Oxytocin strengthens the link between provocation and aggression among low anxiety people

Social isolation induces sexually aggressive behaviour in male Wistar rats

BACKGROUND

Sexual violence, a pervasive global issue, significantly impacts individuals and societies, necessitating a deeper understanding of its underlying biological mechanisms. This study aimed to elucidate the role of stress-induced dysregulation of the hypothalamus-pituitary-adrenocortical axis in sexual aggression in male Wistar rats. Employing a sexual aggression paradigm, we investigated the effects of social isolation on aggression, anxiety-like behaviour, and neurochemistry in virgin adult male Wistar rats.

RESULTS

The results showed that social isolation significantly escalated aggressive behaviours and induced anxiety-like responses in male rats. The sexual aggression test revealed that socially isolated males exhibited heightened aggression towards non-receptive females. Neurochemical analyses indicated significant alterations in key markers, such as corticotrophin-releasing hormone, oxytocin, and arginine vasopressin, correlating with the observed behavioural changes. Gene expression analyses revealed significant findings, particularly in the expression of the oxytocin receptor (OXTR) and vasopressin receptor 1 A (AVPR1A) genes. Social isolation and the duration of aggressive behaviour prior to the sexual aggression test significantly influenced OXTR expression in the hippocampus and AVPR1A expression in both the prefrontal cortex and hippocampus, highlighting the complex interplay between environmental stressors, neurochemical responses, and gene expression in the manifestation of sexual aggression behaviour.

CONCLUSIONS

This study underscores the critical impact of stress and social isolation on sexual aggression, providing valuable insights into possible neurobiological underpinnings of sexual violence. Understanding these mechanisms is crucial for developing effective interventions to mitigate the consequences of sexual aggression.

The OXT rs6133010 variant modulates susceptibility to psychiatric symptoms during withdrawal in patients with alcohol dependence

BACKGROUND

Alcohol dependence (AD) confers susceptibility to distressing withdrawal symptoms that often lead to relapse. While neuroadaptation during withdrawal influences symptoms, the genetic factors behind it have not been thoroughly investigated. We utilized propensity score matching and investigated connections between AD, OXT rs6133010, and withdrawal symptoms to address confounding variables. By elucidating the OXT rs6133010-AD interaction, we aim to gain insights into alcohol withdrawal variability and contribute to personalized treatment approaches.

METHODS

A cross-sectional study design was employed involving a total of 389 AD patients and 184 healthy controls who were genotyped for the OXT rs6133010 polymorphism. Psychiatric symptoms were evaluated using standardized scales during early withdrawal. Propensity score matching mitigated age and education differences.

RESULTS

A two-way ANOVA demonstrated a significant AD x OXT rs6133010 interaction effect on hostility and anxiety. Further analysis revealed that the regulatory impact of OXT rs6133010 was exclusively in AD patients. Specifically, AD patients with the AA homozygote showed robust protection against hostility and anxiety. Path analysis unveiled the underlying mechanism of OXT symptom regulation.

CONCLUSION

This study presents novel evidence that OXT rs6133010 specifically modulates psychiatric symptoms in AD. The G allele may heighten hostility and anxiety vulnerability during alcohol withdrawal. These findings emphasize considering environmental factors when studying and utilizing oxytocin therapeutically. Additionally, OXT may not directly act as an anxiolytic but instead regulates anxiety by modulating hostility.

Neuropeptides affecting social behavior in mammals: Oxytocin

Oxytocin (OXT), a neuropeptide consisting of only nine amino acids, is synthesized in the paraventricular and supraoptic nuclei of the hypothalamus. Although OXT is best known for its role in lactation and parturition, recent research has shown that it also has a significant impact on social behaviors in mammals. However, a comprehensive review of this topic is still lacking. In this paper, we systematically reviewed the effects of OXT on social behavior in mammals. These effects of OXT from the perspective of five key behavioral dimensions were summarized: parental behavior, anxiety, aggression, attachment, and empathy. To date, researchers have agreed that OXT plays a positive regulatory role in a wide range of social behaviors, but there have been controversially reported results. In this review, we have provided a detailed panorama of the role of OXT in social behavior and, for the first time, delved into the underlying regulatory mechanisms, which may help better understand the multifaceted role of OXT. Levels of OXT in previous human studies were also summarized to provide insights for diagnosis of mental disorders.

A randomized controlled trial examining the effects of intranasal oxytocin on alcohol craving and intimate partner aggression among couples

BACKGROUND

While alcohol use disorder (AUD) is a well-established risk factor for intimate partner aggression (IPA), effective treatments for co-occurring AUD and IPA (AUD/IPA) are lacking. Oxytocin is one promising pharmacological candidate for AUD/IPA given its potential to modulate social behavior and attenuate alcohol use. However, emerging data suggests that oxytocin's prosocial effects are inconsistent, and a small number of studies have also found that oxytocin might have the potential to be aggressogenic. No studies have directly examined the impact of oxytocin on alcohol- or IPA-related outcomes in a dyadic context.

METHODS

The goal of this double-blind, randomized, and placebo-controlled trial was to examine the effects of a single dose of intranasal oxytocin (40 international units) on cue-induced alcohol craving, subjective aggression, laboratory task-based IPA, and cortisol reactivity in a sample of 100 couples (N = 200 individuals) with AUD and physical IPA in their current relationship.

RESULTS

There were no statistically significant differences between the oxytocin and placebo conditions for any of the primary outcomes.

CONCLUSIONS

Findings suggest that a single dose of intranasal oxytocin was not efficacious in mitigating alcohol craving or aggression in this sample. Although hypotheses were not supported, the findings provide important evidence that oxytocin was not aggressogenic in this high-risk sample. Future research investigating dispositional and contextual moderators of oxytocin response in addition to the therapeutic effects of more intensive oxytocin dosing or administration strategies on alcohol craving and aggression is warranted.

Reactive vs proactive aggression: A differential psychobiological profile? Conclusions derived from a systematic review

INTRODUCTION

Scholars have established subcategories of aggressive behavior in order to better understand this construct. Specifically, a classification based on motivational underpinnings makes it possible to differentiate between reactive and proactive aggression. Whereas reactive aggression is characterized by emotional lability, which means it is prone to impulsive reactions after provocation, proactive aggression is driven by low emotionality and high levels of instrumentality to obtain benefits. Some authors have conceived these two types as having a dichotomous nature, but others argue against this conceptualization, considering a complementary model more suitable. Hence, neuroscientific research might help to clarify discussions about their nature because biological markers do not present the same biases as psychological instruments.

AIM

The main objective of this study was to carry out a systematic review of studies that assess underlying biological markers (e.g., genes, brain, psychophysiological, and hormonal) of reactive and proactive aggression.

METHODS

To carry out this review, we followed PRISMA quality criteria for reviews, using five digital databases complemented by hand-searching.

RESULTS

The reading of 3993 abstracts led to the final inclusion of 157 papers that met all the inclusion criteria. The studies included allow us to conclude that heritability accounted for approximately 45% of the explained variance in both types of aggression, with 60% shared by both, especially, for overt and physical expression forms, and 10% specific to each type. Regarding allelic risk factors, whereas low functioning variants affecting serotonin transport and monoaminoxidase increased the risk of reactive aggression, high functioning variants were associated with proactive aggression. Furthermore, brain analysis revealed an overlap between the two types of aggression and alterations in the volume of the amygdala and temporal cortex. Moreover, high activation of the medial prefrontal cortex (PFC) facilitated proneness to both types of aggression equally. Whereas stimulation of the right ventrolateral (VLPFC) and dorsolateral (DLPFC) reduced proneness to aggression, inhibition of the left DLPFC increased it. Finally, psychophysiological and hormonal correlates in general did not clearly differentiate between the two types because they were equally related to each type (e.g., low basal cortisol and vagal variability in response to acute stress) CONCLUSIONS: This study reinforces the complementary model of both types of aggression instead of a dichotomous model. Additionally, this review also offers background about several treatments (i.e., pharmacological, non-invasive brain techniques…) to reduce aggression proneness.

Craving Moderates the Effects of Intranasal Oxytocin on Anger in Response to Social Stress Among Veterans With Co-Occurring Posttraumatic Stress Disorder and Alcohol Use Disorder

PURPOSE/BACKGROUND

Posttraumatic stress disorder (PTSD) and alcohol use disorder (AUD) commonly co-occur among US military veterans. Oxytocin may have therapeutic value in treating both conditions. The potential for oxytocin to augment affective features common to PTSD and AUD, such as anger, is relevant to inform emerging treatments.

METHODS/PROCEDURES

We examined the influence of intranasally administered oxytocin on connections between alcohol craving and stress-induced anger in a sample of 73 veterans (91.3% men) with co-occurring PTSD and AUD. Participants self-administered oxytocin (40 IU) or placebo (saline) 45 minutes before completing the Trier Social Stress Task (TSST). Self-reports of alcohol craving and anger were assessed pre- and post-TSST using a modified visual analog scale. Multiple regression analysis, including main effects for group, baseline craving, and their interaction, was used to predict post-TSST anger.

FINDINGS/RESULTS

A marginally significant interaction was observed, suggesting a positive association between baseline craving and anger for those in the oxytocin group (B = 0.65, P = 0.01). Among those reporting low craving, participants in the oxytocin group reported significantly lower post-TSST anger than those in the placebo group.

IMPLICATIONS/CONCLUSIONS

The current study is among the first to examine relevant psychosocial moderators that may influence the effects of oxytocin among veterans with comorbid PTSD and AUD. Although oxytocin attenuated ratings of anger after a stress task among those with low baseline craving, findings suggest that oxytocin may not be as effective at reducing anger, a highly salient factor in PTSD, for individuals experiencing high levels of craving. Findings are consistent with the social salience hypothesis and suggest that individual differences in alcohol craving should be considered when evaluating oxytocin as a potential treatment for individuals with comorbid PTSD and AUD.

Oxytocin and vasopressin within the ventral and dorsal lateral septum modulate aggression in female rats

In contrast to male rats, aggression in virgin female rats has been rarely studied. Here, we established a rat model of enhanced aggression in females using a combination of social isolation and aggression-training to specifically investigate the involvement of the oxytocin (OXT) and arginine vasopressin (AVP) systems within the lateral septum (LS). Using neuropharmacological, optogenetic, chemogenetic as well as microdialysis approaches, we revealed that enhanced OXT release within the ventral LS (vLS), combined with reduced AVP release within the dorsal LS (dLS), is required for aggression in female rats. Accordingly, increased activity of putative OXT receptor-positive neurons in the vLS, and decreased activity of putative AVP receptor-positive neurons in the dLS, are likely to underly aggression in female rats. Finally, in vitro activation of OXT receptors in the vLS increased tonic GABAergic inhibition of dLS neurons. Overall, our data suggest a model showing that septal release of OXT and AVP differentially affects aggression in females by modulating the inhibitory tone within LS sub-networks.

Infection threat shapes our social instincts

We social animals must balance the need to avoid infections with the need to interact with conspecifics. To that end we have evolved, alongside our physiological immune system, a suite of behaviors devised to deal with potentially contagious individuals. Focusing mostly on humans, the current review describes the design and biological innards of this behavioral immune system, laying out how infection threat shapes sociality and sociality shapes infection threat. The paper shows how the danger of contagion is detected and posted to the brain; how it affects individuals’ mate choice and sex life; why it strengthens ties within groups but severs those between them, leading to hostility toward anyone who looks, smells, or behaves unusually; and how it permeates the foundation of our moral and political views. This system was already in place when agriculture and animal domestication set off a massive increase in our population density, personal connections, and interaction with other species, amplifying enormously the spread of disease. Alas, pandemics such as COVID-19 not only are a disaster for public health, but, by rousing millions of behavioral immune systems, could prove a threat to harmonious cohabitation too.

Touching the social robot PARO reduces pain perception and salivary oxytocin levels

Human-human social touch improves mood and alleviates pain. No studies have so far tested the effect of human-robot emotional touch on experimentally induced pain ratings, on mood and on oxytocin levels in healthy young adults. Here, we assessed the effect of touching the robot PARO on pain perception, on mood and on salivary oxytocin levels, in 83 young adults. We measured their perceived pain, happiness state, and salivary oxytocin. For the 63 participants in the PARO group, pain was assessed in three conditions: Baseline, Touch (touching PARO) and No-Touch (PARO present). The control group (20 participants) underwent the same measurements without ever encountering PARO. There was a decrease in pain ratings and in oxytocin levels and an increase in happiness ratings compared to baseline only in the PARO group. The Touch condition yielded a larger decrease in pain ratings compared to No-Touch. These effects correlated with the participants' positive perceptions of the interaction with PARO. Participants with higher perceived ability to communicate with PARO experienced a greater hypoalgesic effect when touching PARO. We show that human-robot social touch is effective in reducing pain ratings, improving mood and - surprisingly - reducing salivary oxytocin levels in adults.

A Novel Role of CD38 and Oxytocin as Tandem Molecular Moderators of Human Social Behavior

Oxytocin is an important modulator of human affiliative behaviors, including social skills, human pair bonding, and friendship. CD38 will be discussed as an immune marker and then in more detail the mechanisms of CD38 on releasing brain oxytocin. Mention is made of the paralogue of oxytocin, vasopressin, that has often overlapping and complementary functions with oxytocin on social behavior. Curiously, vasopressin does not require CD38 to be released from the brain. This review discusses the social salience hypothesis of oxytocin action, a novel view of how this molecule influences much of human social behaviors often in contradictory ways. The oxytocinergic-vasopressinergic systems are crucial modulators of broad aspects of human personality. Of special interest are studies of these two hormones in trust related behavior observed using behavioral economic games. This review also covers the role of oxytocin in parenting and parental attachment. In conclusion, the effects of oxytocin on human behavior depend on the individual's social context and importantly as well, the individual's cultural milieu, viz. East and West. ACRONYMS: ACC = Anterior Cingulate ADP = Adenosine diphosphate AQ = Autism Quotient cADPR = Cyclic ADP-ribose CNS = Central nervous system DA = Dopamine eQTLC = Expression Quantitative Trait Loci LC-NE = Locus Coeruleus-Norepinephrine MRI = Magnetic Resonance Imaging OFC = Orbitofrontal cortices OXT = Oxytocin RAGE = Receptor for advanced glycation end-products SARM1 = Sterile Alpha and toll/interleukin-1 receptor motif-containing 1 TRPM2= Transient Receptor Potential Cation Channel Subfamily M Member 2 AVP = Vasopressin.

Intranasal oxytocin reduces reactive aggression in men but not in women: A computational approach

Aggression is an important behaviour that concerns individual survival and large-scale social stability. It comprises a variety of psychological subcomponents and is modulated by different biological factors. Two factors in particular, gender and oxytocin, appear to play a robust role in aggressive behaviour. However, whether these two factors interact to impact aggressive behaviour is not currently known. The current study investigated the modulating effect of gender on the relationship between oxytocin and aggression and characterized its underlying mechanisms by combining behavioural economic, pharmacological, and computational approaches. Specifically, we employed a double-blind, randomized, placebo-controlled, between-subjects design, in which one hundred participants (50 men and 50 women) completed a norm-training version of the multi-round one-shot ultimatum game (UG) after intranasal oxytocin or placebo administration. Rejection rates in the UG were adopted as an indicator of reactive aggression. The results indicated that oxytocin compared with placebo administration decreased aggression among men but not among women. Further analyses suggested that this decrease in aggression was a result of changes in men's sensitivity to provocation and positive affect, rather than norm adaptation rates or concerns about the cost of aggression. These findings highlight the role of gender in the relationship between oxytocin and reactive aggression and reveal its underlying psychological and computational mechanisms.

Impact of Oxytocin on the neural correlates of fearful face processing in PTSD related to childhood Trauma

Background: Posttraumatic stress disorder (PTSD) related to exposure to abuse and neglect during childhood is associated with particularly severe and persistent deleterious outcomes. Amygdala hyperreactivity has been observed in childhood trauma survivors and implicated in symptoms of PTSD. Objective: The neuropeptide oxytocin holds promise as a potential treatment for PTSD due to its ability to attenuate amygdala response to threat cues. However, the effect of oxytocin on amygdala reactivity in individuals with childhood trauma-related PTSD has not been investigated. Method: We employed a double-blind, randomized, placebo-controlled crossover design to examine the effects of intranasal oxytocin (24 IU) versus placebo on amygdala reactivity to fearful faces among childhood-trauma exposed individuals with PTSD (n = 17) and without PTSD (control group; n = 16). Results: Region-of-interest based amygdala fMRI signal magnitude did not differ by group, drug, or group x drug interaction. Self-report of childhood trauma exposure severity was negatively associated with the oxytocin-related change in left amygdala response in the PTSD group, but not in the control group. Supplementary and exploratory whole-brain analyses conducted separately in each group revealed that left amygdala reactivity to fearful faces was absent on placebo but increased on oxytocin in the control group. The PTSD group showed right amygdala activation to fearful faces in both the oxytocin and placebo conditions, but the left amygdala response observed in the placebo condition was diminished on oxytocin. Conclusions: Findings extend the literature pertaining to the potential for oxytocin to attenuate neural correlates of PTSD to a childhood trauma-related PTSD sample.

Where is the love? A double-blind, randomized study of the effects of intranasal oxytocin on stress regulation and aggression

Previous studies reveal that oxytocin (OT) encourages prosocial behavior in humans; however, animal studies and recent work in humans suggest that OT may also play a role in aggressive behavior and feelings. The present study investigated these competing predictions in the context of a competitive task among 85 healthy human participants (males and females). Using a randomized double-blind design, participants were assigned to an experimental (intranasal OT) or control (intranasal placebo) group. Hostility (Aggression Questionnaire) was measured at home (T1) and in the lab after intranasal administration (T2). Behavioral aggression was assessed post-intranasal administration. There was a significant difference between the OT and the placebo group on hostility scores (p = 0.03) and a significant time by group interaction for behavioral aggression (p < 0.05). Self-reported hostility was significantly higher at T2 compared to T1 (p < 0.001) among participants in the oxytocin group while no significant change was found in hostility among the placebo group. Behavioral aggression was slightly higher in the OT group (compared to the placebo group) directly after OT administration, however, the opposite relationship was found as the study period progressed. Both hostility and behavioral aggression findings were consistent across gender.