Inhibitory influence of oxytocin infusion on contingent negative variation and some memory tasks in normal men

Overview of Human Oxytocin Research

Social dysfunction is a core symptom of many psychiatric disorders and current medications have little or no remedial effects on this. Following on from extensive studies on animal models demonstrating that the neuropeptide oxytocin plays an important role in social recognition and bonding, human-based research has explored its therapeutic potential for social dysfunction in psychiatric disorders. Here we outline the historical background of this human-based research and some of the current methodological challenges it is facing. To date, research has primarily attempted to establish functional effects through measuring altered endogenous concentrations, observing effects of exogenous administration and by investigating the effects of polymorphisms and epigenetic modifications of the oxytocin receptor gene. We summarize some of the key findings on behavioral and neural effects that have been reported in healthy subjects in the context of social cognition which have provided encouragement that oxytocin could represent a promising therapeutic target. At the same time, we have identified a number of key areas where we urgently need further information about optimal dosing strategies and interactions with other peptide and transmitter systems. Finally, we have summarized current translational findings, particularly in the context of therapeutic outcomes of intranasal oxytocin administration in autism and schizophrenia. These clinical findings while somewhat varied in outcome do offer increasing cause for optimism that targeting the oxytocin system may provide a successful therapeutic approach for social dysfunction. However, future research needs to focus on the most effective treatment strategy and which types of individuals are likely to benefit most.

Positive emotion inducement modulates cardiovascular responses caused by mental work

Background

Positive emotion is considered as an important factor related to health-relevant biological processes, including cardiovascular responses. To explore the possibility of using positive emotion as a tool to manage cardiovascular response of white-collar workers, we examined the influence on cardiovascular response of positive emotion inducement before a mental work.

Method

Seventeen healthy males participated and performed a 10-min, PC-based Stroop color word task as their mental work. Before the task, 60 pleasant pictures chosen from the International Affective Picture System were presented in a random order under a positive emotion inducement condition while a gray screen was presented under a control condition. A 30-min relaxation period after completing the task was provided to examine the aftereffects of positive emotion inducement. Throughout these periods, systolic and diastolic blood pressure, mean arterial blood pressure, heart rate, stroke volume, cardiac output, and total peripheral resistance were measured continuously.

Results

Blood pressure and total peripheral resistance were lower during the picture presentation period under the positive emotion inducement period compared to the control condition. All indices did not differ during the color word task period. During the relaxation period after the task, however, blood pressure and total peripheral resistance were lower under the positive emotion inducement condition compared to the control condition.

Conclusion

Positive emotion inducement before a mental work beneficially modulates cardiovascular responses, suggesting that positive emotion inducement may be a useful tool to manage the cardiovascular response to mental work.

Opposing effects of oxytocin on overt compliance and lasting changes to memory

From infancy we learn to comply with societal norms. However, overt compliance is not necessarily accompanied by a change in internal beliefs. The neuromodulatory processes underlying these different phenomena are not yet understood. Here, we test the role of oxytocin in controlling overt compliance versus internalization of information delivered by a social source. After intranasal oxytocin administration, participants showed enhanced compliance to the erroneous opinion of others. However, this expression was coupled with a decrease in the influence of others on long-term memories. Our data suggest that this dissociation may result from reduced conflict in the face of social pressure, which increases immediate conforming behavior, but reduces processing required for deep encoding. These findings reveal a neurobiological control system that oppositely affects internalization and overt compliance.

Foster mother-infant bonding: associations between foster mothers' oxytocin production, electrophysiological brain activity, feelings of commitment, and caregiving quality

This study examined the biological processes associated with foster mother-infant bonding. In an examination of foster mother-infant dyads (N = 41, mean infant age = 8.5 months), foster mothers' oxytocin production was associated with their expressions of behavioral delight toward their foster infant and their average P3 response to images of all infant faces in the first 2 months of the relationship. Three months later, foster mothers' oxytocin production was still associated with delight toward their foster infant and was also specifically associated with their P3 response to an image of their foster infant. Similar to biologically related mothers and infants, oxytocin appears to be associated with foster mothers' brain activity and caregiving behavior, with patterns suggestive of bond formation.

Prosocial effects of oxytocin and clinical evidence for its therapeutic potential

There has been unprecedented interest in the prosocial effects of the neuropeptide oxytocin in humans over the last decade. A range of studies has demonstrated correlations between basal oxytocin levels and the strength of social and bonding behaviors both in healthy individuals and in those suffering from psychiatric disorders. Mounting evidence suggests associations between polymorphisms in the oxytocin receptor gene and prosocial behaviors and there may also be important epigenetic effects. Many studies have now reported a plethora of prosocial effects of intranasal application of oxytocin, including the domains of trust, generosity, socially reinforced learning, and emotional empathy. The main focus of this review will be to summarize human preclinical work and particularly the rapidly growing number of clinical studies which have identified important links between oxytocin and a wide range of psychiatric disorders, and have now started to directly assess its therapeutic potential.

A psychobiological rationale for oxytocin in the treatment of posttraumatic stress disorder

Although cognitive-behavioral therapy (CBT) is an effective treatment for posttraumatic stress disorder (PTSD), many patients fail to attain remission with CBT. The authors propose augmentation of CBT with oxytocin in the treatment of PTSD. Oxytocin has a combination of pharmacologic effects that result in a "sense of safety" for the patient, which is a prerequisite to successful treatment of PTSD. We suggest a dual explanatory mechanism as to why oxytocin may be effective: through a reduction of fear response (decreasing amygdala activation, inhibiting fear response, and enhancing extinction learning) and through an increase of social interaction (activating social reward-related brain regions increasing engagement in the therapeutic alliance). Given that PTSD is marked by deficits in anxiety/stress regulation and in social functioning, and that oxytocin is implicated in both of these areas, oxytocin seems a likely candidate for treatment of patients with PTSD. Further clinical studies of the therapeutic value of oxytocin are indicated.

The peptide that binds: a systematic review of oxytocin and its prosocial effects in humans

Oxytocin is a neuropeptide involved in a wide variety of social behaviors in diverse species. Recent research on its effects in humans has generated an arresting picture of its role in the dynamic function of the social brain. This review presents a broad overview of this uniquely social peptide, with a particular focus on extant studies of its effects in humans. After a short discussion of the evolutionary history of the oxytocin system, critical aspects of its peripheral and central physiology, and several salient technical issues surrounding human oxytocin research, a systematic review of studies of the effects of intranasal oxytocin in humans is presented. These effects include alterations in social decision making, processing of social stimuli, certain uniquely social behaviors (e.g., eye contact), and social memory. Oxytocin's prosocial influence is then framed by an evolutionary perspective on its role in mammalian social bonding and attachment. Finally, limitations in current human oxytocin research and oxytocin's potential therapeutic applications are discussed. Key conclusions are (1) human research with intranasal oxytocin has uniquely enhanced our understanding of the microstructure and function of the human social brain, and (2) the oxytocin system is a promising target for therapeutic interventions in a variety of conditions, especially those characterized by anxiety and aberrations in social function.

Oxytocin enhances processing of positive versus negative emotional information in healthy male volunteers

Animal studies have shown the role of oxytocin in affiliation and attachment, and recent evidence suggests that oxytocin is also involved in human models of approach behaviour, possibly by modulating the processing of emotionally valenced stimuli. Although oxytocin administration has been reported to decrease neural responses to facial emotional information, the effects on a wider range of behavioural measures of emotional processing shown to be sensitive to antidepressant manipulation have not been examined. The aim of this study was to investigate whether intranasally administered oxytocin affects the processing of positive and negative affective information in healthy male volunteers across tasks measuring attention, perception and memory. Twenty-nine male healthy volunteers were randomly allocated to receive a single dose of oxytocin nasal spray (24 UI) or placebo. 50 min later, participants completed a battery of psychological tests measuring emotional processing. A single dose of intranasally administered oxytocin slowed reaction time to correctly identify fearful facial expressions and reduced the misclassification of positive emotions as negative ones. These effects occurred in the absence of significant differences in subjective ratings of mood and anxiety. These results suggest that oxytocin modulates emotion processing in healthy male volunteers. This action may contribute to the emerging role of the neuropeptide in promoting affiliative and approach behaviours by reducing the salience of potentially ambiguous and threatening social stimuli.

Post-learning intranasal oxytocin modulates human memory for facial identity

The nanopeptide oxytocin has physiological functions during labour and lactation. In addition, oxytocin is known to modulate aggression, anxiety, social behaviour and cognition. Little is known about its effects on memory for emotional stimuli. In the present single-blind, placebo-controlled, randomised study we have investigated the short- and long-term effects of a single post-learning dose (20 IU) of intranasal oxytocin on memory for facial identity and expression in 36 healthy young females and males using a face portrait recognition test. In the acquisition phase of the test, 60 different male faces with happy, angry or neutral expressions were presented to the volunteers. Thirty minutes and 24h after oxytocin administration, recognition memory tests were performed using portraits with neutral facial expressions, only. Oxytocin improved identity recognition memory independently of participant's gender, for neutral and angry faces, whereas this effect was not present for happy faces. Oxytocin-treated subjects had a lower bias to judge not previously seen faces as being previously seen. Oxytocin had no effect on facial expression memory. In conclusion, oxytocin has distinct effects on memory performance for facial identity and may contribute to the modulation of social behaviour.

Oxytocin increases retention of social cognition in autism

BACKGROUND

Oxytocin dysfunction might contribute to the development of social deficits in autism, a core symptom domain and potential target for intervention. This study explored the effect of intravenous oxytocin administration on the retention of social information in autism.

METHODS

Oxytocin and placebo challenges were administered to 15 adult subjects diagnosed with autism or Asperger's disorder, and comprehension of affective speech (happy, indifferent, angry, and sad) in neutral content sentences was tested.

RESULTS

All subjects showed improvements in affective speech comprehension from pre- to post-infusion; however, whereas those who received placebo first tended to revert to baseline after a delay, those who received oxytocin first retained the ability to accurately assign emotional significance to speech intonation on the speech comprehension task.

CONCLUSIONS

These results are consistent with studies linking oxytocin to social recognition in rodents as well as studies linking oxytocin to prosocial behavior in humans and suggest that oxytocin might facilitate social information processing in those with autism. These findings also provide preliminary support for the use of oxytocin in the treatment of autism.

Postorgasmic illness syndrome: two cases

We describe the symptoms of a postejaculatory syndrome in two men with spontaneous ejaculations. The syndrome consists of severe fatigue, intense warmth, and a flulike state, with generalized myalgia. These symptoms occur rapidly after ejaculation and only disappear after 4 to 7 days. The symptoms are so severe that sexual activity is avoided. The cluster of symptoms is named postorgasmic illness syndrome (POIS). To date, no explanation has been offered for the etiology and pathogenesis of the symptoms, and the prevalence is unknown. Both cases are presented to draw attention to this syndrome for further research regarding etiology, pathogenesis, and treatment.

Inhibitory effect of oxytocin on corticotrope function in humans: are vasopressin and oxytocin ying-yang neurohormones?

Oxytocin (OT) and vasopressin (VP) are very similar neurohypophyseal peptides. While VP is known as an ACTH stimulating factor synergistic to CRF since two decades, the inhibiting activity of OT, first demonstrated in the human, is now confirmed in various species including mouse and rat!It is likely that endogenous oxytocinergic system which can be activated by physiological and/or pharmacological manipulation can "buffer" the stress activated vasopressin-ACTH-cortisol action. Since VP and OT share also opposite action on cognitive function, those two "sister" neuropeptides might be considered as "ago-antagonist" or "ying-yang" neurohormones!

Neurohypophyseal peptides and psychiatric diseases

The study of neurohypophyseal function in various neuropsychiatric diseases is interesting because: (1) The main neurohypophyseal peptides vasopressin (AVP) and oxytocin (OT) share by themselves modulatory influence on behavior. (2) Hypothalamo-posterior pituitary axis is directly influenced by modifications of central neurotransmitter metabolism involved in behavior control.

Behavioral effects of neurohypophyseal peptides in healthy volunteers: 10 years of research

A short summary of behavioral studies on the effects of vasopressin and oxytocin published during the past decade is provided. Only studies using healthy volunteers as subjects were included. Among the studies reviewed, large differences exist with respect to design, procedure, treatment schedule and dose used. Results from the majority of the studies support that vasopressin and oxytocin affect central nervous functions in man after systemic administration. Since the hormonal influences do not appear to be consistently restricted to certain stages of stimulus processing but nonspecifically concern a great variety of cognitive functions, it is suggested that the influence of hypophyseal peptides on stimulus processing is mediated through an action on basic mechanisms involved in the general regulation of central nervous activation, i.e., on arousal systems that could also alter affective aspects of stimulus processing. The altogether moderate number of studies, so far, does not provide a sufficient data base justifying a clinical application of these peptides as nootropic treatments.

Temporary peripartal impairment in memory and attention and its possible relation to oxytocin concentration

The aim of the present study was to investigate peripartal performance on cognitive tests and its possible relationship with plasma oxytocin concentrations. Twenty women (cases) were tested on five experimental occasions, the first toward the end of pregnancy and the last 12 months postpartum. On each experimental occasion performance on cognitive tests of memory and attention was recorded and oxytocin concentrations were simultaneously assayed in plasma-samples. Twenty non-pregnant women (controls) were investigated at similar intervals. Cases were found to have improved their performance on some cognitive tests significantly more than controls when results at 6 and 12 months after delivery were compared with those from the end of pregnancy and up to three months after partus. This observation strongly suggests impairment in cognitive performance during the peripartal period. Cases had significantly higher oxytocin concentrations than controls in plasma samples up to three months post partum. No correlation was, however, found between cognitive test results and levels of oxytocin concentration.

Treatment outcome, seizure duration, and the neurophysin response to ECT

Serum concentrations of immunoreactive neurophysin (IRN) and vasopressin-associated neurophysin (hNpI) were measured before and after the first treatment in a course of electroencephalographically monitored electroconvulsive therapy (ECT) given to 19 depressed patients. The difference (DIFF) between the serum concentrations of IRN and hNpI is equivalent to the concentration of oxytocin-associated neurophysin. Before ECT the six patients who had a good outcome at 2 months after the course of ECT had a mean serum IRN concentration one-half (p less than 0.05) and a mean serum DIFF concentration one-third (p less than 0.05) that of the 13 patients who had a poor outcome. The increase in serum DIFF concentration (but not IRN or hNpI) after the first ECT correlated with the improvement on the Hamilton Rating Scale for Depression (r = -0.73, p less than 0.005) and the Montgomery and Asberg Depression Rating Scale (r = -0.49, p less than 0.05). The peak percentage increase in serum DIFF concentrations after ECT was 4 times greater (p less than 0.001) in the good outcome group than in the poor outcome group. None of the neurophysin responses to ECT correlated with electroencephalogram-measured seizure duration.

[Modifications of contingent negative variation (CNV) induced by oxytocin infusion]

The central effects of an intravenous infusion of oxytocin (OT), 3,680 mIU in 45 min, were investigated in 20 male volunteers in a double-blind study combining an electrophysiological and a psychometrical approach. The electrophysiological approach consisted in the simultaneous recording of the CNV (Fz-A1 and Cz-A1) and the spontaneous EEG (bipolar P3-P4) recording on which was carried out an FFT analysis. On the other hand, various psychometric tests allowed to assess memory (Rey's tests), attention (K-T test) processes and mood changes (visual analogue scales). Within the hour following the infusion, OT induced a significant decrease of CNV amplitude and an increase of the post-imperative positive component at Cz-A1. A similar effect was still observed one week later, but was more marked at Fz-A1. Neither mood nor attention tests evidenced any significant effect of OT. Only one item of the memory test PRM (item 4) revealed a significant impairment after OT infusion. There were no subjective effects reported. These observations provide new electrophysiological arguments supporting a central action of peripheral OT administration in man. This action, which may be characterized as an acceleration of CNV "habituation" is the opposite of the one described with vasopressin.