Brain areas affected by intranasal oxytocin show higher oxytocin receptor expression

Oxytocin pathway gene variation and corticostriatal resting-state functional connectivity

Genetic variations in single nucleotide polymorphisms (SNPs) within oxytocin pathway genes have been linked to social behavior and neurodevelopmental conditions. However, the neurobiological mechanisms underlying these associations remain elusive. In this study, we investigated the relationship between variations of 10 SNPs in oxytocin pathway genes and resting-state functional connectivity among 55 independent components using a large sample from the UK Biobank (N ≈ 30,000). Our findings revealed that individuals with the GG genotype at rs4813627 within the oxytocin structural gene (OXT) exhibited weaker resting-state functional connectivity in the corticostriatal circuit compared to those with the GA/AA genotypes. Empirical evidence has linked the GG genotype at OXT rs4813627 with a behavioral tendency of insensitivity to others. These results inform the neural mechanisms by which oxytocin-related genetic factors can influence social behavior.

Age-dependent effects of oxytocin in brain regions enriched with oxytocin receptors

Although intranasal oxytocin administration to tap into central functions is the most commonly used non-invasive means for exploring oxytocin's role in human cognition and behavior, the way by which intranasal oxytocin acts on the brain is not yet fully understood. Recent research suggests that brain regions densely populated with oxytocin receptors may play a central role in intranasal oxytocin's action mechanisms in the brain. In particular, intranasal oxytocin may act directly on (subcortical) regions rich in oxytocin receptors via binding to these receptors while only indirectly affecting other (cortical) regions via their neural connections to oxytocin receptor-enriched regions. Aligned with this notion, the current study adopted a novel approach to test 1) whether the connections between oxytocin receptor-enriched regions (i.e., the thalamus, pallidum, caudate nucleus, putamen, and olfactory bulbs) and other regions in the brain were responsive to intranasal oxytocin administration, and 2) whether oxytocin-induced effects varied as a function of age. Forty-six young (24.96 ± 3.06 years) and 44 older (69.89 ± 2.99 years) participants were randomized, in a double-blind procedure, to self-administer either intranasal oxytocin or placebo before resting-state fMRI. Results supported age-dependency in the effects of intranasal oxytocin administration on connectivity between oxytocin receptor-enriched regions and other regions in the brain. Specifically, compared to placebo, oxytocin decreased both connectivity density and connectivity strength of the thalamus for young participants while it increased connectivity density and connectivity strength of the caudate for older participants. These findings inform the mechanisms underlying the effects of exogenous oxytocin on brain function and highlight the importance of age in these processes.

Transcriptional and cell type profiles of cortical brain regions showing ultradian cortisol rhythm dependent responses to emotional face stimulation

The characteristic endogenous circadian rhythm of plasma glucocorticoid concentrations is made up from an underlying ultradian pulsatile secretory pattern. Recent evidence has indicated that this ultradian cortisol pulsatility is crucial for normal emotional response in man. In this study, we investigate the anatomical transcriptional and cell type signature of brain regions sensitive to a loss of ultradian rhythmicity in the context of emotional processing. We combine human cell type and transcriptomic atlas data of high spatial resolution with functional magnetic resonance imaging (fMRI) data. We show that the loss of cortisol ultradian rhythm alters emotional processing response in cortical brain areas that are characterized by transcriptional and cellular profiles of GABAergic function. We find that two previously identified key components of rapid non-genomic GC signaling - the ANXA1 gene and retrograde endocannabinoid signaling - show most significant differential expression (q = 3.99e-10) and enrichment (fold enrichment = 5.56, q = 9.09e-4). Our results further indicate that specific cell types, including a specific NPY-expressing GABAergic neuronal cell type, and specific G protein signaling cascades underly the cerebral effects of a loss of ultradian cortisol rhythm. Our results provide a biological mechanistic underpinning of our fMRI findings, indicating specific cell types and cascades as a target for manipulation in future experimental studies.

Oxytocin moderates corticolimbic social stress reactivity in cocaine use disorder and healthy controls

Social stress can contribute to the development of substance use disorders (SUDs) and increase the likelihood of relapse. Oxytocin (OT) is a potential pharmacotherapy that may buffer the effects of social stress on arousal and reward neurocircuitry. However, more research is needed to understand how OT moderates the brain’s response to social stress in SUDs. The present study examined the effect of intransasal OT (24 IU) versus placebo (PBO) on corticolimbic functional connectivity associated with acute social stress in individuals with cocaine use disorder (CUD; n = 67) and healthy controls (HC; n = 52). Psychophysiological interaction modeling used the left and right amygdala as seed regions with the left and right orbitofrontal and anterior cingulate cortex as a priori regions of interest. Moderators of the OT response included childhood trauma history and biological sex, which were examined in independent analyses. The main finding was that OT normalized corticolimbic connectivity (left amygdala-orbitofrontal and left amygdala-anterior cingulate) as a function of childhood trauma such that connectivity was different between trauma-present and trauma-absent groups on PBO, but not between trauma groups on OT. Effects of OT on corticolimbic connectivity were not different as a function of diagnosis (CUD vs HC) or sex. However, OT reduced subjective anxiety during social stress for CUD participants who reported childhood trauma compared to PBO and normalized craving response as a function of sex in CUD. The present findings add to some prior findings of normalizing effects of OT on corticolimbic circuitry in individuals with trauma histories and provide some initial support that OT can normalize subjective anxiety and craving in CUD.

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Social stress-related corticolimbic connectivity was affected by childhood trauma under placebo.

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Under oxytocin, corticolimbic connectivity differences due to childhood trauma were absent.

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Oxytocin reduced subjective anxiety in cocaine users with childhood trauma.

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Oxytocin reduced subjective craving in male cocaine users.

Effects of Intranasal Administration of Oxytocin and Vasopressin on Social Cognition and Potential Routes and Mechanisms of Action

Acute and chronic administration of intranasal oxytocin and vasopressin have been extensively utilized in both animal models and human preclinical and clinical studies over the last few decades to modulate various aspects of social cognition and their underlying neural mechanisms, although effects are not always consistent. The use of an intranasal route of administration is largely driven by evidence that it permits neuropeptides to penetrate directly into the brain by circumventing the blood-brain barrier, which has been considered relatively impermeable to them. However, this interpretation has been the subject of considerable debate. In this review, we will focus on research in both animal models and humans, which investigates the different potential routes via which these intranasally administered neuropeptides may be producing their various effects on social cognition. We will also consider the contribution of different methods of intranasal application and additionally the importance of dose magnitude and frequency for influencing G protein-coupled receptor signaling and subsequent functional outcomes. Overall, we conclude that while some functional effects of intranasal oxytocin and vasopressin in the domain of social cognition may result from direct penetration into the brain following intranasal administration, others may be contributed by the neuropeptides either entering the peripheral circulation and crossing the blood-brain barrier and/or producing vagal stimulation via peripheral receptors. Furthermore, to complicate matters, functional effects via these routes may differ, and both dose magnitude and frequency can produce very different functional outcomes and therefore need to be optimized to produce desired effects.

Oxytocin inhibits hindpaw hyperalgesia induced by orofacial inflammation combined with stress

Oxytocin (OT) is recognized as a critical neuropeptide in pain-related disorders. Chronic pain caused by the comorbidity of temporomandibular disorder (TMD) and fibromyalgia syndrome (FMS) is common, but whether OT plays an analgesic role in the comorbidity of TMD and FMS is unknown. Female rats with masseter muscle inflammation combined with 3-day forced swim (FS) stress developed somatic hypersensitivity, which modeled the comorbidity of TMD and FMS. Using this model, the effects of spinal OT administration on mechanical allodynia and thermal hyperalgesia in hindpaws were examined. Furthermore, the protein levels of OT receptors and 5-HT2A receptors in the L4-L5 spinal dorsal horn were analyzed by Western blot. The OT receptor antagonist atosiban and 5-HT2A receptor antagonist ritanserin were intrathecally injected prior to OT injection in the separate groups. Intrathecal injection of 0.125 μg and 0.5 μg OT attenuated the hindpaw hyperalgesia. The expression of OT receptors and 5-HT2A receptors in the L4-L5 spinal dorsal horn significantly increased following intrathecal injection of 0.5 μg OT. Intrathecal administration of either the OT receptor antagonist atosiban or 5-HT2A receptor antagonist ritanserin blocked the analgesic effect of OT. These results suggest that OT may inhibit hindpaw hyperalgesia evoked by orofacial inflammation combined with stress through OT receptors and/or 5-HT2A receptors, thus providing a therapeutic prospect for drugs targeting the OT system and for patients with comorbidity of TMD and FMS.