Oxytocin promotes social grooming in bonobos: testing the biobehavioural feedback loop hypothesis

Oxytocin has attracted research attention due to its role in promoting social bonding. One notable recent hypothesis is the biobehavioral feedback loop, which posits that the oxytocin system has evolved to support the formation and maintenance of social bonds through a positive feedback loop, where oxytocin promotes social behaviours which then cause oxytocin release themselves. In the two Pan species, humans’ closest relatives, oxytocin is known to be released following key behaviours related to social bonding, such as social grooming in chimpanzees and female-female sexual behaviour in bonobos. However, no experimental evidence has demonstrated that oxytocin promotes such socio-positive behaviours. To test this, we administered nebulized oxytocin or saline placebo to a group of female bonobos and subsequently observed the change in their gross behavior during free interaction. We found that bonobos groomed other group members significantly more frequently in the oxytocin compared to placebo condition. Other behavioural measures did not largely differ between conditions, except for a nonsignificant trend for reduction in abnormal regurgitation/reingestion behaviour. Overall, we found that oxytocin promoted socio-positive interaction in bonobos, providing support for the biobehavioural feedback loop hypothesis of oxytocin in bonobo social evolution.

Effects of mammae hand massages on oxytocin release, milk yield, and milk quality in dairy cows

<p class="MDPI17abstract"><strong>Objective: </strong><span lang="EN-GB">The objective of this study was conducted to evaluate the effects of Mammae Hand Massages (MHM) on oxytocin release, milk yield, and milk quality in dairy cows.</span></p><p class="MDPI17abstract"><strong>Methods: </strong><span lang="EN">Twelve dairy cows with the following criterion: 5-yr-old, 1st to 9th month of lactation, and average body weight of 390 ± 5.55 kg were used. Cows were assigned in a randomized block design with 4 treatments, i.e T0 (without massage), T1 (MHM for 20 s), T2 (MHM for 50 s), and T3 (MHM for 80 s). Oxytocin release, milk yield, and milk quality were measured accordingly</span><span lang="EN-GB">.</span><strong></strong></p><p class="MDPI17abstract"><strong>Results: </strong><span lang="EN">The data obtained were analyzed using analysis of variance (ANOVA). The results showed that MHM had a very significant effect on milk production (P &lt;0.01) as evidenced by the MHM 50 s treatment obtained the highest average milk production (13.08 ± 3.38 liters/head/day) compared to the MHM 20 s, MHM 80 s and control. MHM (1-1.6 volts) for 50 s resulted in the highest release of oxytocin (0.22955 pcg/0.1mL) at 240 seconds compared to control, MHM 20 s and 80 s. Likewise, the percentage of milk protein content (2.96 ± 0.03) and milk fat content (4.27 ± 0.70) was highest at MHM 50 s</span><span lang="EN-GB">.</span><strong></strong></p><strong><span>Conclusions: </span></strong><span lang="EN">It can be concluded that MHM (1-1.6 volts) for 50 seconds increases the release of oxytocin, milk production, and milk quality in terms of the percentage of milk protein and fat content</span><span lang="EN-GB">.</span>

Transcutaneous auricular vagus nerve stimulation increases eye-gaze on salient facial features and oxytocin release

Background: Transcutaneous auricular vagus nerve stimulation (taVNS) is a non-invasive neuromodulation technique with promising therapeutic potential in the context of epilepsy, pain, and depression and which may also have beneficial effects on social cognition. However, the underlying mechanisms of taVNS are unclear and evidence regarding its role in social cognition improvement is limited. Objective: In order to investigate the impact of taVNS on social cognition we have studied its effects on gaze towards emotional faces using an eye-tracking task and also on release of the neuropeptide oxytocin which plays a key role in influencing social cognition and motivation. Methods: A total of fifty-four subjects were enrolled in a sham-controlled, participant-blind crossover experiment, consisting of two treatment sessions, separated by one week. In one session participants received 30-min taVNS (tragus), and in the other, they received 30-min sham (earlobe) stimulation with the treatment order counterbalanced across participants. Gaze duration towards the faces and facial features (eyes, nose, and mouth) were measured together with resting pupil size. Additionally, saliva samples were taken for the measurement of oxytocin concentrations by enzyme-linked immunoassay. Results: Saliva oxytocin concentrations increased significantly after taVNS compared to sham stimulation, while resting pupil size did not. In addition, taVNS increased fixation time on the nose region irrespective of face emotion, and this was positively correlated with increased saliva oxytocin concentrations. Conclusion: Our findings suggest that taVNS biases visual attention towards socially salient facial features across different emotions and this is associated with its effects on increasing endogenous oxytocin release.

Life experience rather than domestication accounts for dogs’ increased oxytocin release during social contact with humans

Dogs’ increased human-directed sociability compared to wolves may be the result of increased oxytocin system activity and decreased stress responses, but comparative studies accounting for life experience are lacking. We compared hand-raised, pack-living wolves’ and dogs’ behavior and hormone concentrations after interacting with a closely bonded and a familiar human. Both preferred the bonded partner, but dogs showed less variability in human-directed sociability than wolves. Physical contact was not associated with oxytocin but correlated positively with glucocorticoids in the pack-living animals when the human was not bonded. To clarify the role of life experience, we tested pet dogs and found that oxytocin concentrations correlated positively with physical contact with their owners, while glucocorticoids remained unaffected. Results show that, given similar experiences, wolf-dog differences in human-directed sociability and associated hormones are subtle and indicate that factors related to life as a pet dog rather than domestication account for oxytocin release during human–dog interactions.

Role of the 5-HT2A Receptor in Acute Effects of LSD on Empathy and Circulating Oxytocin

The psychedelic lysergic acid diethylamide (LSD) has experienced a revival in research, including clinical trials that evaluate LSD-assisted psychotherapy. LSD induces perceptual alterations and influences emotion processing in ways that may support psychotherapy. Here, we investigated the effects of LSD on emotional empathy and mediating role of the serotonin 5-hydroxytryptamine-2A (5-HT2A) receptor by administering 25, 50, 100, and 200 µg LSD alone and 200 µg LSD combined with pretreatment with the 5-HT2A receptor antagonist ketanserin (40 mg) using a placebo-controlled, double-blind, random-order, crossover design in 16 healthy subjects. The Multifaceted Empathy Test (MET) was used to assess the effects of LSD on emotional empathy. Plasma oxytocin levels were also measured. LSD dose-dependently increased implicit and explicit emotional empathy, with the highest 200 µg LSD dose having a significant effect compared with placebo. The 200 µg dose of LSD also moderately increased plasma oxytocin levels compared with placebo. Ketanserin reduced the LSD-induced elevations of oxytocin but not the LSD-induced increases in emotional empathy. These findings confirm that LSD enhances empathy, and this effect may be partially independent of its primary action on 5-HT2A receptors to induce subjective psychedelic effects. In contrast, LSD-induced oxytocin release may depend on 5-HT2A receptor stimulation, which is consistent with the psychedelic effect of LSD. Further studies are needed to investigate whether LSD may also enhance empathy and potentially produce therapeutic effects in patients who have deficits in empathy and impairments in social functioning.

Dendritic osmosensors modulate activity-induced calcium influx in oxytocinergic magnocellular neurons of the mouse PVN

Hypothalamic oxytocinergic magnocellular neurons have a fascinating ability to release peptide from both their axon terminals and from their dendrites. Existing data indicates that the relationship between somatic activity and dendritic release is not constant, but the mechanisms through which this relationship can be modulated are not completely understood. Here we use a combination of electrical and optical recording techniques to quantify activity-induced calcium influx in proximal vs. distal dendrites of oxytocinergic magnocellular neurons located in the paraventricular nucleus of the hypothalamus (OT-MCNs). Results reveal that the dendrites of OT-MCNs are weak conductors of somatic voltage changes, however activity-induced dendritic calcium influx can be robustly regulated by both osmosensitive and non-osmosensitive ion channels located along the dendritic membrane. Overall, this study reveals that dendritic conductivity is a dynamic and endogenously regulated feature of OT-MCNs that is likely to have substantial functional impact on central oxytocin release.

Affective Regulation Through Touch: Homeostatic and Allostatic Mechanisms

We focus on social touch as a paradigmatic case of a unifying perspective on the embodied, cognitive and metacognitive processes involved in social, affective regulation. Social touch appears to have three interrelated but distinct functions in affective regulation. First, it regulates affects by fulfilling embodied expectations about social proximity and attachment, mostly likely by convergent hedonic, dopaminergic and analgesic, opioidergic pathways. Second, caregiving touch such as feeding or warming an infant regulates affect by socially enacting homeostatic control and co-regulation of physiological states, most likely by corresponding ‘calming’ autonomic and endocrine pathways. Third, affective touch such as gentle stroking, kissing or tickling regulates affect by allostatic regulation of the salience and epistemic gain of particular experiences in given contexts and timescales, possibly regulated by oxytocin release and related ‘salience’ neuromodulators and circuits.

Neural circuitry for maternal oxytocin release induced by infant cries

SummaryOxytocin is a neuropeptide important for maternal physiology and childcare, including parturition and milk ejection during nursing. Suckling triggers oxytocin release, but other sensory cues- specifically infant cries- can elevate oxytocin levels in new human mothers, indicating that cries can activate hypothalamic oxytocin neurons. Here we describe a neural circuit routing auditory information about infant vocalizations to the oxytocin system of the mouse brain. We performed in vivo electrophysiological recordings and photometry from identified oxytocin neurons in awake maternal mice presented with pup calls. We found that oxytocin neurons responded to pup vocalizations via input from the posterior intralaminar thalamus, and repetitive thalamic stimulation induced lasting disinhibition of oxytocin neurons. Suppression of this pathway impaired maternal behavior and playing pup calls led to central oxytocin release in vivo. This circuit provides a mechanism for transforming acoustic input into hormonal output to ensure modulation of brain state required for successful parenting.

Increased oxytocin release precedes hyponatremia after pituitary surgery

Purpose The syndrome of inappropriate secretion of antidiuretic hormone (SIADH) is a well-known complication of transsphenoidal pituitary surgery, related to inappropriate secretion of arginine vasopressin (AVP). Its diagnosis is based on hyponatremia, with a peak of occurrence around day 7 after surgery and, to date, no early marker has been reported. In particular, copeptin levels are not predictive of hyponatremia in this case. Oxytocin (OXT) is secreted into the peripheral blood by axon terminals adjacent to those of AVP neurons in the posterior pituitary. Besides its role in childbirth and lactation, recent evidences suggested a role for OXT in sodium balance. The contribution of this hormone in the dysnatremias observed after pituitary surgery has however never been investigated. Methods We analyzed the urinary output of OXT in patients subjected to transsphenoidal pituitary surgery. Results While OXT excretion remained stable in patients who presented a normonatremic postoperative course, patients who were later diagnosed with SIADH-related hyponatremia presented with a significantly increased urinary secretion of OXT 4 days after surgery. Conclusion Taken together, these results show for the first time that urinary OXT output remains normally stable after transsphenoidal pituitary surgery. OXT excretion however becomes abnormally high on or around 4 days after surgery in patients later developing hyponatremia, suggesting that this abnormal dynamics of OXT secretion might serve as an early marker for transsphenoidal surgery-related hyponatremia attributed to SIADH.