonding. However, emerging evidence indicates that OT can also produce antisocial behavior. To clarify these effects, we review studies examining the role of endogenous and exogenous OT on several determinants of attachment: parental sensitivity, and bonding or synchrony in parent-child dyads. Contextual and individual factors moderating the effect of intranasal OT and its peripheral levels are also reviewed. Finally, potential therapeutic applications for OT and current limitations in human OT research are examined. This systematic literature review was based on the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines, with two electronic databases and other bibliographic sources. We identified a total of 47 relevant studies for inclusion in our review. Most of the findings are in accordance with recent ideas that OT administration may increase parent-child prosocial interaction, showing that OT exerts beneficial effects on processes thought to promote bonding, sensitivity, and synchrony. However, we found that OT can induce antisocial behavior (e.g., anxiety) or adverse effects (modulation of maternal care recollections) that are moderated by different contextual (e.g., maltreatment level, presence of unfamiliar people) and individual (attachment style) factors. This review reinforces the importance of context- and individual-dependent factors, which must be taken into account when analyzing the psychophysiological effects of OT.

Endogenous Oxytocin, Vasopressin, and Aggression in Domestic Dogs

Aggressive behavior in dogs poses public health and animal welfare concerns, however the biological mechanisms regulating dog aggression are not well understood. We investigated the relationships between endogenous plasma oxytocin (OT) and vasopressin (AVP)-neuropeptides that have been linked to affiliative and aggressive behavior in other mammalian species-and aggression in domestic dogs. We first validated enzyme-linked immunosorbent assays (ELISAs) for the measurement of free (unbound) and total (free + bound) OT and AVP in dog plasma. In Experiment 1 we evaluated behavioral and neuroendocrine differences between a population of pet dogs with a history of chronic aggression toward conspecifics and a matched control group. Dogs with a history of aggression exhibited more aggressive behavior during simulated encounters with conspecifics, and had lower free, but higher total plasma AVP than matched controls, but there were no group differences for OT. In Experiment 2 we compared OT and AVP concentrations between pet dogs and a population of assistance dogs that have been bred for affiliative and non-aggressive temperaments, and investigated neuroendocrine predictors of individual differences in social behavior within the assistance dog population. Compared to pet dogs, assistance dogs had higher free and total OT, but there were no differences in either measure for AVP. Within the assistance dog population, dogs who behaved more aggressively toward a threatening stranger had higher total AVP than dogs who did not. Collectively these data suggest that endogenous OT and AVP may play critical roles in shaping dog social behavior, including aspects of both affiliation and aggression.

Choir versus Solo Singing: Effects on Mood, and Salivary Oxytocin and Cortisol Concentrations

The quantification of salivary oxytocin (OXT) concentrations emerges as a helpful tool to assess peripheral OXT secretion at baseline and after various challenges in healthy and clinical populations. Both positive social interactions and stress are known to induce OXT secretion, but the relative influence of either of these triggers is not well delineated. Choir singing is an activity known to improve mood and to induce feelings of social closeness, and may therefore be used to investigate the effects of positive social experiences on OXT system activity. We quantified mood and salivary OXT and cortisol (CORT) concentrations before, during, and after both choir and solo singing performed in a randomized order in the same participants (repeated measures). Happiness was increased, and worry and sadness as well as salivary CORT concentrations were reduced, after both choir and solo singing. Surprisingly, salivary OXT concentrations were significantly reduced after choir singing, but did not change in response to solo singing. Salivary OXT concentrations showed high intra-individual stability, whereas salivary CORT concentrations fluctuated between days within participants. The present data indicate that the social experience of choir singing does not induce peripheral OXT secretion, as indicated by unchanged salivary OXT levels. Rather, the reduction of stress/arousal experienced during choir singing may lead to an inhibition of peripheral OXT secretion. These data are important for the interpretation of future reports on salivary OXT concentrations, and emphasize the need to strictly control for stress/arousal when designing similar experiments.

History of child maltreatment and telomere length in immune cell subsets: Associations with stress- and attachment-related hormones

Experiencing maltreatment during childhood can have long-lasting consequences for both mental and physical health. Immune cell telomere length (TL) shortening might be one link between child maltreatment (CM) experiences and adverse health outcomes later in life. While the stress hormone cortisol has been associated with TL attrition, the attachment-related hormone oxytocin may promote resilience. In 15 mothers with and 15 age- and body mass index-matched mothers without CM, we assessed TL in peripheral blood mononuclear cells and selected immune cell subsets (monocytes, naive, and memory cytotoxic T cells) by quantitative fluorescence in situ hybridization, as well as peripheral cortisol and oxytocin levels. Memory cytotoxic T cells showed significantly shorter TL in association with CM, whereas TL in monocytes and naive cytotoxic T cells did not significantly differ between the two groups. Across both groups, cortisol was negatively associated with TL, while oxytocin was positively associated with TL in memory cytotoxic T cells. These results indicate that long-lived memory cytotoxic T cells are most affected by the increased biological stress state associated with CM. Keeping in mind the correlational and preliminary nature of the results, the data suggest that cortisol may have a damaging and oxytocin a protective function on TL.

Plasma and Urinary Oxytocin Trajectories in Extremely Premature Infants During NICU Hospitalization

Extremely premature infants are at great risk for poor neurodevelopmental outcomes, in part because neurologic structures designed to mature in the womb must now do so in the extrauterine environment. Reliable biomarkers of neurodevelopment are especially critical in this population, as behavioral measures can be unreliable due to immaturity of the premature infant nervous system. Oxytocin (OT) has the potential to be a marker of neurobiological processes that offer infant neuroprotection. However, no studies have measured OT in the plasma and urine of premature infants. The purposes of this study were to describe plasma and urine OT levels of premature infants through 34 weeks corrected gestational age (CGA), determine whether plasma and urine OT are correlated, and explore associations between infant demographics and OT trajectories. Plasma and urine from 37 premature infants, born at gestational ages 25-28 6/7 weeks, were longitudinally collected at 14 days of life, then weekly until 34 weeks CGA. Plasma OT decreased with age, at a rate of 15% per week, and exhibited strong stability within infants. Urine OT was not correlated with plasma OT and did not show a significant trend over time; thus, urine may not be a reliable, noninvasive measurement in this population. Apgar score was the only infant demographic characteristic associated with plasma OT. Given the novelty of this work, replication is needed to confirm these findings, and future research should explore potential mechanisms (e.g., stress, normal maturation, and social experiences) that contribute to declining plasma OT levels in premature infants.

Place preferences associated with pups or cocaine change the expression of D2R, V1aR and OTR in the NAcc and MeA and the levels of plasma AVP, OT, T and E2 in mandarin vole fathers

Drug abuse often has negative impacts on parenting behavior. The dopamine (DA), arginine vasopressin (AVP) and oxytocin (OT) systems are involved in paternal behavior and drug-induced behaviors. Mandarin voles (Microtus mandarinus) are socially monogamous rodents with high levels of paternal behavior. The aims of this study were to examine the protein expression levels of the DA 2-type receptor (D2R), AVP receptor 1A(V1aR) and OT receptor (OTR) in the nucleus accumbens (NAcc) and medial amygdala (MeA) as well as the plasma hormone responses after mandarin vole fathers were conditioned with their pups or cocaine. Our experimental models are based on the conditioned place preference (CPP) paradigm. We observed CPP in response to either pup- or cocaine-associated cues in the mandarin vole fathers. Fathers that were conditioned to either pups or cocaine had a lower expression of D2R and V1aR in the NAcc than did controls. Fathers that were conditioned to pups had higher levels of OTR expression in the MeA and higher plasma levels of AVP, OT, estradiol (E2), and lower plasma levels of testosterone (T) than did controls. Fathers that were conditioned to cocaine exhibited lower levels of plasma AVP and T. These results indicate that the reward effects of pup and cocaine are both mediated by D2R, V1aR and OTR in the NAcc and MeA and that there are subtle differences between the pup and cocaine reward mechanisms that are associated with altered plasma AVP, OT, T and E2.

Oxytocin effects in schizophrenia: Reconciling mixed findings and moving forward

Schizophrenia is a severe mental illness that causes major functional impairment. Current pharmacologic treatments are inadequate, particularly for addressing negative and cognitive symptoms of the disorder. Oxytocin, a neuropeptide known to moderate social behaviors, has been investigated as a potential therapeutic for schizophrenia in recent years. Results have been decidedly mixed, leading to controversy regarding oxytocin's utility. In this review, we outline several considerations for interpreting the extant literature and propose a focused agenda for future work that builds on the most compelling findings regarding oxytocin effects in schizophrenia to date. Specifically, we examine underlying causes of heterogeneity in randomized clinical trials (RCTs) conducted thus far and highlight the complexity of the human oxytocin system. We then review evidence of oxytocin's effects on specific deficits in schizophrenia, arguing for further study using objective, precise outcome measures in order to determine whether oxytocin has the potential to improve functional impairment in schizophrenia.

The neurobiology of social deficits in female patients with borderline personality disorder: The importance of oxytocin

BACKGROUND

Social deficits and emotional dysregulation have been suggested as explanations for the relational difficulties experienced by patients with borderline personality disorder (BPD). The neuropeptide oxytocin (OXT) is a possible neurobiological underpinning of these adversities, and this study examines possible correlations between BPD symptomatology and serum OXT.

METHODS

Thirty-eight female participants (BPD group n = 18, matched control group n = 20) with a mean age of 29.5 years (standard deviation 9.2) were assessed for personality disorders, general psychopathology, childhood trauma and perceived stress. OXT was measured in serum samples.

RESULTS

We found no significant difference between patient and control group in terms of OXT levels. However, post hoc analysis showed a relationship in the patient group between civil status and OXT (p < 0.05), indicating higher levels of OXT for patients in a romantic relationship.

DISCUSSION

The idea of OXT as a pro-social love hormone is perhaps too simplistic, and factors like attachment style, exposure to trauma and psychiatric disorders must be considered in order to understand its diverse functions.

CONCLUSIONS

Contrary to our expectations, we did not find lower serum OXT levels in the BPD group. However, BPD patients in a romantic relationship had higher levels of serum OXT than single BPD patients. Copyright © 2017 John Wiley & Sons, Ltd.

The correlation between central and peripheral oxytocin concentrations: A systematic review and meta-analysis

There is growing interest in the role of the oxytocin system in social cognition and behavior. Peripheral oxytocin concentrations are regularly used to approximate central concentrations in psychiatric research, however, the validity of this approach is unclear. Here we conducted a pre-registered systematic search and meta-analysis of correlations between central and peripheral oxytocin concentrations. A search of databases yielded 17 eligible studies, resulting in a total sample size of 516 participants and subjects. Overall, a positive association between central and peripheral oxytocin concentrations was revealed [r=0.29, 95% CI (0.14, 0.42), p<0.0001]. This association was moderated by experimental context [Q_b(4), p=0.003]. While no association was observed under basal conditions (r=0.08, p=0.31), significant associations were observed after intranasal oxytocin administration (r=0.66, p<0.0001), and after experimentally induced stress (r=0.49, p=0.001). These results indicate a coordination of central and peripheral oxytocin release after stress and after intranasal administration. Although popular, the approach of using peripheral oxytocin levels to approximate central levels under basal conditions is not supported by the present results.

Pilot study demonstrates that salivary oxytocin can be measured unobtrusively in preterm infants

Aim

This study assessed the feasibility and obtrusiveness of measuring salivary oxytocin in preterm infants receiving Kangaroo care, because this is a period of maximal bonding or co‐regulation. We also analysed possible influential determinants, including maternal oxytocin.

Methods

The saliva of preterm infants and their mothers was collected prior to, and during, Kangaroo care using cotton swabs and pooled into vials until sufficient volumes were obtained to measure oxytocin levels using a radioimmunoassay. The obtrusiveness of the infants’ collections was measured with a Likert scale.

Results

Saliva was collected unobtrusively prior to, and during, 30 Kangaroo care sessions in 21 preterm infants. This resulted in three vials with sufficient volumes of before‐Kangaroo care saliva and three with during‐Kangaroo care saliva. Oxytocin was detectable in all six vials. The Kangaroo care duration and the intensity of the mother–infant interaction before and during Kangaroo care seemed to be the most important determinants, and these should preferably be standardised in any future trials.

Conclusion

Oxytocin was measured unobtrusively in the pooled saliva of preterm infants both before and during Kangaroo care and could therefore be investigated as a biomarker in future studies.

Oxytocin and Interpersonal Relationships

The neuropeptide oxytocin (OT) has emerged as a potent modulator of diverse aspects of interpersonal relationships. OT appears to work in close interaction with several other neurotransmitter networks, including the dopaminergic reward circuit, and to be dependent on sex-specific hormonal influences. In this chapter, we focus on four main domains of OT and interpersonal relationships, including (1) the protective effect of OT on an individual's ability to withstand stress (i.e., stress buffering), (2) the effect of OT on emotion recognition and empathy, (3) OT's ability to enhance social synchrony and cooperation among individuals, and (4) the effect of OT on an individual's perception of social touch. We then illustrate the connection between OT and loneliness while grieving the loss of a loved one. We finish by discussing the clinical potential of OT, focusing on its potential role as an adjunct to psychotherapy, its enhancement through sex-specific hormonal influences, and the difficulties that present themselves when considering OT as a therapy. Overall, we argue that OT continues to hold strong therapeutic promise, but that it is strongly dependent on internal and external influences, for instance the patient's personal past experiences and interaction with the therapist, in order to provide the best possible therapy.

Oxytocin pathways in the intergenerational transmission of maternal early life stress

Severe stress in early life, such as childhood abuse and neglect, constitutes a major risk factor in the etiology of psychiatric disorders and somatic diseases. Importantly, these long-term effects may impact the next generation. The intergenerational transmission of maternal early life stress (ELS) may occur via pre-and postnatal pathways, such as alterations in maternal-fetal-placental stress physiology, maternal depression during pregnancy and postpartum, as well as impaired mother-offspring interactions. The neuropeptide oxytocin (OT) has gained considerable attention for its role in modulating all of these assumed transmission pathways. Moreover, central and peripheral OT signaling pathways are highly sensitive to environmental exposures and may be compromised by ELS with implications for these putative transmission mechanisms. Together, these data suggest that OT pathways play an important role in the intergenerational transmission of maternal ELS in humans. By integrating recent studies on gene-environment interactions and epigenetic modifications in OT pathway genes, the present review aims to develop a conceptual framework of intergenerational transmission of maternal ELS that emphasizes the role of OT.

Urinary and plasma oxytocin changes in response to MDMA or intranasal oxytocin administration

BACKGROUND

The neuropeptide oxytocin (OT) has received increased experimental attention for its putative role in both normal social functioning and several psychiatric disorders that are partially characterized by social dysfunction (e.g., autism spectrum disorders: ASD). Many human experimental studies measure circulating plasma levels of OT in order to examine the relationship between the hormone and behavior. Urinary OT (uOT) assays offer a simple, easy, and non-invasive method to measure peripheral hormone levels, but the correspondence between uOT and plasma OT (pOT) levels is unclear. Here, we conducted two within-subjects, double-blind studies exploring changes in uOT and pOT levels following administration of two drugs: MDMA, an oxytocin-releasing drug (Study 1), and intranasal oxytocin (INOT: Study 1 and 2).

METHODS

In Study 1, 14 adult participants (2 females) were each administered either oral 1.5mg/kg MDMA or 40IU INOT across two different study sessions. In Study 2, 10 male participants (adolescents and young adults) diagnosed with ASD received either 40IU INOT or placebo across two different sessions. In both studies, blood and urine samples were collected before and after drug administration at each study session. For Study 1, 10 participants provided valid plasma and urine samples for the MDMA session, and 8 provided valid samples for the INOT session. For Study 2, all 10 participants provided valid samples for both INOT and placebo sessions. Pre- and post-administration levels of pOT and uOT were compared. Additionally, correlations between percent change from baseline uOT and pOT levels were examined.

RESULTS

Study 1: Plasma OT and uOT levels significantly increased after administration of MDMA and INOT. Furthermore, uOT levels were positively correlated with pOT levels following administration of MDMA (r=0.57, p=0.042) but not INOT (r=0.51, p=0.097). Study 2: There was a significant increase in uOT levels after administration of INOT, but not after administration of placebo. Under both conditions, INOT and placebo, significant increases in pOT levels were not observed. Additionally, change from baseline uOT and pOT levels were positively correlated (r=0.57, p=0.021). There was no significant correlation between uOT and pOT levels following placebo administration.

CONCLUSION

Our results show a measurable and significant increase in pOT and uOT levels after the administration of MDMA (Study 1) and INOT (Study 1 and Study 2). Additionally, a positive correlation between uOT and pOT levels was observed in both samples (healthy adults and ASD patients) in at least one condition. However, uOT and pOT levels were not correlated under all conditions, suggesting that uOT levels do not fully correspond to pOT levels in the time windows we measured. Future studies should further examine the relationship between levels of pOT and uOT in healthy and clinical populations on measures of social behavior because uOT may serve as an additional non-invasive method to measure peripheral OT changes.

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

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

Peripheral oxytocin and vasopressin: Biomarkers of psychiatric disorders? A comprehensive systematic review and preliminary meta-analysis

A large array of studies have investigated peripheral oxytocin (OT) and vasopressin (ADH) as potential biomarkers of psychiatric disorders, with highly conflicting and heterogenous findings. We searched Web of KnowledgeSM and Scopus® for English original articles investigating OT and/or ADH levels in different biological fluids (plasma/serum, saliva, urine and cerebrospinal fluid) across several psychiatric disorders. Sixty-four studies were included. We conducted 19 preliminary meta-analyses addressing OT alterations in plasma/serum, saliva, urine and cerebrospinal fluid of 7 psychiatric disorders and ADH alterations in plasma/serum, saliva, urine and cerebrospinal fluid of 6 psychiatric disorders compared to controls. Hedge's g was used as effect size measure, together with heterogeneity analyses, test of publication biases and quality control. None of them (except serum OT in anorexia nervosa) revealed significant differences. There is no convincing evidence that peripheral ADH or OT might be reliable biomarkers in psychiatric disorders. However, the lack of significant results was associated with high methodological heterogeneity, low quality of the studies, small sample size, and scarce reliability of the methods used in previous studies, which need to be validated and standardized.

Genetic Syndromes, Maternal Diseases and Antenatal Factors Associated with Autism Spectrum Disorders (ASD)

Autism spectrum disorder (ASD) affecting about 1% of all children is associated, in addition to complex genetic factors, with a variety of prenatal, perinatal, and postnatal etiologies. In addition, ASD is often an important clinical presentation of some well-known genetic syndromes in human. We discuss these syndromes as well as the role of the more important prenatal factors affecting the fetus throughout pregnancy which may also be associated with ASD. Among the genetic disorders we find Fragile X, Rett syndrome, tuberous sclerosis, Timothy syndrome, Phelan-McDermid syndrome, Hamartoma tumor syndrome, Prader-Willi and Angelman syndromes, and a few others. Among the maternal diseases in pregnancy associated with ASD are diabetes mellitus (PGDM and/or GDM), some maternal autoimmune diseases like antiphospholipid syndrome (APLS) with anti-β2GP1 IgG antibodies and thyroid disease with anti-thyroid peroxidase (TPO) antibodies, preeclampsia and some other autoimmune diseases with IgG antibodies that might affect fetal brain development. Other related factors are maternal infections (rubella and CMV with fetal brain injuries, and possibly Influenza with fever), prolonged fever and maternal inflammation, especially with changes in a variety of inflammatory cytokines and antibodies that cross the placenta and affect the fetal brain. Among the drugs are valproic acid, thalidomide, misoprostol, and possibly SSRIs. β2-adrenergic receptor agonists and paracetamol have also lately been associated with increased rate of ASD but the data is too preliminary and inconclusive. Associations were also described with ethanol, cocaine, and possibly heavy metals, heavy smoking, and folic acid deficiency. Recent studies show that heavy exposure to pesticides and air pollution, especially particulate matter < 2.5 and 10 μm in diameter (PM2.5 and PM10) during pregnancy is also associated with ASD. Finally, we have to remember that many of the associations mentioned in this review are only partially proven, and not all are "clean" of different confounding factors. The associations described in this review emphasize again how little we know about the etiology and pathogenesis of ASD. It is obvious that we need more epidemiologic data to establish many of these associations, but if proven, they might be promising avenues for prevention.

Effects of positive and negative human contacts and intranasal oxytocin on cerebrospinal fluid oxytocin

Despite the popularity of oxytocin (OT) research for its role in social behavior, the relationship between the social environment and endogenous central OT remains poorly understood. This study investigated the effects of positive and negative human contacts and intranasal OT administration on OT concentration in the cerebrospinal fluid (CSF). The pig was used as a model, with repeated CSF sampling through a spinal catheter using a within-subject design. Positive human contact led to sustained CSF OT elevation in pigs over 120min which outlasted the 15min interaction. Furthermore, the frequency of positive interactions was correlated with CSF OT increase. This provides a neurophysiological basis to positive human-animal relationships, with OT preserving bonds within but also between species through interactions. Conversely, CSF OT concentration did not vary during or after negative contact with an unfamiliar person, supporting CSF OT as a biomarker of positive valence in the human-animal relationship context. Intranasal OT administration resulted in peak CSF OT within 10min, with approximately 0.001% of the administered dose reaching the CSF. The sensitivity of the oxytocinergic system to variations in the social environment is a worthy area of investigation for its scientific and clinical implications. In particular, positive interactions result in outlasting central OT release.

Plasma Oxytocin and Arginine-Vasopressin Levels in Children with Autism Spectrum Disorder in China: Associations with Symptoms

Autism spectrum disorder (ASD) is defined by impairments of social interaction and the presence of obsessive behaviors. The "twin" nonapeptides oxytocin (OXT) and arginine-vasopressin (AVP) are known to play regulatory roles in social behaviors. However, the plasma levels and behavioral relevance of OXT and AVP in children with ASD have seldom been investigated. It is also unknown whether their mothers have abnormal plasma peptide levels. Here, using well-established methods of neuropeptide measurement and a relatively large sample size, we determined the plasma levels of the two neuropeptides in 85 normal children, 84 children with ASD, and 31 mothers from each group of children. As expected, children with ASD had lower plasma OXT levels than gender-matched controls (P = 0.028). No such difference was found for plasma AVP concentrations. Correlation analysis showed that ASD children with higher plasma OXT concentrations tended to have less impairment of verbal communication (Rho = -0.22, P = 0.076), while those with higher plasma AVP levels tended to have lower levels of repetitive use of objects (Rho = -0.231, P = 0.079). Unlike the findings in children, maternal plasma OXT levels showed no group difference. However, plasma AVP levels in the mothers of ASD children tended to be lower than in the mothers of normal children (P = 0.072). In conclusion, our results suggest that the OXT system is dysregulated in children with ASD, and that OXT and AVP levels in plasma seem to be associated with specific autistic symptoms. The plasma levels of OXT or AVP in mothers and their ASD children did not seem to change in the same direction.

Effects of oxytocin administration on spirituality and emotional responses to meditation

The oxytocin (OT) system, critically involved in social bonding, may also impinge on spirituality, which is the belief in a meaningful life imbued with a sense of connection to a Higher Power and/or the world. Midlife male participants (N = 83) were randomly assigned to receive intranasal OT or placebo. In exploratory analyses, participants were also genotyped for polymorphisms in two genes critical for OT signaling, the oxytocin receptor gene (OXTR rs53576) and CD38 (rs6449182 and rs3796863). Results showed that intranasal OT increased self-reported spirituality on two separate measures and this effect remained significant a week later. It also boosted participants' experience of specific positive emotions during meditation, at both explicit and implicit levels. Furthermore, the effect of OT on spirituality was moderated by OT-related genotypes. These results provide the first experimental evidence that spirituality, endorsed by millions worldwide, appears to be supported by OT.

A Spatiotemporal Profile of In Vivo Cerebral Blood Flow Changes Following Intranasal Oxytocin in Humans

BACKGROUND

Animal and human studies highlight the role of oxytocin in social cognition and behavior and the potential of intranasal oxytocin (IN-OT) to treat social impairment in individuals with neuropsychiatric disorders such as autism. However, extensive efforts to evaluate the central actions and therapeutic efficacy of IN-OT may be marred by the absence of data regarding its temporal dynamics and sites of action in the living human brain.

METHODS

In a placebo-controlled study, we used arterial spin labeling to measure IN-OT-induced changes in resting regional cerebral blood flow (rCBF) in 32 healthy men. Volunteers were blinded regarding the nature of the compound they received. The rCBF data were acquired 15 min before and up to 78 min after onset of treatment onset (40 IU of IN-OT or placebo). The data were analyzed using mass univariate and multivariate pattern recognition techniques.

RESULTS

We obtained robust evidence delineating an oxytocinergic network comprising regions expected to express oxytocin receptors, based on histologic evidence, and including core regions of the brain circuitry underpinning social cognition and emotion processing. Pattern recognition on rCBF maps indicated that IN-OT-induced changes were sustained over the entire posttreatment observation interval (25-78 min) and consistent with a pharmacodynamic profile showing a peak response at 39-51 min.

CONCLUSIONS

Our study provides the first visualization and quantification of IN-OT-induced changes in rCBF in the living human brain unaffected by cognitive, affective, or social manipulations. Our findings can inform theoretical and mechanistic models regarding IN-OT effects on typical and atypical social behavior and guide future experiments (e.g., regarding the timing of experimental manipulations).

Effect of breastfeeding on haemodynamics and consumption of propofol and sevoflurane: A state entropy guided comparative study

Background and Aims:

Unique post-partum endocrine hormone oxytocin secreted during breastfeeding (BF) has amnestic, sedative properties and down-regulates stress responses. This study was done to assess the effect of BF on consumption of propofol, sevoflurane and haemodynamic stability in women.

Methods:

Study was conducted on 120 women aged 20–30 years of American Society of Anesthesiologists I and II physical status scheduled for tubectomy under general anaesthesia who were randomly allocated to three groups 40 of each; BF, withhold feeding (WF), and non-feeding (NF) groups. All received standard premedication. Heart rate (HR), mean arterial pressure (MAP) and state entropy (SE) values were recorded at regular intervals. All patients were induced with intravenous propofol until the SE levels dropped to 45, and dose of propofol recorded. Airway was secured with laryngeal mask airway and anaesthesia was maintained with sevoflurane in 60% N₂O and O₂. Sevoflurane concentration was adjusted to maintain SE between 40 and 60. End tidal concentration of sevoflurane and consumption of sevoflurane (ml) was recorded by GE Datex-Ohmeda S/5™ System. Results were analysed by analysis of variance and Chi-square test.

Results:

Demographic parameters were comparable. Dose of propofol and sevoflurane consumption in group BF was significantly reduced by 20% and 35%, respectively (P < 0.05) compared to group NF. Intra-operative HR and MAP were persistently low in group BF and elevated in group WF (P < 0.05).

Conclusion:

BF before induction of anaesthesia decreases the consumption of propofol, sevoflurane and maintains the intra-operative haemodynamic stability, whereas withholding BF increases propofol and sevoflurane consumption with intra-operative higher HR and MAP, compared to control group.

Plasma and CSF oxytocin levels after intranasal and intravenous oxytocin in awake macaques

Oxytocin (OT) is a neuropeptide that mediates a variety of complex social behaviors in animals and humans. Intranasal OT has been used as an experimental therapeutic for human conditions characterized by deficits in social functioning, especially autism spectrum disorder and schizophrenia. However, it is currently under intense debate whether intranasal delivery of OT reaches the central nervous system. In this study, four female rhesus macaques were implanted with chronic intrathecal catheters and used to investigate the pharmacokinetic profile of OT in the central nervous system and the peripheral vasculature following intravenous (IV) and intranasal (IN) administration of OT. In a randomized, crossover design, OT was given to four awake monkeys at three different doses based on body weight (0.1 IU/kg; 1 IU/kg; 5 IU/kg). A time course of concurrent cerebrospinal fluid (CSF) and plasma samples were taken following administration. We found a dose-dependent effect of IV OT treatment on plasma OT levels, which peaked at 5 min post-dose and gradually returned to baseline by 120 min. In contrast, a change in CSF OT was only observed at the highest IV dose (5 IU/kg) at 15 min post-dose and gradually returned to baseline by 120 min. After IN administration, there was no significant change in plasma OT at any of the three doses. However, at the highest dose level, we found a significant increase in CSF OT at 15-30 min post- dose. The results of this study in light of recent, similar publications highlight the importance of methodological consistency across studies. This study also establishes a non-human primate model that can provide a stable platform for carrying out serial sampling from the central nervous system and peripheral vasculature concurrently.

Chronic Methamphetamine Self-Administration Dysregulates Oxytocin Plasma Levels and Oxytocin Receptor Fibre Density in the Nucleus Accumbens Core and Subthalamic Nucleus of the Rat

The neuropeptide oxytocin attenuates reward and abuse for the psychostimulant methamphetamine (METH). Recent findings have implicated the nucleus accumbens (NAc) core and subthalamic nucleus (STh) in oxytocin modulation of acute METH reward and relapse to METH-seeking behaviour. Surprisingly, the oxytocin receptor (OTR) is only modestly involved in both regions in oxytocin attenuation of METH-primed reinstatement. Coupled with the limited investigation of the role of the OTR in psychostimulant-induced behaviours, we primarily investigated whether there are cellular changes to the OTR in the NAc core and STh, as well as changes to oxytocin plasma levels, after chronic METH i.v. self-administration (IVSA) and after extinction of drug-taking. An additional aim was to examine whether changes to central corticotrophin-releasing factor (CRF) and plasma corticosterone levels were also apparent because of the interaction of oxytocin with stress-regulatory mechanisms. Male Sprague-Dawley rats were trained to lever press for i.v. METH (0.1 mg/kg/infusion) under a fixed-ratio 1 schedule or received yoked saline infusions during 2-h sessions for 20 days. An additional cohort of rats underwent behavioural extinction for 15 days after METH IVSA. Subsequent to the last day of IVSA or extinction, blood plasma was collected for enzyme immunoassay, and immunofluorescence was conducted on NAc core and STh coronal sections. Rats that self-administered METH had higher oxytocin plasma levels, and decreased OTR-immunoreactive (-IR) fibres in the NAc core than yoked controls. In animals that self-administered METH and underwent extinction, oxytocin plasma levels remained elevated, OTR-IR fibre density increased in the STh, and a trend towards normalisation of OTR-IR fibre density was evident in the NAc core. CRF-IR fibre density in both brain regions and corticosterone plasma levels did not change across treatment groups. These findings demonstrate that oxytocin systems, both centrally within the NAc core and STh, as well as peripherally through plasma measures, are dysregulated after METH abuse.

The relationship between central and peripheral oxytocin concentrations: a systematic review and meta-analysis protocol

BACKGROUND

Research examining the effects of oxytocin (OT) interventions on psychiatric, social-behavioral, and social-cognitive outcomes regularly collect peripheral levels of OT as markers of central bioavailability. Such inferences rest on the assumption that central and peripheral levels of OT are directly associated. However, conflicting evidence from coordinated sampling of central and peripheral OT question the validity of this assumption. The purpose of this meta-analysis is to evaluate the correlation between central and peripheral OT, as well as to account for potential heterogeneity in the literature.

METHODS/DESIGN

Studies that report coordinated sampling of central and peripheral OT in humans and animals will be identified. Research investigating concentrations in both basal states and after exogenous administration will be considered. PubMed and Embase databases will be searched, along with citation lists of retrieved articles. Peer-reviewed studies written in English published from 1971 onwards will be included in the meta-analysis. Data will be extracted from eligible studies for a random-effects meta-analysis. For each study, a summary effect size, heterogeneity, risk of bias, publication bias, and the effect of categorical and continuous moderator variables will be determined.

DISCUSSION

This systematic review and meta-analysis will identify and synthesize evidence to determine if there is an association between central and peripheral OT concentrations. If significant associations are observed, evidence would provide a rationale for future research to use peripheral measures as a proxy for central OT concentrations.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42015027864.

Potential of Oxytocin in the Treatment of Schizophrenia

Schizophrenia is a heterogeneous, debilitating disorder characterized by three distinct sets of clinical features: positive symptoms, negative symptoms, and cognitive deficits. Extant antipsychotic drugs have been most successful at treating the positive symptoms of patients with schizophrenia but have minimal therapeutic effects on negative symptoms and cognitive deficits, which are the symptoms that best predict the poor prognosis of these patients. Therefore, there has been a major effort towards identifying compounds that alleviate these symptoms. Oxytocin (OT) is a nonapeptide that regulates peripheral reproductive-relevant functions, and also acts as a neurotransmitter in the brain. Converging evidence from both preclinical and clinical research suggests that OT may have therapeutic efficacy for the positive symptoms, negative symptoms, and cognitive deficits of schizophrenia. In the majority of the small, randomized, placebo-controlled clinical trials conducted to date, OT has shown particular promise in its potential to treat the intractable negative symptoms and social cognitive deficits exhibited by most of the patients with this debilitating disorder. In this leading article, we summarize the clinical evidence relevant to (1) endogenous OT and schizophrenia, and (2) the putative therapeutic effects of OT on each of the three clinical domains.

Intranasal Oxytocin: Myths and Delusions

Despite widespread reports that intranasal application of oxytocin has a variety of behavioral effects, very little of the huge amounts applied intranasally appears to reach the cerebrospinal fluid. However, peripheral concentrations are increased to supraphysiologic levels, with likely effects on diverse targets including the gastrointestinal tract, heart, and reproductive tract. The wish to believe in the effectiveness of intranasal oxytocin appears to be widespread and needs to be guarded against with scepticism and rigor. Preregistering trials, declaring primary and secondary outcomes in advance, specifying the statistical methods to be applied, and making all data openly available should minimize problems of publication bias and questionable post hoc analyses. Effects of intranasal oxytocin also need proper dose-response studies, and such studies need to include control subjects for peripheral effects, by administering oxytocin peripherally and by blocking peripheral actions with antagonists. Reports in the literature of oxytocin measurements include many that have been made with discredited methodology. Claims that peripheral measurements of oxytocin reflect central release are questionable at best.

Dissecting the Role of Oxytocin in the Formation and Loss of Social Relationships

Current concepts of human sociality highlight a fundamental role of the hypothalamic peptide oxytocin (OXT) in the formation and maintenance of social relationships. However, emerging evidence indicates that OXT does not invariably facilitate social bonding but also produces nonprosocial effects that may have evolved to promote offspring survival. From a mechanistic perspective, we hypothesize that OXT modulates interoceptive signals and self-referential processing, which may result in various social outcomes depending on context- and person-dependent variables such as early-life adversity. Based on this theoretical framework, we discuss translational implications for clinical trials and identify open questions for future research. Specifically, we propose that disrupted OXT signaling due to the loss of affectionate bonds may contribute to emotional disequilibrium and confer elevated risk for the onset of stress-related disorders.

The Neurobiology Shaping Affective Touch: Expectation, Motivation, and Meaning in the Multisensory Context

Inter-individual touch can be a desirable reward that can both relieve negative affect and evoke strong feelings of pleasure. However, if other sensory cues indicate it is undesirable to interact with the toucher, the affective experience of the same touch may be flipped to disgust. While a broad literature has addressed, on one hand the neurophysiological basis of ascending touch pathways, and on the other hand the central neurochemistry involved in touch behaviors, investigations of how external context and internal state shapes the hedonic value of touch have only recently emerged. Here, we review the psychological and neurobiological mechanisms responsible for the integration of tactile “bottom–up” stimuli and “top–down” information into affective touch experiences. We highlight the reciprocal influences between gentle touch and contextual information, and consider how, and at which levels of neural processing, top-down influences may modulate ascending touch signals. Finally, we discuss the central neurochemistry, specifically the μ-opioids and oxytocin systems, involved in affective touch processing, and how the functions of these neurotransmitters largely depend on the context and motivational state of the individual.

Do blood plasma levels of oxytocin moderate the effect of nasally administered oxytocin on social orienting in high-functioning male adults with autism spectrum disorder?

OBJECTIVE

The study investigated whether baseline plasma oxytocin (OXT) concentrations might moderate the effects of nasally administered OXT on social orienting.

METHODS

Thirty-one males with Autism spectrum disorder (ASD) and thirty healthy males participated in a double-blind placebo-controlled crossover trial. After administration of the compound, participants were viewing pictures from the International Affective Picture System that represented a systematic variation of pleasant, unpleasant and neutral scenes with and without humans. The outcome measures were a cardiac evoked response (ECR) and a cortical evoked long latency parietal positivity (LPP).

RESULTS

Males with ASD had significantly higher plasma baseline levels than the controls. In the absence of general treatment effects, higher baseline concentrations were found to be associated with larger treatment effects, particularly in the group of males with ASD. Higher post-treatment plasma OXT concentrations were found to be associated with smaller treatment effects and larger orienting responses in the placebo situation in the group of controls.

CONCLUSIONS

We interpret our findings as suggesting that it is the central availability of OXT determining how much of the nasally administered OXT will become centrally absorbed and how much of it will become released into the bloodstream.

Salivary oxytocin concentrations in response to running, sexual self-stimulation, breastfeeding and the TSST: The Regensburg Oxytocin Challenge (ROC) study

Intranasal oxytocin (OXT) application is emerging as a potential treatment for socio-emotional disorders associated with abnormalities in OXT system (re-) activity. The crucial identification of patients with such abnormalities could be streamlined by the assessment of basal and stimulus-induced OXT concentrations in saliva, using a simple, stress-free sampling procedure (i.e. an OXT challenge test). We therefore established the Regensburg Oxytocin Challenge (ROC) test to further validate salivary OXT concentrations as a practical, reliable and sensitive biomarker. OXT concentrations were quantified by radioimmunoassay in samples collected at home by healthy adult male and female volunteers before and after running ("Run") or sexual self-stimulation ("Sex"). In lactating women, salivary OXT concentrations were quantified before, during and after breastfeeding. Salivary OXT along with salivary cortisol and heart rate were monitored in healthy adult participants undergoing the Trier Social Stress Test (TSST). The home-based "Run" and "Sex" challenges as well as the laboratory-based TSST caused quantifiable, rapid, and consistent increases in salivary OXT (approximately 2.5-fold after 10-15min), which were similar for men and women. Breastfeeding did not result in measurably increased salivary OXT levels, probably because the short pulses of OXT release characteristic for lactation were missed. Taken together, ROC tests reliably assess the responsiveness of the OXT system (i.e., the increase in salivary OXT concentrations as compared to basal levels) to challenges such as "Run" and "Sex" at home or psychosocial stress (TSST) in the laboratory. Further studies with larger sample numbers are essentially needed in order to reveal individual differences in ROC test outcomes depending on, for example, genetic or environmental factors.

Does Oxytocin Increase Trust in Humans? A Critical Review of Research

Behavioral neuroscientists have shown that the neuropeptide oxytocin (OT) plays a key role in social attachment and affiliation in nonhuman mammals. Inspired by this initial research, many social scientists proceeded to examine the associations of OT with trust in humans over the past decade. To conduct this work, they have (a) examined the effects of exogenous OT increase caused by intranasal administration on trusting behavior, (b) correlated individual difference measures of OT plasma levels with measures of trust, and (c) searched for genetic polymorphisms of the OT receptor gene that might be associated with trust. We discuss the different methods used by OT behavioral researchers and review evidence that links OT to trust in humans. Unfortunately, the simplest promising finding associating intranasal OT with higher trust has not replicated well. Moreover, the plasma OT evidence is flawed by how OT is measured in peripheral bodily fluids. Finally, in recent large-sample studies, researchers failed to find consistent associations of specific OT-related genetic polymorphisms and trust. We conclude that the cumulative evidence does not provide robust convergent evidence that human trust is reliably associated with OT (or caused by it). We end with constructive ideas for improving the robustness and rigor of OT research.

Salivary oxytocin increases concurrently with testosterone and time away from home among returning Tsimane' hunters

Oxytocin, testosterone and cortisol can have opposing effects on social behaviour, yet few studies have examined their interactions. We measured changes in salivary oxytocin, testosterone and cortisol among Tsimane' men returning home after hunting, an ancient context of male status competition, parental investment and cooperation. Contra normal diurnal rhythm, oxytocin increased relative to baseline and this increase was positively associated with duration of the hunt and change in testosterone, but not cortisol, social context, hunting outcome or physical activity. The concurrent increase in endogenous peripheral oxytocin and testosterone is unexpected given their opposing independent effects on social cognition and behaviour, and has not been observed before. We discuss the potential significance of these effects for the biology of pair-bonding, parenting and social foraging in humans and other species.

The neuropeptide oxytocin modulates consumer brand relationships

Each year, companies invest billions of dollars into marketing activities to embellish brands as valuable relationship partners assuming that consumer brand relationships (CBRs) and interpersonal relationships rest upon the same neurobiological underpinnings. Given the crucial role of the neuropeptide oxytocin (OXT) in social bonding, this study tests whether OXT-based mechanisms also determine the bond between consumers and brands. We conducted a randomized, placebo-controlled study involving 101 subjects and analyzed the effect of intranasal OXT on consumers’ attribution of relationship qualities to brands, brands paired with human celebrity endorsers, and familiar persons. OXT indeed promoted the attribution of relationship qualities not only in the case of social and semi-social stimuli, but also brands. Intriguingly, for subjects scoring high on autistic-like traits, the effect of OXT was completely reversed, evident in even lower relationship qualities across all stimulus categories. The importance of OXT in a CBR context is further corroborated by a three-fold increase in endogenous release of OXT following exposure to one’s favorite brand and positive associations between baseline peripheral OXT concentrations and brand relationship qualities. Collectively, our findings indicate that OXT not only plays a fundamental role in developing interpersonal relationships, but also enables relationship formation with objects such as brands.

Salivary Oxytocin and Vasopressin Levels in Police Officers With and Without Post-Traumatic Stress Disorder

Post-traumatic stress disorder (PTSD) is characterised by symptoms associated with maladaptive fear and stress responses, as well as with social detachment. The neuropeptides oxytocin (OT) and arginine vasopressin (AVP) have been associated with both regulating fear and neuroendocrine stress responsiveness and social behaviour. However, there is only limited evidence for dysregulated peripheral OT and AVP levels in PTSD patients. The present study aimed to investigate basal salivary OT and AVP levels in trauma-exposed male and female police officers with and without PTSD. Saliva samples were collected during rest and OT and AVP levels were determined using a radioimmunoassay. Men and women were analysed separately, having adjusted for differences in trauma history, and for hormonal contraception use in women. The results showed that male PTSD patients had lower basal salivary OT levels, and did not differ in AVP levels compared to male trauma-exposed healthy controls after adjusting for childhood emotional abuse. There were no significant differences in basal salivary OT and AVP levels in women. Our findings indicate potential dysfunctioning of the OT system in male PTSD patients. Future studies are needed to replicate these findings and to further unravel the relationship between the OT and AVP systems, sex, trauma history and PTSD.

A human tendency to anthropomorphize is enhanced by oxytocin

In the course of human evolution, the brain has evolved into a highly sensitive detector of social signals. As a consequence of this socially driven adaptation, humans display a tendency to anthropomorphize, that is they attribute social meaning to non-social agents. The evolutionarily highly conserved hypothalamic peptide oxytocin (OXT) has been identified as a key factor attaching salience to socially relevant cues, but whether it contributes to spontaneous anthropomorphism is still elusive. In the present study involving 60 healthy female participants, we measured salivary OXT concentrations and explored the effect of a single intranasal dose of synthetic OXT (24 IU) or placebo (PLC) on anthropomorphic tendencies during participants׳ verbal descriptions of short video clips depicting socially and non-socially moving geometric shapes. Our results show that endogenous OXT concentrations at baseline positively correlated with the attribution of animacy to social stimuli. While intranasal OXT had no modulatory effect on arousal ratings and did not make the participants more talkative, the treatment boosted anthropomorphic descriptions specifically for social stimuli. In conclusion, we here provide first evidence indicating that spontaneous anthropomorphism in women is facilitated by oxytocin, thereby enabling a context-specific upregulation of the propensity to anthropomorphize environmental cues.

Cerebrospinal fluid and plasma oxytocin concentrations are positively correlated and negatively predict anxiety in children

The neuropeptide oxytocin (OXT) exerts anxiolytic and prosocial effects in the central nervous system of rodents. A number of recent studies have attempted to translate these findings by investigating the relationships between peripheral (e.g., blood, urinary and salivary) OXT concentrations and behavioral functioning in humans. Although peripheral samples are easy to obtain in humans, whether peripheral OXT measures are functionally related to central OXT activity remains unclear. To investigate a possible relationship, we quantified OXT concentrations in concomitantly collected cerebrospinal fluid (CSF) and blood samples from child and adult patients undergoing clinically indicated lumbar punctures or other CSF-related procedures. Anxiety scores were obtained in a subset of child participants whose parents completed psychometric assessments. Findings from this study indicate that plasma OXT concentrations significantly and positively predict CSF OXT concentrations (r=0.56, P=0.0064, N=27). Moreover, both plasma (r=-0.92, P=0.0262, N=10) and CSF (r=-0.91, P=0.0335, N=10) OXT concentrations significantly and negatively predicted trait anxiety scores, consistent with the preclinical literature. Importantly, plasma OXT concentrations significantly and positively (r=0.96, P=0.0115, N=10) predicted CSF OXT concentrations in the subset of child participants who provided behavioral data. This study provides the first empirical support for the use of blood measures of OXT as a surrogate for central OXT activity, validated in the context of behavioral functioning. These preliminary findings also suggest that impaired OXT signaling may be a biomarker of anxiety in humans, and a potential target for therapeutic development in individuals with anxiety disorders.

Does salt have a permissive role in the induction of puberty?

Puberty is starting earlier than ever before and there are serious physiological and sociological implications as a result of this development. Current research has focused on the potential role of high caloric, and commensurate high adiposity, contributions to early puberty. However, girls with normal BMI also appear to be initiating puberty earlier. Westernized diets, in addition to being high in fat and sugar, are also high in salt. To date, no research has investigated a link between elevated salt and the reproductive axis. We hypothesize that a high salt diet can result in an earlier onset of puberty through three mechanisms that are not mutually exclusive. (1) High salt activates neurokinin B, a hormone that is involved in both the reproductive axis and salt regulation, and this induces kisspeptin release and ultimate activation of the reproductive axis. (2) Vasopressin released in response to high salt acts on vasopressin receptors expressed on kisspeptin neurons in the anteroventral periventricular nucleus, thereby stimulating gonadotropin releasing hormone and subsequently luteinizing hormone secretion. (3) Salt induces metabolic changes that affect the reproductive axis. Specifically, salt acts indirectly to modulate adiposity, ties in with the obesity epidemic, and further compounds the pathologic effects of obesity. Our overall hypothesis offers an additional cause behind the induction of puberty and provides testable postulates to determine the mechanism of potential salt-mediated affects on puberty.

Plasma oxytocin and personality traits in psychiatric outpatients

The oxytocin system is regarded as being of relevance for social interaction. In spite of this, very few studies have investigated the relationship between oxytocin and personality traits in clinical psychiatric populations. We assessed the relationship between personality traits and plasma oxytocin levels in a population of 101 medication-free psychiatric outpatients (men = 37, women = 64). We used the Karolinska Scale of Personality (KSP) and diagnostic and symptomatic testing. Plasma oxytocin levels were analysed with a specific radioimmunoassay at inclusion and after one month for testing of stability. Plasma oxytocin levels were stable over time and did not differ between patients with or without personality disorders, nor were they related to severity of depressive or anxiety symptoms. The KSP factors Impulsiveness and Negative Emotionality were significant independent predictors of plasma oxytocin. A subscale analysis of these personality factors showed significant positive correlations between baseline plasma oxytocin and the KSP subscales monotony avoidance and psychic anxiety. The significant association between the KSP factor Impulsiveness and oxytocin levels observed at baseline was observed also one month later in men. These findings suggest that personality traits such as Impulsiveness and Negative emotionality which are linked to social functioning in several psychiatric disorders seem to be associated with endogenous plasma oxytocin levels. These variations in oxytocin levels might have an impact on social sensitivity or social motivation with possible gender differences.

Peripheral oxytocin activates vagal afferent neurons to suppress feeding in normal and leptin-resistant mice: a route for ameliorating hyperphagia and obesity

Oxytocin (Oxt), a neuropeptide produced in the hypothalamus, is implicated in regulation of feeding. Recent studies have shown that peripheral administration of Oxt suppresses feeding and, when infused subchronically, ameliorates hyperphagic obesity. However, the route through which peripheral Oxt informs the brain is obscure. This study aimed to explore whether vagal afferents mediate the sensing and anorexigenic effect of peripherally injected Oxt in mice. Intraperitoneal Oxt injection suppressed food intake and increased c-Fos expression in nucleus tractus solitarius to which vagal afferents project. The Oxt-induced feeding suppression and c-Fos expression in nucleus tractus solitarius were blunted in mice whose vagal afferent nerves were blocked by subdiaphragmatic vagotomy or capsaicin treatment. Oxt induced membrane depolarization and increases in cytosolic Ca2+ concentration ([Ca2+]i) in single vagal afferent neurons. The Oxt-induced [Ca2+]i increases were markedly suppressed by Oxt receptor antagonist. These Oxt-responsive neurons also responded to cholecystokinin-8 and contained cocaine- and amphetamine-regulated transcript. In obese diabetic db/db mice, leptin failed to increase, but Oxt increased [Ca2+]i in vagal afferent neurons, and single or subchronic infusion of Oxt decreased food intake and body weight gain. These results demonstrate that peripheral Oxt injection suppresses food intake by activating vagal afferent neurons and thereby ameliorates obesity in leptin-resistant db/db mice. The peripheral Oxt-regulated vagal afferent neuron provides a novel target for treating hyperphagia and obesity.

The neural mediators of kindness-based meditation: a theoretical model

Although kindness-based contemplative practices are increasingly employed by clinicians and cognitive researchers to enhance prosocial emotions, social cognitive skills, and well-being, and as a tool to understand the basic workings of the social mind, we lack a coherent theoretical model with which to test the mechanisms by which kindness-based meditation may alter the brain and body. Here, we link contemplative accounts of compassion and loving-kindness practices with research from social cognitive neuroscience and social psychology to generate predictions about how diverse practices may alter brain structure and function and related aspects of social cognition. Contingent on the nuances of the practice, kindness-based meditation may enhance the neural systems related to faster and more basic perceptual or motor simulation processes, simulation of another's affective body state, slower and higher-level perspective-taking, modulatory processes such as emotion regulation and self/other discrimination, and combinations thereof. This theoretical model will be discussed alongside best practices for testing such a model and potential implications and applications of future work.

Hormones as "difference makers" in cognitive and socioemotional aging processes

Aging is associated with well-recognized alterations in brain function, some of which are reflected in cognitive decline. While less appreciated, there is also considerable evidence of socioemotional changes later in life, some of which are beneficial. In this review, we examine age-related changes and individual differences in four neuroendocrine systems-cortisol, estrogen, testosterone, and oxytocin-as "difference makers" in these processes. This suite of interrelated hormonal systems actively coordinates regulatory processes in brain and behavior throughout development, and their level and function fluctuate during the aging process. Despite these facts, their specific impact in cognitive and socioemotional aging has received relatively limited study. It is known that chronically elevated levels of the stress hormone cortisol exert neurotoxic effects on the aging brain with negative impacts on cognition and socioemotional functioning. In contrast, the sex hormones estrogen and testosterone appear to have neuroprotective effects in cognitive aging, but may decrease prosociality. Higher levels of the neuropeptide oxytocin benefit socioemotional functioning, but little is known about the effects of oxytocin on cognition or about age-related changes in the oxytocin system. In this paper, we will review the role of these hormones in the context of cognitive and socioemotional aging. In particular, we address the aforementioned gap in the literature by: (1) examining both singular actions and interrelations of these four hormonal systems; (2) exploring their correlations and causal relationships with aspects of cognitive and socioemotional aging; and (3) considering multilevel internal and external influences on these hormone systems within the framework of explanatory pluralism. We conclude with a discussion of promising future research directions.

Social cognition

Social cognition is a major problem underlying deficiencies in interpersonal relationships in several psychiatric populations. And yet there is currently no gold standard for pharmacological treatment of psychiatric illness that directly targets these social cognitive areas. This chapter serves to illustrate some of the most innovative attempts at pharmacological modulation of social cognition in psychiatric illnesses including schizophrenia, borderline personality disorder, autism spectrum disorders, antisocial personality disorder and psychopathy, social anxiety disorder, and posttraumatic stress disorder. Pharmacological modulation includes studies administering oxytocin, ecstasy (MDMA), modafinil, methylphenidate, and D-cycloserine. Furthermore, some background on social cognition research in healthy individuals, which could be helpful in developing future treatments, is provided as well as the potential for each drug as a long-term treatment option.

Lithium carbonate in the management of cannabis withdrawal: a randomized placebo-controlled trial in an inpatient setting

RATIONALE

Preclinical studies suggest that lithium carbonate (lithium) can reduce precipitated cannabinoid withdrawal in rats by stimulating release of the neuropeptide oxytocin, while two open-label studies indicate lithium may ameliorate cannabis withdrawal symptoms in humans.

OBJECTIVES

This study was conducted to examine the efficacy and safety of lithium in the inpatient management of cannabis withdrawal and to determine whether lithium affects plasma oxytocin and the rate of elimination of plasma cannabinoids during abstinence.

METHODS

Treatment-seeking cannabis-dependent adults (n = 38) were admitted for 8 days to an inpatient withdrawal unit and randomized to either oral lithium (500 mg) or placebo given twice a day under double-blind randomized controlled trial (RCT) conditions. Primary outcomes included withdrawal severity [cannabis withdrawal scale (CWS)], rates of detoxification completion, and adverse events. Plasma cannabinoids, plasma oxytocin and serum lithium levels were measured repeatedly over admission. Follow-up research interviews were conducted at 14, 30, and 90 days postdischarge.

RESULTS

Lithium did not significantly affect total CWS scores relative to placebo, although it significantly reduced individual symptoms of "loss of appetite," "stomach aches," and "nightmares/strange dreams." No significant group differences were found in treatment retention or adverse events. Lithium did not increase plasma oxytocin levels nor influence the rate of elimination of cannabinoids. Both placebo- and lithium-treated participants showed reduced levels of cannabis use (verified by urinalysis) and improved health and psychosocial outcomes at 30- and 90-day follow-up relative to pretreatment baselines.

CONCLUSIONS

Despite the strong rationale for the present study, the efficacy of lithium over placebo in the management of cannabis withdrawal was not demonstrated.

Autism, oxytocin and interoception

Autism is a pervasive developmental disorder characterized by profound social and verbal communication deficits, stereotypical motor behaviors, restricted interests, and cognitive abnormalities. Autism affects approximately 1% of children in developing countries. Given this prevalence, identifying risk factors and therapeutic interventions are pressing objectives—objectives that rest on neurobiologically grounded and psychologically informed theories about the underlying pathophysiology. In this article, we review the evidence that autism could result from a dysfunctional oxytocin system early in life. As a mediator of successful procreation, not only in the reproductive system, but also in the brain, oxytocin plays a crucial role in sculpting socio-sexual behavior. Formulated within a (Bayesian) predictive coding framework, we propose that oxytocin encodes the saliency or precision of interoceptive signals and enables the neuronal plasticity necessary for acquiring a generative model of the emotional and social 'self.' An aberrant oxytocin system in infancy could therefore help explain the marked deficits in language and social communication—as well as the sensory, autonomic, motor, behavioral, and cognitive abnormalities—seen in autism.

Plasma vasopressin concentrations positively predict cerebrospinal fluid vasopressin concentrations in human neonates

Central arginine vasopressin (AVP) plays a critical role in mammalian social behavior and has been hypothesized to be a biomarker of certain human neurodevelopmental disorders, including autism. However, opportunities to collect post-mortem brain tissue or cerebrospinal fluid (CSF) from children are extremely limited, and the use of less invasive peripheral assessments (e.g., blood, urine, or saliva) of AVP as a proxy for more invasive central measures has not been well validated. Further, almost nothing is known about AVP biology in very young infants. Therefore in the present study we concomitantly collected basal CSF and plasma samples from N = 20 neonates undergoing clinical sepsis evaluation (all were sepsis negative) and quantified AVP concentrations via well-validated enzyme-immunoassay methodology. Plasma AVP concentrations significantly and positively predicted CSF AVP concentrations (r = 0.73, p = 0.0021), and this relationship persisted when variance attributed to sex, gestational age, and sample collection time was controlled for in the statistical model (r = 0.75, p = 0.0047). These findings provide preliminary support for the use of basal plasma AVP measurement as a proxy for basal brain AVP activity in pediatric populations. Future studies are now required to determine the relationship between behavioral measures and AVP concentrations in both central and peripheral compartments in young infants and older children.