Oxytocin and the modulation of pain experience: Implications for chronic pain management

Plasma pharmacokinetics of intravenous and intranasal oxytocin in nonpregnant adults

BACKGROUND

The development of oxytocin as a therapeutic agent outside of obstetrics has been hampered by antibody-based assays that lack specificity, leading to inconsistent and incompletely reported pharmacokinetic models to guide drug dosing. This study describes the population plasma pharmacokinetics of intravenous and intranasal oxytocin using a sensitive and specific liquid chromatography-tandem mass spectroscopy (LC/MS) assay.

METHODS

Two studies in healthy adult men and nonpregnant women were performed, the first with intravenous oxytocin 16.7 μg over 1 or 10 min and the second with intravenous oxytocin 13.7 μg over 30 min and, on a separate day, intranasal oxytocin 100 μg (n=24). Venous plasma oxytocin concentration was measured using LC/MS and enzyme-linked immunosorbent assay. Pharmacokinetic parameters were estimated using NONMEM.

RESULTS

The pharmacokinetics of intravenous oxytocin were well described by a two-compartment model (0% bias, 18% median inaccuracy). The two-compartment model for intranasal oxytocin was characterised by substantial subject-to-subject variability (9% median bias, 47% median inaccuracy). Nasal oxytocin bioavailability was 0.7%. Oxytocin samples assayed with LC/MS were systematically higher than simultaneous samples assayed with enzyme-linked immunosorbent assay.

CONCLUSIONS

The pharmacokinetics of intravenous oxytocin are well described by a two-compartment model. The low bioavailability (<1%) and large intersubject variability in plasma oxytocin after intranasal dosing could partially explain the inconsistent reports of oxytocin efficacy in the clinical literature with this delivery method. A publicly available simulator was created to guide oxytocin dosing in future studies.

CLINICAL TRIAL REGISTRATION

NCT03929367 (Study 1) and NCT05672667 (Study 2).

Discounting seems the most toxic dimension of invalidation in fibromyalgia: a cross-sectional analysis

Invalidation, both discounting (overt negative social responses) and lack of understanding (absence of positive social responses), is a common problem in fibromyalgia. The 'Fibromyalgia Imbalance of Threat and Soothing Systems' (FITSS) model indicates that different neuropsychological processes may underlie these two components of invalidation. Guided by this model, the aim of the current study was to clarify the differentiation between these two components of invalidation by examining their association with fibromyalgia severity, anxiety, and depression. This cross-sectional study included the Illness Invalidation Inventory (3*I), the Fibromyalgia Impact Questionnaire (FIQ), and the Hospital and Depression Scale (HADS). Demographics of the 280 respondents with fibromyalgia were: mean age 42.6 ± 11.8 yrs., 95% female, mean FIQ score 59.1 ± 15,5, possible or probable cases of anxiety and depression, 49% and 42%, respectively. Regression analyses revealed that discounting was associated with severity of fibromyalgia (t = 4.10, β = 0.34, p <.001), anxiety (t = 3.50, β = 0.29, p <.001) and depression (t = 3.64, β = 0.30, p <.001) symptoms. Neither lack of understanding (-1.62 ≤ t ≤.10, -0.13 ≤ β ≤ 0.01, p ≥ 0.11) nor the interaction of discounting and lack of understanding (-0.19 ≤ t ≤ 1.10, -0.01 ≤ β ≤ 0.07, p ≥ 0.27) was related to any of the outcome variables. The total model accounted for 8.8%, 5.3%, and 8.3% (adjusted R2) of variance in fibromyalgia severity, anxiety, and depression, respectively. In relation to both mental and physical health, discounting seems the most toxic dimension of invalidation in fibromyalgia. This suggests that overt negative responses should get attention in its management, especially in more severe fibromyalgia. Both people with fibromyalgia and people in their environment have a role in reducing invalidation.

The role of affective touch in mental illness: a systematic review of CT fiber dysregulation in psychological disorders and the therapeutic potential of CT fiber stimulation

Introduction

Over the past few decades, research on affective touch has clarified its impact on key psychological functions essential for environmental adaptation, such as self-awareness, self-other differentiation, attachment, and stress response. These effects are primarily driven by the stimulation of C-tactile (CT) fibers. Despite significant advancements in understanding the fundamental mechanisms of affective touch, its clinical applications in mental health remain underdeveloped. This systematic review aims to rigorously assess the scientific literature on the relationship between CT fiber stimulation and psychological disorders, evaluating its potential as a therapeutic intervention.

Methods

This systematic review was conducted in accordance with PRISMA guidelines. A search was performed in the EMBASE, PubMed, and Web of Science databases for articles published in the last 10 years. The review focused on two main aspects: (1) potential dysregulation of CT fibers in individuals with psychological disorders, and (2) psychological treatments based on CT fiber stimulation and their psychological and functional outcomes.

Results

Most studies investigating CT fiber dysregulation in psychological disorders reported sensory alterations, with patients rating affective touch as less pleasant than healthy controls. These differences were often associated with dysregulation in the reward network and interoceptive processing, with several studies suggesting reduced insular cortex activation as a contributing factor. Regarding psychological treatments, only a limited number of studies analyzed therapies based on CT fiber stimulation. Despite methodological variations and differences in psychological diagnoses, the available evidence suggests that affective touch therapies can effectively reduce symptom severity and improve interoception across different psychological conditions.

Discussion

The findings underscore the potential of affective touch as a therapeutic avenue for psychological disorders. However, given the dearth of studies on this topic, further analyses are necessary to fully understand its mechanisms and clinical efficacy. Expanding research in this area could provide valuable insights into functional impairments related to CT fiber dysregulation and support the development of targeted interventions for mental health treatment.

Different ways to reach the same goal: Are the analgesic effects of different types of tactile stimuli similar?

BACKGROUND

Tactile-induced analgesia (TIA) is a phenomenon in which different types of tactile stimulation alleviate pain via different mechanisms including empathy. As TIA plays an essential role in therapeutic situations and clinical conditions, it is crucial to determine whether specific tactile stimulations confer distinct benefits.

METHODS

Fifty-two subjects (31 females; 21-47 years) were exposed to four distinct experimental conditions involving three types of touch provided within a simulated supportive therapeutic setting. First, a contact heat (70 s) at a pain intensity of 60/100 Numerical Pain Scale (NPS) was applied to the forearm. The pain stimulus was then given simultaneously with vibration, gentle stroking, or handholding in random order. Pain ratings were reported at 5 and 65 s of each stimulation. Given the role of empathy in TIA, we also assessed the levels of empathy experienced by the subjects and the experimenter.

RESULTS

Handholding and vibration conditions were associated with a more rapid decrease in pain ratings compared to pain-alone (B values: handholding = -150.94 vs. pain-alone = -99.38, p = 0.01; vibration = -163.54 vs. pain-alone = -99.38, p < 0.001). Higher levels of the experimenter's empathy toward the subjects were associated with greater pain alleviation during vibration vs. pain-alone condition (B values: vibration = -56.42 vs. B pain-alone = -9.57, p = 0.04).

CONCLUSIONS

Vibration's potent analgesic effects may be attributed to its multi-channel analgesic mechanisms, including the therapist's empathy toward the participant. On the other hand, for handholding establishing an empathic interaction should be considered in a therapeutic setting to enhance its analgesic efficacy.

SIGNIFICANCE

This article explores the effectiveness of touch-based pain relief methods and their association with empathetic therapeutic interactions. The study emphasizes the significance of positive therapeutic interactions in facilitating tactile-induced analgesia.

Near-infrared spectroscopic study of blood flow changes in the dorsolateral prefrontal cortex during pain relief by odor stimulation

Chronic pain is an unpleasant experience caused by sensory and emotional instability, sometimes independent of actual tissue damage. Pain relief can greatly impact psychologic, social, and economic well-being. Aromatherapy has long been used to alleviate pain and previous studies demonstrated that odors alter cerebral blood flow. In the present study, we used near-infrared spectroscopy to test our hypothesis that olfactory stimulation contributes to pain relief by altering cerebral blood flow in brain regions associated with pain. Pain was induced by transcutaneous electrical stimulation and assessed using a visual analog scale. Peppermint and lavender olfactory stimuli were used. Based on previous results, we focused on the prefrontal cortex. A placebo experiment in which only air stimulation was presented revealed minimal changes in blood flow in the ventromedial prefrontal cortex when comparing pain stimulation alone and a combination of placebo and pain stimulation. We then examined changes in blood flow following the presentation of peppermint or lavender scents. Significant differences in blood flow were observed in the dorsolateral prefrontal cortex (DLPFC) between pain stimulation alone and pain stimulation combined with odor stimulation. These findings supported our previous finding that the DLPFC is involved in pain relief by patch-adhered stimulation, but odor stimulation activated the right DLPFC whereas patch-adhered stimulation suppressed the left DLPFC. One interpretation of the discrepancy is that the contrast of activation between the right and left DLPFC is important in pain relief. Our research will help to elucidate the neurologic mechanisms underlying pain relief.

Subcutaneous Oxytocin Injection Reduces Heat Pain: A Randomized-Controlled Trial

Oxytocin (OT) is a neuropeptide broadly implicated in social relationships and behavior. OT also exerts antinociceptive and pain-reducing effects in both humans and rodents. Recent research in rodents demonstrates that these effects can be peripheral and local. In human studies, intravenous OT has reduced visceral pain, and subcutaneous injection of OT has reduced postsurgical pain. However, the local effects of subcutaneous OT on experimental pain have not been studied. We conducted a 2-session crossover study during which healthy adults received a subcutaneous injection of synthetic OT (4 mcg/2 mL) or saline placebo (isotonic saline 2 mL), in a randomized and double-blinded manner. Eighteen participants completed full study procedures. We hypothesized that 10 minutes after injection, OT would reduce measures of acute mechanical pain, pressure pain, and heat pain perception. Subcutaneous OT significantly reduced ratings of heat pain intensity and unpleasantness (both P < .01), but did not alter mechanical pain, pressure pain, or heat pain threshold (all P > .05). Changes in heat pain were observed only on the injected arm and not on the contralateral arm, confirming a localized mechanism. These findings confirm the ability of OT in or near the skin to modulate nociceptive processes in cutaneous tissues in human adults, opening exciting avenues for further mechanistic research as well as potential clinical applications for acute pain. PERSPECTIVE: This randomized-controlled trial showed that a subcutaneous injection of OT could reduce perception of heat pain tested with a thermode. OT did not alter mechanical or pressure pain or thresholds for perceiving heat pain. These findings are relevant to scientists and clinicians seeking nonaddictive local drug treatments for pain.

Virtual reality-based analgesia: towards a novel framework for the biopsychosocial management of chronic pain

Virtual reality (VR) holds unmeasured potential as a multicomponent tool for managing chronic pain by adapting conventional in-person biopsychosocial pain management strategies into one virtual space. We review recent evidence showcasing the successful integration of cognitive behavioural therapy, mindfulness-based stress reduction, embodiment techniques, and physical therapy into VR environments, demonstrating positive outcomes in patients with chronic pain. We propose that future clinical and basic research build on this by integrating pain neuroscience techniques to help better understand pathophysiological pain mechanisms and treatment response. This could help facilitate early assessment and personalised treatment of chronic pain using a VR-based biopsychosocial approach.

COMT Variants are Associated With Breast and Nipple Pain

Estimates suggest that only 24.9% of infants born in 2019 were exclusively breastfed before 6 months of age, despite the known health benefits of exclusive breastfeeding. Breast and nipple pain is one of the primary determinants of exclusive breastfeeding. Environmental contributions to breastfeeding success have been reported extensively in the literature, but the contribution(s) of maternal genetics has yet to be discovered. The purpose of the study was to identify an association between pain and lactation-related gene variants with exclusive breastfeeding determinants. We selected 4 genes having single nucleotide polymorphisms (SNPs) with potential functional significance in breastfeeding and pain: prolactin receptor (PRLR), oxytocin receptor (OXTR), catechol-O-methyltransferase (COMT), and milk fat globule epidermal growth factor and factor V/VIII domain containing (MFGE8). We performed a cross-sectional secondary analysis of a longitudinal randomized controlled trial study, Promoting Self-Management of Breast and Nipple Pain with Biomarkers and Technology for Breastfeeding Women (NCT05262920). Breast and nipple pain, perceived insufficient milk, and breastfeeding self-efficacy were examined using total scale scores for the Brief Pain Inventory, Visual Analog Scale, H&H Lactation Scale, and the Breastfeeding Self-efficacy Scale-short form, respectively. Of the candidate genes examined, SNPs within COMT were significantly associated with breastfeeding-related outcomes. Specifically, COMT rs4633 and rs4680 minor allele carriers (T, A) reported higher breast and nipple pain intensity than women homozygous for the major allele (C, G). COMT is the most widely researched "pain gene" and has been linked to cold, postoperative, and postpartum pain. This study is the first to identify a contribution of COMT variants to breast and nipple pain and, as a result, to breastfeeding exclusivity. PERSPECTIVE: Two SNPs in the pain gene COMT are associated with breast and nipple pain. Clinically, a minor allele in COMT rs4633 and rs4680 may increase a woman's rating of moderate breast and nipple pain. TRIAL REGISTRATION: PROMPT was registered in ClinicalTrials.gov (protocol #NCT05262920).

An investigation on the role of oxytocin in chronic neuropathic pain in a Wistar rat model

Introduction Chemotherapy-induced peripheral neuropathy (CIPN) is a dose-limiting side effect with ineffective preventative and curative treatment. Currently, only Duloxetine has been recommended as effective treatment for CIPN, which has shown individual-dependent, short-term analgesic effects, with limiting adverse effects and poor bioavailability. The neuropeptide, oxytocin, may offer significant analgesic and anxiolytic potential, as it exerts central and peripheral attenuating effects on nociception. However, it is unknown whether the intervention administered in a model of CIPN is an effective therapeutic alternative or adjuvant. Materials and Methods The intervention was divided into two phases. Phase 1 aimed to induce CIPN in adult Wistar rats using the chemotherapeutic agent Paclitaxel. Mechanical (electronic von Frey filament) and thermal (acetone evaporation test and Hargreaves test) hypersensitivity testing were used to evaluate changes due to the neuropathic induction. Phase 2 consisted of a 14-day intervention period with saline (o.g.), duloextine (o.g.), or oxytocin (i.n.) administered as treatment. Following the intervention, anxiety-like behaviour was assessed using the elevated plus maze (EPM) and light-dark box protocols. Analysis of peripheral plasma corticosterone, peripheral plasma oxytocin, and hypothalamic oxytocin concentrations were assessed using ELISA assays. Results The findings showed that we were able to successfully establish a model of chemotherapy-induced peripheral neuropathy during Phase 1, determined by the increase in mechanical and thermal nociceptive responses following Paclitaxel administration. Furthermore, the animals treated with oxytocin displayed a significant improvement in mechanical sensitivity over the intervention phase, indicative of an improvement in nociceptive sensitivity in the presence of neuropathic pain. Animals that received Paclitaxel and treated with oxytocin also displayed significantly greater explorative behaviour during the EPM, indicative of a reduced presence of anxiety-like behaviour. Conclusion Our results support the hypothesis that intranasally administered oxytocin may augment the analgesic and anxiolytic effects of duloxetine in a chemotherapy induced peripheral neuropathy model in a Wistar rat. Future studies should consider administering the treatments in combination to observe the potential synergistic effects.

Boosting decision-making in rat models of early-life adversity with environmental enrichment and intranasal oxytocin

Impaired decision-making constitutes a fundamental issue in numerous psychiatric disorders. Extensive research has established that early life adversity (ELA) increases vulnerability to psychiatric disorders later in life. ELA in human neonates is associated with changes in cognitive, emotional, as well as reward-related processing. Maternal separation (MS) is an established animal model of ELA and has been shown to be associated with decision-making deficits. On the other hand, enriched environment (EE) and intranasal oxytocin (OT) administration have been demonstrated to have beneficial effects on decision-making in humans or animals. Given these considerations, our investigation sought to explore the impact of brief exposure to EE and intranasal OT administration on the decision-making abilities of adolescent rats that had experienced MS during infancy. The experimental protocol involved subjecting rat pups to the MS regimen for 180 min per day from postnatal day (PND) 1 to PND 21. Then, from PND 22 to PND 34, the rats were exposed to EE and/or received intranasal OT (2 μg/μl) for seven days. The assessment of decision-making abilities, using a rat gambling task (RGT), commenced during adolescence. Our findings revealed that MS led to impaired decision-making and a decreased percentage of advantageous choices. However, exposure to brief EE or intranasal OT administration mitigated the deficits induced by MS and improved the decision-making skills of maternally-separated rats. Furthermore, combination of these treatments did not yield additional benefits. These results suggest that EE and OT may hold promise as therapeutic interventions to enhance certain aspects of cognitive performance.

Oxytocin attenuates hypothalamic injury-induced cognitive dysfunction by inhibiting hippocampal ERK signaling and Aβ deposition

In clinical settings, tumor compression, trauma, surgical injury, and other types of injury can cause hypothalamic damage, resulting in various types of hypothalamic dysfunction. Impaired release of oxytocin can lead to cognitive impairment and affect prognosis and long-term quality of life after hypothalamic injury. Hypothalamic injury-induced cognitive dysfunction was detected in male animals. Behavioral parameters were measured to assess the characteristics of cognitive dysfunction induced by hypothalamic-pituitary stalk lesions. Brains were collected for high-throughput RNA sequencing and immunostaining to identify pathophysiological changes in hippocampal regions highly associated with cognitive function after injury to corresponding hypothalamic areas. Through transcriptomic analysis, we confirmed the loss of oxytocin neurons after hypothalamic injury and the reversal of hypothalamic-induced cognitive dysfunction after oxytocin supplementation. Furthermore, overactivation of the ERK signaling pathway and β-amyloid deposition in the hippocampal region after hypothalamic injury were observed, and cognitive function was restored after inhibition of ERK signaling pathway overactivation. Our findings suggest that cognitive dysfunction after hypothalamic injury may be caused by ERK hyperphosphorylation in the hippocampal region resulting from a decrease in the number of oxytocin neurons, which in turn causes β-amyloid deposition.

The psychophysiology of music-based interventions and the experience of pain

In modern times there is increasing acceptance that music-based interventions are useful aids in the clinical treatment of a range of neurological and psychiatric conditions, including helping to reduce the perception of pain. Indeed, the belief that music, whether listening or performing, can alter human pain experiences has a long history, dating back to the ancient Greeks, and its potential healing properties have long been appreciated by indigenous cultures around the world. The subjective experience of acute or chronic pain is complex, influenced by many intersecting physiological and psychological factors, and it is therefore to be expected that the impact of music therapy on the pain experience may vary from one situation to another, and from one person to another. Where pain persists and becomes chronic, aberrant central processing is a key feature associated with the ongoing pain experience. Nonetheless, beneficial effects of exposure to music on pain relief have been reported across a wide range of acute and chronic conditions, and it has been shown to be effective in neonates, children and adults. In this comprehensive review we examine the various neurochemical, physiological and psychological factors that underpin the impact of music on the pain experience, factors that potentially operate at many levels - the periphery, spinal cord, brainstem, limbic system and multiple areas of cerebral cortex. We discuss the extent to which these factors, individually or in combination, influence how music affects both the quality and intensity of pain, noting that there remains controversy about the respective roles that diverse central and peripheral processes play in this experience. Better understanding of the mechanisms that underlie music's impact on pain perception together with insights into central processing of pain should aid in developing more effective synergistic approaches when music therapy is combined with clinical treatments. The ubiquitous nature of music also facilitates application from the therapeutic environment into daily life, for ongoing individual and social benefit.

A Pilot Study of Urine Oxytocin as an Objective Biomarker for Chronic Pain

Background: Measuring pain objectively or quantitatively is difficult. Since urine oxytocin (OXT) concentration has been reported to be potentially associated with chronic pain. Purpose: We conducted a pilot study to evaluate the relationship between changes in numerical rating scale (NRS) score following nerve block and urine OXT concentration in patients with chronic pain. Methods: We investigated 19 chronic pain patients who were admitted to our hospital for nerve intervention. NRS score and urine OXT concentration were assessed before and after the nerve block. Results: NRS scores were 7 [6, 9] and 2 [1, 4] (median [interquartile range]) before and after the treatment intervention, respectively. Urinary OXT levels were 523 [293, 743] and 531 [308, 887] pg/mL (median [interquartile range]) before and after the treatment, respectively. We compared the group with greater improvement in NRS after the treatment intervention and those with less improvement. The group with greater improvement in NRS after the treatment intervention showed a greater increase in OXT level. However, baseline urine OXT concentrations were highly variable in patients with chronic pain and the changes in urinary OXT concentrations were also variable. Conclusion: Based on this pilot study, the utility of urine OXT concentration as an objective biomarker of chronic pain needs further investigation.

Oxytocin Modulation in Mindfulness-Based Pain Management for Chronic Pain

In the context of chronic pain management, opioid-based treatments have been heavily relied upon, raising concerns related to addiction and misuse. Non-pharmacological approaches, such as Mindfulness-Based Pain Management, offer alternative strategies. We conducted a mechanistic clinical study to investigate the impact of an 8-week Mindfulness-Based Pain Management intervention on chronic pain, the modulation of inflammatory markers, stress physiology, and oxytocin, and their interplay with clinical pain symptoms and perception, in comparison to a patient wait-list active control. A total of 65 participants, including 50 chronic pain patients and 15 healthy controls, underwent salivary assays to assess endocrine markers, oxytocin, interleukin (IL)-1b, IL-6, IL-8, tumor necrosis factor (TNF)-a, and dehydroepiandrosterone sulphate (DHEA-S). Psychological assessments were also conducted to evaluate aspects of pain perception, mindfulness, mood, and well-being. Findings revealed significant differences between chronic pain patients and healthy controls in various clinical metrics, highlighting the psychological distress experienced by patients. Following Mindfulness-Based Pain Management, oxytocin levels significantly increased in chronic pain patients, that was not observed in the patient wait-list control group. In contrast, cytokine and DHEA-S levels decreased (not to statistically significant margins) supporting anti-inflammatory effects of Mindfulness-Based Pain Management. The fact DHEA-S levels, a marker of stress, did attenuate but not to statistically meaningful levels, suggests that pain reduction was not solely related to stress reduction, and that oxytocin pathways may be more salient than previously considered. Psychological assessments demonstrated substantial improvements in pain perception and mood in the intervention group. These results contribute to the growing body of evidence regarding the effectiveness of mindfulness-based interventions in chronic pain management and underscore oxytocin's potential role as a therapeutic target.

The Roles of Endogenous Opioids in Placebo and Nocebo Effects: From Pain to Performance to Prozac

Placebo and nocebo effects have been well documented for nearly two centuries. However, research has only relatively recently begun to explicate the neurobiological underpinnings of these phenomena. Similarly, research on the broader social implications of placebo/nocebo effects, especially within healthcare delivery settings, is in a nascent stage. Biological and psychosocial outcomes of placebo/nocebo effects are of equal relevance. A common pathway for such outcomes is the endogenous opioid system. This chapter describes the history of placebo/nocebo in medicine; delineates the current state of the literature related to placebo/nocebo in relation to pain modulation; summarizes research findings related to human performance in sports and exercise; discusses the implications of placebo/nocebo effects among diverse patient populations; and describes placebo/nocebo influences in research related to psychopharmacology, including the relevance of endogenous opioids to new lines of research on antidepressant pharmacotherapies.

Interoceptive technologies for psychiatric interventions: From diagnosis to clinical applications

Interoception-the perception of internal bodily signals-has emerged as an area of interest due to its implications in emotion and the prevalence of dysfunctional interoceptive processes across psychopathological conditions. Despite the importance of interoception in cognitive neuroscience and psychiatry, its experimental manipulation remains technically challenging. This is due to the invasive nature of existing methods, the limitation of self-report and unimodal measures of interoception, and the absence of standardized approaches across disparate fields. This article integrates diverse research efforts from psychology, physiology, psychiatry, and engineering to address this oversight. Following a general introduction to the neurophysiology of interoception as hierarchical predictive processing, we review the existing paradigms for manipulating interoception (e.g., interoceptive modulation), their underlying mechanisms (e.g., interoceptive conditioning), and clinical applications (e.g., interoceptive exposure). We suggest a classification for interoceptive technologies and discuss their potential for diagnosing and treating mental health disorders. Despite promising results, considerable work is still needed to develop standardized, validated measures of interoceptive function across domains and before these technologies can translate safely and effectively to clinical settings.

Oxytocin increases itch sensitivity of mice in late pregnancy and its peripheral receptor mechanism of itch-promoting effect

Oxytocin (OXT) is secreted in a large amount during the middle and late pregnancy. Except for the regulation of functions related to childbirth, OXT is involved in the regulation of cognition, social behavior, addiction, pain and so on. Our aim is to confirm the increase of OXT content in mice in late pregnancy is the main cause of itch during pregnancy and observe whether exogenously administered OXT can induce or increase itch sensitivity. The research shows that itch sensitivity of mice increased significantly in late pregnancy and basically returned to normal one day after delivery. The number of OXT-positive neurons in paraventricular nucleus (PVN) and the content of OXT in serum of the late pregnant mice increased significantly, and decreased sharply after delivery. Intradermal injection of low concentration of OXT (0.2 nmol/L) could not induce scratching behavior in mice, but high concentration of OXT (5 nmol/L, 10 nmol/L) could do this in a dose-dependent manner. Low concentration of OXT significantly increased the itch sensitivity to histamine. Intradermal injection of oxytocin receptor (OXTR) or arginine vasopressin-1a receptor (AVPR1A) antagonist did not affect histamine-induced scratching behavior, but both reversed the increase of itch sensitivity in late pregnant mice or the facilitated itch sensitivity by OXT. Study suggests that both endogenous and exogenous increases in OXT can increase the body's sensitivity to itch, and even induce itch directly. Pruritus during pregnancy is closely related to the increase of OXT content in vivo. In the periphery, the itch-promoting effect of OXT is mediated by OXTR and AVPR1A.

Preliminary results from a randomized, controlled, cross-over trial of intrathecal oxytocin for neuropathic pain

OBJECTIVE

Compare intrathecal oxytocin, 100 µg to placebo on ongoing neuropathic pain and mechanical hyperalgesia and allodynia.

STUDY DESIGN

Randomized, controlled, double-blind cross-over.

SETTING

Clinical research unit.

SUBJECTS

Individuals aged 18 to 70 years with neuropathic pain for at least 6 months.

METHODS

Individuals received intrathecal injections of oxytocin and saline, separated by at least 7 days, and ongoing pain in neuropathic area (VAS [visual analog scale]) and areas of hypersensitivity to von Frey filament and cotton wisp brushing were measured for 4 hours. Primary outcome was VAS pain in the first 4 hours after injection, analyzed by linear mixed effects model. Secondary outcomes were verbal pain intensity scores at daily intervals for 7 days and areas of hypersensitivity and elicited pain for 4 hours after injections.

RESULTS

The study was stopped early after completion of 5 of 40 subjects planned due to slow recruitment and funding limitations. Pain intensity prior to injection was 4.75 ± 0.99 and modeled pain intensity decreased more after oxytocin than placebo to 1.61 ± 0.87 and 2.49 ± 0.87, respectively (P = .003). Daily pain scores were lower in the week following injection of oxytocin than saline (2.53 ± 0.89 vs 3.66 ± 0.89; P = .001). Allodynic area decreased by 11%, but hyperalgesic area increased by 18% after oxytocin compared to placebo. There were no study drug related adverse effects.

CONCLUSION

Although limited by the small number of subjects studied, oxytocin reduced pain more than placebo in all subjects. Further study of spinal oxytocin in this population is warranted.

TRIAL REGISTRATION

This study was registered at ClinicalTrials.gov on 03/27/2014 (NCT02100956). The first subject was studied on 06/25/2014.

Structure-Based Design of Glycosylated Oxytocin Analogues with Improved Selectivity and Antinociceptive Activity

Acute and chronic pain is often treated with opioids despite the negative side effects of constipation, physical dependence, respiratory depression, and overdose. The misuse of opioid analgesics has given rise to the opioid crisis/epidemic, and alternate nonaddictive analgesics are urgently needed. Oxytocin, a pituitary hormone, is an alternative to the small molecule treatments available and has been used as an analgesic as well as for the treatment and prevention of opioid use disorder (OUD). Clinical implementation is limited by its poor pharmacokinetic profile, a result of the labile disulfide bond between two cysteine residues in the native sequence. Stable brain penetrant oxytocin analogues have been synthesized by replacement of the disulfide bond with a stable lactam and glycosidation of the C-terminus. These analogues show exquisite selectivity for the oxytocin receptor and potent in vivo antinociception in mice following peripheral (i.v.) administration, supporting further study of their clinical potential.

Reconceptualizing Somatic Dysfunction in the Light of a Neuroaesthetic Enactive Paradigm

Background: Palpatory findings are considered a central element of osteopathic practice, especially when associated with a patient's altered regulative functions than with named somatic dysfunctions. Although osteopathic theories for somatic dysfunction could be plausible, the clinical applicability of the concept is debated, especially because it is largely related to simple cause-effect models of osteopathic care. In contrast to a linear kind of diagnosis of a "tissue as a producer of symptoms", this perspective article aims to provide a conceptual and operational framework in which the somatic dysfunction evaluation process is seen as a neuroaesthetic (en)active encounter between osteopath and patient. Subsections relevant to the subject: To summarize all concepts of the hypothesis, the enactive neuroaesthetics principles are proposed as a critical foundation for the osteopathic assessment and treatment of the person, specifically addressing a new paradigm for somatic dysfunction. Conclusions, and future directions: The present perspective article represents a proposition to blend technical rationality informed by neurocognitive and social sciences, and professional artistry clinical experience informed by traditional tenets, to overcome the controversy around somatic dysfunction, rather than dismissing the concept.

From Oxytocin to Compassion: The Saliency of Distress

Compassion is a warm response of care and concern for those who are suffering, which drives individuals to devote their resources for the sake of others. A prominent neuroevolutionary framework grounds compassion in the neurobiology of the mammalian caregiving system. Accordingly, it has been suggested that the oxytocinergic system, which plays a central role in parental caregiving and bonding, provides the neurobiological foundation for compassion towards strangers. Yet, the specific role of oxytocin in compassion is far from clear. The current paper aims to target this gap and offer a theoretical framework that integrates the state-of-the-art literature on oxytocin with research on compassion. We suggest that oxytocin mediates compassion by enhancing the saliency of cues of pain and distress and discuss the plausible underlying neurobiological substrates. We further demonstrate how the proposed framework can account for individual differences in compassion, focusing on the effects of attachment on caregiving and support. The proposed framework integrates the current scientific understanding of oxytocin function with compassion-related processes. It thus highlights the largely ignored attentional processes in compassion and taps into the vast variability of responses in social contexts involving pain and suffering.

Effects of intranasal oxytocin on pain perception among human subjects: A systematic literature review and meta-analysis

INTRODUCTION

Oxytocin (OXT) is a peptide hormone produced in the hypothalamus that plays a neuromodulatory role in emotion, stress, and anxiety. Due to its multidimensional role, OXT is a promising target for therapeutic interventions to treat pain.

OBJECTIVE

Perform a systematic literature review, followed by a meta-analysis to identify the effects of intranasal OXT on the self-perception of clinical and experimental pain among human subjects.

METHOD

A systematic review was conducted in the PubMed, PsycINFO, Scielo, Lilacs, and Web of Science databases, using the keywords Oxytocin, Pain, Analgesia, and Nociception.

RESULTS

Fifteen papers were included in the meta-analysis. None of the outcomes presented statistical significance in terms of the interventions' effect size: pain intensity (SMD = -0.02 (CI 95 %: -0.14 to 0.10; p = 0.76)) and pain unpleasantness (SMD = -0.15 (CI 95 %: -0.34 to 0.04; p = 0.12)). No meta-analysis was performed for pain threshold or tolerance because few papers address these outcomes.

CONCLUSION

There was no statistically significant effect of intranasal OXT administration on pain perception, considering equivalence limits between (-0.2 and 0.2). However, it must be considered that the study designs may not have been sensitive enough to detect minor analgesic effects of OXT, which, being weak, may also not be perceived at a conscious level. Additionally, OXT effects possibly depend on specific characteristics of the painful condition, such as pain complexity, intensity, and duration, contextual variables like the presence of social and affective support, and individual characteristics.

Emotion regulation and the salience network: a hypothetical integrative model of fibromyalgia

Fibromyalgia is characterized by widespread pain, fatigue, sleep disturbances and other symptoms, and has a substantial socioeconomic impact. Current biomedical and psychosocial treatments are unsatisfactory for many patients, and treatment progress has been hindered by the lack of a clear understanding of the pathogenesis of fibromyalgia. We present here a model of fibromyalgia that integrates current psychosocial and neurophysiological observations. We propose that an imbalance in emotion regulation, reflected by an overactive 'threat' system and underactive 'soothing' system, might keep the 'salience network' (also known as the midcingulo-insular network) in continuous alert mode, and this hyperactivation, in conjunction with other mechanisms, contributes to fibromyalgia. This proposed integrative model, which we term the Fibromyalgia: Imbalance of Threat and Soothing Systems (FITSS) model, should be viewed as a working hypothesis with limited supporting evidence available. We hope, however, that this model will shed new light on existing psychosocial and biological observations, and inspire future research to address the many gaps in our knowledge about fibromyalgia, ultimately stimulating the development of novel therapeutic interventions.

Effectiveness of early essential newborn care on breastfeeding and maternal outcomes: a nonrandomized controlled study

Background

Breastfeeding and maternal health play crucial roles in improving newborn health, which is closely related to the development of families and society. Early essential newborn care, which emphasizes early exclusive breastfeeding and skin-to-skin contact, is recommended by the World Health Organization. This study aimed to explore the association of early essential newborn care with breastfeeding and maternal outcomes.

Methods

A nonrandomized controlled study was carried out from May 2020 to January 2021 in a tertiary hospital in Chengdu city, China. Pregnant women were recruited from the maternity ward before they gave birth. Early essential newborn care was performed for 91 mother-newborn pairs after birth in the intervention group, while routine birth care was performed for 91 mother-newborn pairs in the control group. Data on breastfeeding and maternal outcomes were collected pre-test and post-test and were recorded by trained data collectors and retrieved from hospital case record files.

Results

Compared with the control group, the intervention group had a higher incidence of early breastfeeding initiation, an earlier initiation and longer duration for the first breastfeeding, a higher incidence of successful first breastfeeding, more exclusive breastfeeding at hospital discharge, higher maternal breastfeeding self-efficacy, a shorter duration of the third stage of labour, lower postpartum blood loss, and lower scores of maternal pain and anxiety postpartum; the differences were statistically significant (p < 0.05).

Conclusion

The implementation of high-quality early essential newborn care can help mothers initiate early breastfeeding, improve exclusive breastfeeding rates at hospital discharge, enhance breastfeeding self-efficacy, promote the woman’s recovery from labour, and reduce maternal anxiety and pain in the postpartum period. High-quality early essential newborn care is recommended to policymakers and medical professionals to improve breastfeeding and maternal outcomes.

Trial registration

Chinese Clinical Trial Registry, Retrospective Registration (27/7/2021), registration number: ChiCTR2100049231.

Elevated Neuropeptides in Dry Eye Disease and Their Clinical Correlations

PURPOSE

The goal of this study was to assess neuropeptide levels in patients with dry eye disease (DED) and investigate their correlations with clinical characteristics.

METHODS

This study included 38 eyes of 38 patients diagnosed with DED (DED group) and 38 eyes of 38 healthy volunteers without DED (control group). Ocular surface evaluation was performed. The severity of dry eye symptoms and signs in the DED group was graded. Neuropeptides [substance P (SP), alpha-melanocyte-stimulating hormone (α-MSH), β-endorphin, neurotensin, and oxytocin] and inflammatory cytokines levels were measured in basal tears. The link between neuropeptides and clinical parameters was investigated using Spearman rank correlation.

RESULTS

Overall, 76.3% of patients in the DED group showed dry eye symptoms and signs that were inconsistent in severity. Compared with the control group, the DED group showed higher levels of SP, α-MSH, and oxytocin in tears (P = 0.012, P = 0.030, and P = 0.006, respectively), but similar levels of β-endorphin and neurotensin (P = 0.269 and P = 0.052). The levels of SP, α-MSH, and oxytocin were elevated in DED patients with higher grading of symptoms than clinical signs (all P < 0.05). SP, α-MSH, and oxytocin levels in tears were positively correlated with Ocular Surface Disease Index scores, frequency of sensitivity to light, and frequency of blurred vision (all P < 0.05).

CONCLUSIONS

The increased tear levels of SP, α-MSH, and oxytocin may be linked to ocular discomfort in DED. Neuropeptides may play a key role in the development of DED, especially in DED patients with more severe symptoms than clinical signs.

Three-Day Continuous Oxytocin Infusion Attenuates Thermal and Mechanical Nociception by Rescuing Neuronal Chloride Homeostasis via Upregulation KCC2 Expression and Function

Oxytocin (OT) and its receptor are promising targets for the treatment and prevention of the neuropathic pain. In the present study, we compared the effects of a single and continuous intrathecal infusion of OT on nerve injury-induced neuropathic pain behaviours in mice and further explore the mechanisms underlying their analgesic properties. We found that three days of continuous intrathecal OT infusion alleviated subsequent pain behaviours for 14 days, whereas a single OT injection induced a transient analgesia for 30 min, suggesting that only continuous intrathecal OT attenuated the establishment and development of neuropathic pain behaviours. Supporting this behavioural finding, continuous intrathecal infusion, but not short-term incubation of OT, reversed the nerve injury-induced depolarizing shift in Cl- reversal potential via restoring the function and expression of spinal K+-Cl- cotransporter 2 (KCC2), which may be caused by OT-induced enhancement of GABA inhibitory transmission. This result suggests that only continuous use of OT may reverse the pathological changes caused by nerve injury, thereby mechanistically blocking the establishment and development of pain. These findings provide novel evidence relevant for advancing understanding of the effects of continuous OT administration on the pathophysiology of pain.

Estrogen can abolish oxytocin-induced spinal anti-hyperalgesia

Our previous study verified a sex difference of anti-hyperalgesia in rats and anti-allodynia in mice induced by intrathecal oxytocin (OT). In the model of intraplantar carrageenan-induced inflammatory hyperalgesia, intrathecal OT injection induced a substantial anti-hyperalgesia in male rats even at a low dose (0.125 nmol). In contrast, female rats only responded to an extremely high dose (1.25 nmol). This sex difference concurs with a lower expression of OT receptors and higher expression of insulin-regulated aminopeptidase (IRAP; OT degrading enzyme) in the spinal cords of female rats. In this study, we further determined the role of female hormones in this sex difference by using ovariectomized rats. Our results show that a low dose of intrathecal OT caused a significant anti-hyperalgesia effect in ovariectomized female rats, similar to that seen in male rats. Ovariectomy did not cause any change of paw edema except at the late stage of convalescence when compared with the sham-operated group. Ovariectomy-induced faster recovery from edema but did not affect the severity of hyperalgesia. Moreover, there was a similar amount of IRAP expression in ovariectomized and sham rats. When estradiol (E2) was given together with OT, OT-induced anti-hyperalgesia was abolished at the developmental stage of hyperalgesia in ovariectomized rats. These results show an inhibitory role of female hormones generated from ovaries (mainly estrogen) in the sex difference of anti-hyperalgesia induced by OT. This study suggests the feasibility of a novel OT-based remedy to treat hyperalgesia in men and in menopausal women no receiving hormonal supplements.

Dorsolateral prefrontal cortex sensing analgesia

Chronic pain often has an unknown cause, and many patients with chronic pain learn to accept that their pain is incurable and pharmacologic treatments are only temporarily effective. Complementary and integrative health approaches for pain are thus in high demand. One such approach is soft touch, e.g., adhesion of pyramidal thorn patches in a pain region. The effects of patch adhesion on pain relief have been confirmed in patients with various types of pain. A recent study using near-infrared spectroscopy revealed that the dorsolateral prefrontal cortex (DLPFC), especially the left side, is likely to be inactivated in patients experiencing pain relief during patch treatment. Mindfulness meditation is another well-known complementary and integrative approach for achieving pain relief. The relation between pain relief due to mindfulness meditation and changes in brain regions, including the DLPFC, has long been examined. In the present review article, we survey the literature describing the effects of the above-mentioned complementary and integrative treatments on pain relief, and outline the important brain regions, including the DLPFC, that are involved in analgesia. We hope that the present article will provide clues to researchers who hope to advance neurosensory treatments for pain relief without medication.

Oxytocin reduces romantic rejection-induced pain in online speed-dating as revealed by decreased frontal-midline theta oscillations

BACKGROUND

Romantic rejection is an emotionally distressful experience profoundly affecting life, possibly leading to mental illness or suicide. Oxytocin (OT) is a neuropeptide widely implicated in reducing physical pain and negative emotions; however, whether OT has an effect on reducing intense social pain (e.g., romantic rejection) remains unknown. Here, we tested the effect of OT on social pain and investigated its role in the outcome evaluation phase of social decision-making.

METHODS

Electroencephalographic recordings were obtained between August 2nd and October 20th, 2020 in Shenzhen University from 61 healthy participants in a double-blind, placebo-controlled study with a between-subject design. We defined frontal-midline theta oscillation as a neural signature of social pain and assessed self-reported pleasantness ratings for four possible romantic outcomes in an online speed-dating task.

RESULTS

In the placebo group, greater theta power was induced by romantic rejection, being associated with rejection distress. This pattern was not observed in the OT group, where romantic rejection induced significantly decreased theta power compared to the placebo group; in the OT group, there was no association between theta power and rejection distress. Furthermore, the frontal-midline theta oscillation could be source-localized to brain areas overlapping with the physical-social pain matrix (i.e., somatosensory cortex, anterior cingulate cortex, frontal pole, and supplementary motor area).

CONCLUSIONS

OT relieves social pain caused by romantic rejection, reflected in decreased frontal-midline theta oscillations and a diminished connection between theta power and rejection distress. These findings can help understand and harness OT's pain-reducing effect on social pain.

Evaluating the efficacy of intranasal oxytocin on pain and function among individuals who experience chronic pain: a protocol for a multisite, placebo-controlled, blinded, sequential, within-subjects crossover trial

INTRODUCTION

Current treatments for chronic pain (eg, opioids) can have adverse side effects and rarely result in resolution of pain. As such, there is a need for adjuvant analgesics that are non-addictive, have few adverse side effects and are effective for pain management across several chronic pain conditions. Oxytocin is a naturally occurring hormone that has gained attention for its potential analgesic properties. The objective of this trial is to evaluate the efficacy of intranasal oxytocin on pain and function among adults with chronic pain.

METHODS AND ANALYSIS

This is a placebo-controlled, triple-blind, sequential, within-subject crossover trial. Adults with chronic neuropathic, pelvic and musculoskeletal pain will be recruited from three Canadian provinces (British Columbia, Alberta and Newfoundland and Labrador, respectively). Enrolled patients will provide one saliva sample pretreatment to evaluate basal oxytocin levels and polymorphisms of the oxytocin receptor gene before being randomised to one of two trial arms. Patients will self-administer three different oxytocin nasal sprays twice daily for a period of 2 weeks (ie, 24 IU, 48 IU and placebo). Patients will complete daily diaries, including standardised measures on day 1, day 7 and day 14. Primary outcomes include pain and pain-related interference. Secondary outcomes include emotional function, sleep disturbance and global impression of change. Intention-to-treat analyses will be performed to evaluate whether improvement in pain and physical function will be observed posttreatment.

ETHICS AND DISSEMINATION

Trial protocols were approved by the Newfoundland and Labrador Health Research Ethics Board (HREB #20227), University of British Columbia Clinical Research Ethics Board (CREB #H20-00729), University of Calgary Conjoint Health Research Ethics Board (REB20 #0359) and Health Canada (Control # 252780). Results will be disseminated through publication in peer-reviewed journals and presentations at scientific conferences.

TRIAL REGISTRATION NUMBER

NCT04903002; Pre-results.

Maternal speech decreases pain scores and increases oxytocin levels in preterm infants during painful procedures

Preterm infants undergo early separation from parents and are exposed to frequent painful clinical procedures, with resultant short- and long-term effects on their neurodevelopment. We aimed to establish whether the mother's voice could provide an effective and safe analgesia for preterm infants and whether endogenous oxytocin (OXT) could be linked to pain modulation. Twenty preterm infants were exposed to three conditions-mother's live voice (speaking or singing) and standard care-in random order during a painful procedure. OXT levels (pg/mL) in saliva and plasma cortisol levels were quantified, and the Premature Infant Pain Profile (PIPP) was blindly coded by trained psychologists. During the mother's live voice, PIPP scores significantly decreased, with a concomitant increase in OXT levels over baseline. The effect on pain perception was marginally significant for singing. No effects on cortisol levels were found. The mother's live voice modulated preterm infants' pain indicators. Endogenous OXT released during vocal contact is a promising protective mechanism during early painful interventions in at-risk populations.

Pain relief associated with decreased oxyhemoglobin level in left dorsolateral prefrontal cortex

Pain in the elbow, shoulder, knee, lower back, and various other joints is relieved by adhesion of pyramidal thorn patches. To elucidate the pain relief mechanism induced by the patches, we established a quantitative method for estimating the pain reduction and investigated the brain regions that change in association with pain relief. We first attempted to quantify the pain relief using transcutaneous electric stimulation (TCES) and a visual analog scale (VAS), and then applied near-infrared spectroscopy (NIRS) to the prefrontal cortex, including the dorsolateral prefrontal cortex (DLPFC) and the orbitofrontal cortex (OFC). We also examined the salivary oxytocin levels, which are thought to reflect oxytocin secretion levels from the posterior pituitary in the brain. Application of pyramidal thorn patches to pain regions decreased the pain degree estimated using TCES and VAS. Oxyhemoglobin levels were likely to be decreased in the left DLPFC on the basis of NIRS measurements during patch treatment, suggesting that the left DLPFC is involved in pain relief. On the other hand, the salivary oxytocin levels varied widely. A potential reason for the varying salivary oxytocin levels is its utilization in the pain region as an analgesic agent. Our results suggest that the left DLPFC will become a target brain region for pain therapy.

Oxytocin and positive couple interaction affect the perception of wound pain in everyday life

A large body of animal and human laboratory research has linked social interaction and support to pain perception, with a possible role for the neuropeptide oxytocin as a neuroendocrine mediator. However so far, it has been unclear whether these effects translate to ecologically valid everyday life behavior and pain perception. In a randomized placebo-controlled study, a standard suction blister skin wound was induced to N = 80 romantic couples (N = 160 individuals). Couples then received intranasal oxytocin or placebo twice daily and were either instructed to perform a positive social interaction (partner appraisal task, PAT) once in the laboratory and two times during the following five days, or not. During these days, all participants reported their subjective pain levels multiple times a day using ecologically momentary assessment. Results from hierarchical linear modeling suggest that pain levels within the couples were inter-related. In men, but not in women, oxytocin reduced pain levels. Women reported lower pain levels in the group of positive social interaction, while this effect did not show in men. These results suggest that intranasal oxytocin might have sex-specific effects with pain reducing effects in men but the opposite effects in women. In contrast, especially women benefit from positive interaction in terms of dampened pain levels after positive interaction. The results add to the evidence for health-beneficial effects of positive couple interaction and point to underlying neuroendocrine mechanisms in everyday life pain specifically. The sex-specific effects, in particular, may have implications for psychopharmacological treatment of pain in men and women.

Intranasal oxytocin and the stress-buffering effects of social support during experimentally induced pain: The role of attachment security

BACKGROUND

This study examined whether intranasal oxytocin enhances the stress-buffering effects of social support during experimentally induced pain, taking into account the role of individual differences in attachment security.

METHODS

Female participants (N = 193) were randomly assigned to oxytocin (24 IU intranasal) or placebo and to receive support or no support from a friend (2 × 2 factorial design with repeated measures)). Participants underwent the Cold Pressor Task (CPT) and were monitored for heart rate variability (HRV: RMSSD) and heart rate and reported pain levels. The Experiences in Close Relationships Questionnaire was used to measure attachment.

RESULTS

Oxytocin reduced RMSSD (p = 0.003, partial ɳ² = 0.03) and increased heart rate (p = 0.039, partial ɳ² = 0.03) in individuals who received support, possibly reflecting an enhanced attentional state. Oxytocin did not enhance beneficial effects of social support on perceived pain, but increased pain intensity in avoidantly attached individuals who were supported by a friend (p = 0.009, partial ɳ² = 0.06).

LIMITATIONS

Only female participants were examined. Future studies are needed to determine sex differences in how oxytocin shapes stress-buffering effects of support.

CONCLUSIONS

Oxytocin may enhance the salience of social proximity and may be a mechanism underlying previously reported social influences on cardiovascular and mental health. However, oxytocin effects depend on interpersonal insecurities and may trigger discomfort in avoidantly attached individuals. Caution about oxytocin's therapeutic promise is warranted.

OXTR rs53576 Variation with Breast and Nipple Pain in Breastfeeding Women

BACKGROUND

Thirty percent of women who seek professional breastfeeding support require assistance with ongoing breast and nipple pain and < 50% of women report resolution of their pain. It is unknown if there is a molecular risk for ongoing breast and nipple pain during breastfeeding. Aim -To evaluate associations among breast and nipple pain sensitivity and candidate pain sensitivity single-nucleotide polymorphisms [SNPs], (COMT rs6269, rs4633, rs4818, rs4680 and OXTR rs2254298, rs53576) in breastfeeding women. Design - A secondary analysis of a pilot randomized controlled trial of a pain self-management intervention conducted over 6 weeks postpartum. Setting and Participants - Sixty women were recruited from two hospital settings after birth. Methods - All participants underwent standardized mechanical somatosensory testing for an assessment of pain sensitivity and provided baseline buccal swabs for genetic analysis. At 1, 2, and 6 weeks postpartum, women self-reported breast and nipple pain severity using a visual analogue scale. Results - Women with the minor allele OXTR rs53576 reported 8.18-fold higher breast and nipple pain severity over time. For every 1-unit increase in Mechanical detection threshold and windup ratio, women reported 16.51-fold and 4.82-fold higher breast and nipple pain severity respectively. Six women with the OXTR rs2254298 minor allele reported allodynia. Conclusion - The presence of OXTR alleles in women with enhanced pain sensitivity suggests a phenotype of genetic risk for ongoing breast and nipple with potential for pain-associated breastfeeding cessation. Somatosensory testing identified women who reported higher breast and nipple pain during the first weeks of breastfeeding.

Perception of integrative care in paediatric oncology-perspectives of parents and patients

PURPOSE

For some years now, a programme for the use of integrative care in paediatric oncology has been established in a German university hospital and offers patients and parents complementary treatment options. According to their medical condition and wishes. A variety of external applications such as medical wraps, warm oil compresses and rhythmic embrocations are offered. This article analyses how patients and parents perceived and experienced the integrative care program.

METHODS

In this qualitative study, data consists of field notes conducted through participant observation, informal conversations and interviews with parents (n = 25) during the implementation phase of the program. Data was analysed on basis of thematic analysis and organized with the analysis software MAXQDA.

RESULTS

Parents and families intuitively developed strategies for dealing with crisis situations such as childhood cancer. In addition, many of the families brought with them a wealth of experience in complementary medicine. Parents perceived the integrative care treatments as soothing, relaxing and pain-relieving for their child. Patients could relax and side effects of chemotherapy were alleviated. However, children, who undergoing chemotherapy were not always open for physical touch and thus sometimes also rejected the treatments sometimes.

CONCLUSION

The analysed integrative care programme is perceived as a strong patient and family-centred approach of support during the oncological paediatric treatment. From a salutogenetic viewpoint, this program aims to strengthen the dimension of manageability within the concept of sense of coherence. Parents are given supportive means to manage side effects and ease their child's suffering, through touch and attention that can be very beneficial.

Altered Interoceptive Perception and the Effects of Interoceptive Analgesia in Musculoskeletal, Primary, and Neuropathic Chronic Pain Conditions

Chronic pain (CP) severely disrupts the daily life of millions. Interoception (i.e., sensing the physiological condition of the body) plays a pivotal role in the aetiology and maintenance of CP. As pain is inherently an interoceptive signal, interoceptive frameworks provide important, but underutilized, approaches to this condition. Here we first investigated three facets of interoceptive perception in CP, compared with pain-free controls. We then introduce a novel interoceptive treatment and demonstrate its capacity to reduce pain severity in CP, potentially providing complementary analgesic treatments. Study 1 measured interoceptive accuracy, confidence and sensibility in patients (N = 60) with primary, secondary musculoskeletal, and neuropathic CP. Compared with matched controls, CP participants exhibited significantly lower interoceptive accuracy and interoceptive confidence. Pain severity was predicted positively by interoceptive accuracy, anxiety and depression, and negatively by interoceptive confidence. Study 2 tested a promising new interoceptive treatment for CP, in a single-blind between-subjects design (N = 51) with primary, secondary musculoskeletal, and neuropathic CP patients. The treatment specifically activates the C-Tactile system, by means of controlled stimulation of interoceptive unmyelinated afferents, at 3 cm/s with a force of 2.5 mN. This treatment led to significant pain reduction (mean 23%) in the CP treatment group after only 11 min, while CP controls who received comparable but non-interoceptive stimulation reported no change in pain intensity. These studies highlight the importance of interoceptive approaches to CP and demonstrate the potential of this novel method of C-Tactile stimulation to provide complementary analgesic treatments.

Oxytocin as a regulatory neuropeptide in the trigeminovascular system: Localization, expression and function of oxytocin and oxytocin receptors

BACKGROUND

Recent clinical findings suggest that oxytocin could be a novel treatment for migraine. However, little is known about the role of this neuropeptide/hormone and its receptor in the trigeminovascular pathway. Here we determine expression, localization, and function of oxytocin and oxytocin receptors in rat trigeminal ganglia and targets of peripheral (dura mater and cranial arteries) and central (trigeminal nucleus caudalis) afferents.

METHODS

The methods include immunohistochemistry, messenger RNA measurements, quantitative PCR, release of calcitonin gene-related peptide and myography of arterial segments.

RESULTS

Oxytocin receptor mRNA was expressed in rat trigeminal ganglia and the receptor protein was localized in numerous small to medium-sized neurons and thick axons characteristic of A∂ sensory fibers. Double immunohistochemistry revealed only a small number of neurons expressing both oxytocin receptors and calcitonin gene-related peptide. In contrast, double immunostaining showed expression of the calcitonin gene-related peptide receptor component receptor activity-modifying protein 1 and oxytocin receptors in 23% of the small cells and in 47% of the medium-sized cells. Oxytocin immunofluorescence was observed only in trigeminal ganglia satellite glial cells. Oxytocin mRNA was below detection limit in the trigeminal ganglia. The trigeminal nucleus caudalis expressed mRNA for both oxytocin and its receptor. K⁺-evoked calcitonin gene-related peptide release from either isolated trigeminal ganglia or dura mater and it was not significantly affected by oxytocin (10 µM). Oxytocin directly constricted cranial arteries ex vivo (pEC₅₀ ∼ 7); however, these effects were inhibited by the vasopressin V_1A antagonist SR49059.

CONCLUSION

Oxytocin receptors are extensively expressed throughout the rat trigeminovascular system and in particular in trigeminal ganglia A∂ neurons and fibers, but no functional oxytocin receptors were demonstrated in the dura and cranial arteries. Thus, circulating oxytocin may act on oxytocin receptors in the trigeminal ganglia to affect nociception transmission. These effects may help explain hormonal influences in migraine and offer a novel way for treatment.

Hypothalamic Neuropeptide Brain Protection: Focus on Oxytocin

Oxytocin (OXT) is hypothalamic neuropeptide synthetized in the brain by magnocellular and parvo cellular neurons of the paraventricular (PVN), supraoptic (SON) and accessory nuclei (AN) of the hypothalamus. OXT acts in the central and peripheral nervous systems via G-protein-coupled receptors. The classical physiological functions of OXT are uterine contractions, the milk ejection reflex during lactation, penile erection and sexual arousal, but recent studies have demonstrated that OXT may have anti-inflammatory and anti-oxidant properties and regulate immune and anti-inflammatory responses. In the pathogenesis of various neurodegenerative diseases, microglia are present in an active form and release high levels of pro-inflammatory cytokines and chemokines that are implicated in the process of neural injury. A promising treatment for neurodegenerative diseases involves new therapeutic approaches targeting activated microglia. Recent studies have reported that OXT exerts neuroprotective effects through the inhibition of production of pro-inflammatory mediators, and in the development of correct neural circuitry. The focus of this review is to attribute a new important role of OXT in neuroprotection through the microglia–OXT interaction of immature and adult brains. In addition, we analyzed the strategies that could enhance the delivery of OXT in the brain and amplify its positive effects.

Physical Pain as Pleasure: A Theoretical Perspective

Physical pain represents a common feature of Bondage and Discipline/Dominance and Submission/Sadism and Machochism (BDSM) activity. This article explores the literature accounting for how painful stimuli may be experienced as pleasurable among practitioners of BDSM, and contrasting this with how it is experienced as painful among non-BDSM individuals. We reviewed the available literature on pain and on BDSM, and used the findings to postulate a theory accounting for how painful stimuli are experienced as pleasurable. Our theory was then checked with BDSM practitioners. The emotional, physiological, and psychological elements of pain interact to facilitate the experience of pain as pleasure in BDSM. A multitude of interconnected factors was theorized to alter the experience of BDSM pain, including: neural networks, neurotransmitters, endogenous opioids and endocannabinoids, visual stimuli, environmental context, emotional state, volition and control, interpersonal connection, sexual arousal, and memories. The experience of pain in this context can bring about altered states of consciousness that may be similar to what occurs during mindfulness meditation. Through understanding the mechanisms by which pain may be experienced as pleasure, the role of pain in BDSM is demystified and, it is hoped, destigmatized.

Pain-modulating effects of oxytocin in patients with chronic low back pain

The neuropeptide oxytocin (OT) has been shown to play a modulatory role in nociception. However, analgesic effects of OT in chronic pain conditions remain elusive and the neural underpinnings have not yet been investigated in humans. Here, we conducted an exploratory, randomized, placebo-controlled, cross-over study to examine effects of intranasal OT in male patients suffering from chronic low back pain (CBP) versus healthy controls (HC). N = 22 participants with CBP and 22 HCs were scanned using functional magnetic resonance imaging (fMRI) while they continuously rated either spontaneously occurring back pain or acute thermal pain stimuli applied to the lower back. During heat pain processing we found that OT versus PL attenuated pain intensity ratings and increased BOLD responses in the caudate nucleus of the striatum in CBP versus HCs. Spontaneously experienced pain in contrast to heat pain was associated with activation changes in the medial frontal cortex (MFC) and the anterior cingulate cortex (ACC) as reported in previous studies. However, we did not observe OT effects on spontaneously experienced pain in CBP patients. Overall, our preliminary data may suggest that the striatum is a key structure underlying the pain-modulating effects of OT in patients with chronic pain and adds to the growing evidence linking the neuropeptide to pain modulation in humans. Further studies on neuronal OT effects in larger samples of chronic back pain patients are needed to understand probable mechanisms of OT effects in chronic pain. This article is part of the special issue on Neuropeptides.

Effects of route of administration on oxytocin-induced changes in regional cerebral blood flow in humans

Could nose-to-brain pathways mediate the effects of peptides such as oxytocin (OT) on brain physiology when delivered intranasally? We address this question by contrasting two methods of intranasal administration (a standard nasal spray, and a nebulizer expected to improve OT deposition in nasal areas putatively involved in direct nose-to-brain transport) to intravenous administration in terms of effects on regional cerebral blood flow during two hours post-dosing. We demonstrate that OT-induced decreases in amygdala perfusion, a key hub of the OT central circuitry, are explained entirely by OT increases in systemic circulation following both intranasal and intravenous OT administration. Yet we also provide robust evidence confirming the validity of the intranasal route to target specific brain regions. Our work has important translational implications and demonstrates the need to carefully consider the method of administration in our efforts to engage specific central oxytocinergic targets for the treatment of neuropsychiatric disorders.

Musculoskeletal Pain and Brain Morphology: Oxytocin's Potential as a Treatment for Chronic Pain in Aging

Chronic pain disproportionately affects older adults, severely impacting quality of life and independent living, with musculoskeletal pain most prevalent. Chronic musculoskeletal pain is associated with specific structural alterations in the brain and interindividual variability in brain structure is likely an important contributor to susceptibility for the development of chronic pain. However, understanding of age-related structural changes in the brain and their associations with chronic musculoskeletal pain is currently limited. Oxytocin (OT), a neuropeptide present in the periphery and central nervous system, has been implicated in pain attenuation. Variation of the endogenous OT system (e.g., OT receptor genotype, blood, saliva, and cerebrospinal fluid OT levels) is associated with morphology in brain regions involved in pain processing and modulation. Intranasal OT administration has been shown to attenuate pain. Yet, studies investigating the efficacy of OT for management of chronic musculoskeletal pain are lacking, including among older individuals who are particularly susceptible to the development of chronic musculoskeletal pain. The goal of this focused narrative review was to synthesize previously parallel lines of work on the relationships between chronic pain, brain morphology, and OT in the context of aging. Based on the existing evidence, we propose that research on the use of intranasal OT administration as an intervention for chronic pain in older adults is needed and constitutes a promising future direction for this field. The paper concludes with suggestions for future research in the emerging field, guided by our proposed Model of Oxytocin's Anagelsic and Brain Structural Effects in Aging.

Persistent pain after cesarean delivery

The incidence of persistent pain after cesarean deliveries (CD) varies but is much lower than after comparable surgeries. However, with over four million deliveries annually and a rising CD rate, even a low prevalence of persistent pain after CD impacts many otherwise healthy young women. Consideration of the pathophysiology of persistent pain after surgery and the risk factors predisposing women to persistent and chronic pain after CD provides insights into the prevention and treatment of persistent pain; and improves the quality of care and recovery after CD. The findings that the peripartum state and oxytocin confer protection against persistent pain may provide new and interesting perspectives for the prevention and treatment of chronic pain caused by trauma or surgery. Predictive tools available to identify and target patients at high risk of acute and chronic pain have mostly weak to modest predictive correlations and many are either not clinically feasible or too time-consuming to apply. Persistent pain has been linked to the severity of acute postoperative pain and opioid exposure. Modified surgical techniques, neuraxial anesthesia and opioid-sparing analgesia may help limit the development of persistent and chronic pain. The goal of this narrative review is to examine the incidence of persistent pain after CD; review briefly the underlying pathophysiology of persistent pain and the transition from acute to chronic pain (with particular emphasis on the uniqueness after CD); and to review modifiable risk factors and prevention strategies that identify at-risk patients and allow tailored treatment.

Oxytocin Effects on Pain Perception and Pain Anticipation

There is an ongoing debate whether the neuropeptide oxytocin (OT) modulates pain processing in humans. This study differentiates behavioral and neuronal OT effects on pain perception and pain anticipation by using a Pavlovian conditioning paradigm. Forty-six males received intranasally administered OT in a randomized, double-blind, placebo-controlled group design. Although OT exerted no direct effect on perceived pain, OT was found to modulate the blood oxygen level-dependent response in the ventral striatum for painful versus warm unconditioned stimuli and to decrease activity in the anterior insula (IS) with repeated thermal pain stimuli. Regarding pain anticipation, OT increased responses to CS_pain versus CS_minus in the nucleus accumbens. Furthermore, in the OT condition increased correct expectations, particularly for the most certain conditioned stimuli (CS)-unconditioned stimuli associations (CS_minus and CS_pain) were found, as well as greatest deactivations in the right posterior IS in response to the least certain condition (CS_warm) with posterior IS activity and correct expectancies being positively correlated. In conclusion, OT seems to have both a direct effect on pain processing via the ventral striatum and by inducing habituation in the anterior IS as well as on pain anticipation by boostering associative learning in general and the neuronal conditioned fear of pain response in particular. PERSPECTIVE: The neuropeptide OT has recently raised the hope to offer a novel avenue for modulating pain experience. This study found OT to modulate pain processing and to facilitate the anticipation of pain, inspiring further research on OT effects on the affective dimension of the pain experience.

Pain, Parental Involvement, and Oxytocin in the Neonatal Intensive Care Unit

Preterm infants (PTI) typically experience many painful and stressful procedures or events during their first weeks of life in a neonatal intensive care unit, and these can profoundly impact subsequent brain development and function. Several protective interventions during this sensitive period stimulate the oxytocin system, reduce pain and stress, and improve brain development. This review provides an overview of the environmental risk factors experienced by PTI during hospitalization, with a focus on the effects of pain, and early maternal separation. We also describe the long-term adverse effects of the simultaneous experiences of pain and maternal separation, and the potential beneficial effects of maternal vocalizations, parental contact, and several related processes, which appear to be mediated by the oxytocin system.