Effects of stress on pain threshold and tolerance in children with recurrent abdominal pain

Psychosocial Outcomes of Pain and Pain Management in Adults with Osteogenesis Imperfecta: A Qualitative Study

Osteogenesis imperfecta (OI) is a genetic disorder characterized by bone fragility and fractures, short stature, dental abnormalities, hearing loss, scoliosis, and chronic pain. Despite a growing literature on the functional outcomes of OI, limited research has explicitly examined the psychosocial outcomes of pain within OI. Adults with OI (N = 15) were interviewed to understand pain-related experiences through a thematic analysis of semi-structured interview data. Research team members, genetic research experts, and OI clinicians developed an interview guide focused on topics related to pain and mental health challenges. Participants' transcripts were coded by two independent coders; codes were then merged across coders and quotation outputs were subsequently abstracted (paraphrased then thematically classified) to identify common themes. Themes related to pain management variability regarding pain type, pain risk management and accessibility, pain outcomes (e.g., behavior, cognitive, affective), and pain exacerbating factors (e.g., individual, contextual) were identified. Participants reported chronic and acute pain, and despite the inaccessibility and stigmatization of pain medications (e.g., opioids), pharmacological treatments were the most common pain management approach. Participants reported negative pain outcomes, such as limited daily functioning and activity participation, fear, anger, anxiety, depression, and difficulty concentrating. Lastly, participants suggested that lack of physician and community knowledge on chronic pain in OI indirectly exacerbates both subjective pain intensity and outcomes. Although limited by a small, nondiverse sample, the current study provides valuable exploration of the unique pain experiences of adults with OI that may have implications for proactive management, treatment development, and clinician training.

Modulation of pain perception through transcranial alternating current stimulation and its nonlinear relationship with the simulated electric field magnitude

BACKGROUND

Oscillatory activities observed in multiple regions are closely associated with the experience of pain. Specifically, oscillatory activities within the theta- and beta-frequency bands, observed in the left dorsolateral prefrontal cortex (DLPFC), have been implicated in pain perception among healthy individuals and those with chronic pain. However, their physiological significance remains unclear.

METHODS

We explored the modulation of pain perception in healthy individuals by theta- and beta-band transcranial alternating current stimulation (tACS) over the left DLPFC and examined the relationship between the modulation effect and magnitude of the electric field elicited by tACS in the left DLPFC using computational simulation.

RESULTS

Our findings revealed that both theta- and beta-tACS increased the heat pain threshold during and after stimulation. Notably, the simulated electric field magnitude in the left DLPFC exhibited an inverted U-shaped relationship with the pain modulation effect for theta-tACS.

CONCLUSIONS

Our study findings suggested that there would be an optimal electric field strength to produce a high analgesic effect for theta-tACS.

SIGNIFICANCE

The application of theta- and beta-tACS interventions targeting the left DLPFC might facilitate the treatment of chronic pain. Furthermore, the attainment of effective pain modulation via theta-tACS over the DLPFC warrants the use of optimal stimulus intensity.

Neuropathic pain, mood, and stress-related disorders: A literature review of comorbidity and co-pathogenesis

Neuropathic pain can be caused by multiple factors, and its prevalence can reach 10% of the global population. It is becoming increasingly evident that limited or short-lasting response to treatments for neuropathic pain is associated with psychological factors, which include psychiatric comorbidities known to affect quality of life. It is estimated that 60% of patients with neuropathic pain also experience depression, anxiety, and stress symptoms. Altered mood, including stress, can be a consequence of several painful conditions but can also favor pain chronicization when preexisting. Despite the apparent tight connection between clinical pain and mood/stress disorders, the exact physiological mechanisms remain unclear. This review aims to provide an overview of state-of-the-art research on the mechanisms of pain related to the pathophysiology of depression, anxiety, and stress disorders.

Environmental factors and their impact on chronic pain development and maintenance

It is more than recognized and accepted that the environment affects the physiological responses of all living things, from bacteria to superior vertebrates, constituting an important factor in the evolution of all species. Environmental influences range from natural processes such as sunlight, seasons of the year, and rest to complex processes like stress and other mood disorders, infections, and air pollution, being all of them influenced by how each creature deals with them. In this chapter, it will be discussed how some of the environmental elements affect directly or indirectly neuropathic pain, a type of chronic pain caused by a lesion or disease of the somatosensory nervous system. For that, it was considered the edge of knowledge in translational research, thus including data from human and experimental animals as well as the applicability of such findings.

Investigating the Impact of Stress on Pain: A Scoping Review on Sense of Control, Social-Evaluative Threat, Unpredictability, and Novelty (STUN Model)

Background

Stress can have paradoxical effects on pain, namely hyperalgesia and hypoalgesia. Four situational characteristics activate the hypothalamic-pituitary-adrenal axis, leading to a physiological stress response: lacking Sense of control, social-evaluative Threat, Unpredictability and Novelty (STUN). This scoping review reports on the types of evidence published on the effects of STUN characteristics on pain outcomes.

Databases/Data Treatment

Searches of primary electronic databases were performed to identify articles published on adults between 1990 and 2021 that contained search terms on pain and stress/STUN characteristics. A total of 329 articles were included in the analysis.

Results

Only 3.3% of studies examined simultaneously >1 STUN component. Almost all observational studies (177/180) examined the association between perceived stress and pain without measuring physiological stress responses. Of the 130 experimental studies, 78 (60.0%) manipulated stressful characteristics through nociception, and only 38.5% assessed if/how stress manipulation impacted perceived stress.

Conclusion

There is a clear lack of integration of the characteristics that trigger a physiological stress response in the pain field. Only 3.3% of studies examined simultaneously more than one STUN component and there is an unequal attention given to individual components of the STUN framework. Recommendations for future research include selection of stress manipulations/measurements that are more precisely inducing/reflecting neurobiological mechanisms of stress responses to insure valid integration of scientific knowledge.

Stress-mediated dysregulation of the Rap1 small GTPase impairs hippocampal structure and function

The effects of repeated stress on cognitive impairment are thought to be mediated, at least in part, by reductions in the stability of dendritic spines in brain regions critical for proper learning and memory, including the hippocampus. Small GTPases are particularly potent regulators of dendritic spine formation, stability, and morphology in hippocampal neurons. Through the use of small GTPase protein profiling in mice, we identify increased levels of synaptic Rap1 in the hippocampal CA3 region in response to escalating, intermittent stress. We then demonstrate that increased Rap1 in the CA3 is sufficient in and of itself to produce stress-relevant dendritic spine and cognitive phenotypes. Further, using super-resolution imaging, we investigate how the pattern of Rap1 trafficking to synapses likely underlies its effects on the stability of select dendritic spine subtypes. These findings illuminate the involvement of aberrant Rap1 regulation in the hippocampus in contributing to the psychobiological effects of stress.

Expressed Beliefs about the Cause of Pain in a Pediatric Population: A Qualitative Study

(1) Background: The aims of this study are to explore what beliefs children and adolescents manifest about the cause of the pain they describe, to compare whether there are differences between beliefs by age and the persistence of pain, and to relate the explanations of the cause of pain with current scientific evidence. (2) Methods: a cross-sectional qualitative study was used. The primary endpoint of the study was obtaining explanations of the cause of pain recorded by means of an open-ended question. The participants were school-age children attending a charted school in the province of Barcelona. (3) Results: The children and adolescents proposed a diverse range of explanations for the cause of pain that they reported in their responses. The most frequent explanation for the cause of pain were pathologies and injuries (45.95%), ergonomic issues (22.60%) and psychological issues (15.95%). (4) Conclusions: There is a lot of variety in the explanations that young people give about the cause of their pain in schoolchildren aged between 10 and 16 years old. There exists a high prevalence of explanations non-associated with tissue damage (ENAD) concerning the causes of pain described. It is necessary that future health prevention programs dedicated to early ages consider which beliefs about the cause of pain are the most frequent in the pediatric population.

Job stress and chronic and widespread musculoskeletal pain: a cross-sectional analysis from the Brazilian Longitudinal Study of Adult Health Musculoskeletal

ABSTRACT

Musculoskeletal pain is a global health concern, and work-related psychosocial stress might be a potential contributing factor. This cross-sectional study investigates whether job stress is associated with chronic and widespread musculoskeletal pain in 2051 Brazilian active civil servants included in the Brazilian Longitudinal Study of Adult Health Musculoskeletal (ELSA-Brasil MSK). Job stress was assessed using the Effort-Reward Imbalance (ERI) questionnaire. Associations between ERI domains, categorized into tertiles, and chronic musculoskeletal pain (CMP) at any site and per number of affected sites (0, 1-2, ≥3-multisite pain) and body regions (0, 1-2, 3-generalized pain), were investigated using binary and multinomial logistic regression, adjusted for sociodemographic, occupational, and health covariates. The prevalence of CMP at any site, multisites, and generalized regions was 52.9%, 18.2%, and 9.5%, respectively. After adjustments, the lower the reward and the greater the overcommitment, the higher the odds of CMP at any site. The ERI domains were more strongly associated with multisite and generalized CMP than with CMP at any site. Multisite CMP was associated with lower reward and with greater effort, overcommitment, and effort-reward imbalance ratio. Chronic musculoskeletal pain according to body regions, especially generalized pain, was also associated with ERI domains effort (OR = 2.06; 95%CI = 1.33-3.21), overcommitment (OR = 3.44; 95%CI = 2.20-5.39), and effort-reward imbalance ratio (OR = 2.06; 95%CI = 1.30-3.27). Results reveal an association between job stress not only with CMP at any site but notably with the pain spread to other body sites or regions. Our findings suggest that lowering stress at work and discouraging overcommitment may help reduce the CMP burden, including reduction of CMP spread from one site or region of the body to another.

Separation from a bonded partner alters neural response to inflammatory pain in monogamous rodents

Pain experience is known to be modified by social factors, but the brain mechanisms remain unspecified. We recently established an animal model of social stress-induced hyperalgesia (SSIH) using a socially monogamous rodent, the prairie vole, in which males separated from their female partners (loss males) became anxious and displayed exacerbated inflammatory pain behaviors compared to males with partners (paired males). In the present study, to explore the neural pathways involved in SSIH, a difference in neuronal activation in pain-related brain regions, or "pain matrix", during inflammatory pain between paired and loss males was detected using Fos immunoreactivity (Fos-ir). Males were paired with a female and pair bonding was confirmed in all subjects using a partner preference test. During formalin-induced inflammatory pain, both paired and loss males showed a significant induction of Fos-ir throughout the analyzed pain matrix components compared to basal condition (without injection), and no group differences in immunoreactivity were found among the injected males in many brain regions. However, the loss males had significantly lower Fos-ir following inflammatory pain in the medial prefrontal cortex and nucleus accumbens shell than the paired males, even though base Fos-ir levels were comparable between groups. Notably, both regions with different Fos-ir are major components of the dopamine and oxytocin systems, which play critical roles in both pair bonding and pain regulation. The present results suggest the possibility that pain exacerbation by social stress emerges through alteration of signaling in social brain circuitry.

Dyadic analysis of adolescent friendships behaviours during pain: Comparison of those with chronic pain versus those without chronic pain

BACKGROUND

Social context has been found to influence pain intensity and tolerance. The aims of this study were to determine the impact of one type of social context on the painful experiences of adolescents with and without chronic pain by examining interactions within and across friendship dyads during experimental pain.

METHODS

Each adolescent in 61 same-sex friendship dyads (30 dyads with a chronic pain member) across three sites participated in the cold pressor task and acted as the observer during their friend's participation. They also completed a battery of measures to capture friendship features and pain outcomes. Pain intensity was measured using an 11-point numeric scale. Pain tolerance was measured by the length of time in the cold pressor device. Videotapes of their interactions were coded for verbal and non-verbal behaviours. A series of Actor Partner Independence Modelling, Hierarchical Multiple Regression and Multivariate Analysis of Covariance was used to analyse the data.

RESULTS

Friendship features were not associated with pain intensity or tolerance. Both members of dyads with a chronic pain member used fewer non-attending behaviours when they were observing their friend resulting in participants in those dyads having lower pain tolerance. Moreover, within dyads, one's friend's behaviours when experiencing pain influenced pain tolerance but only for those dyads with a chronic pain member.

CONCLUSIONS

Strategies aimed at improving social interactions for adolescents with chronic pain while they are experiencing pain are discussed. Research is needed to understand how different peer relationships influence pain tolerance in adolescents with chronic pain.

SIGNIFICANCE OF THE RESEARCH

During pain, patterns of interactions differ within and between adolescent friendship dyads when one has chronic pain (CP) versus controls. Dyads with a CP member use fewer non-attending behaviours despite non-attending behaviours rated as more helpful. Pain intensity was solely related to the participant's behaviour. Amongst dyads with a CP member, pain tolerance was also influenced by their friend's behaviours. Friends of adolescents with pain engage in more unhelpful behaviours perhaps decreasing the ability of CP adolescents to engage in social activities.

Systematic Review of Autonomic Nervous System Functioning in Pediatric Chronic Pain

OBJECTIVES

Chronic pain is a common and debilitating health problem that impacts up to one third of children and adolescents. The pathophysiological mechanisms of chronic pain are complex, but considerable research links dysfunction of the autonomic nervous system (ANS) and chronic pain in adults. No review of ANS functioning has been conducted in pediatric chronic pain. We systematically reviewed studies examining ANS activity among youth with primary chronic pain conditions.

METHODS

A systematic search of PsycINFO, PubMed, and CINAHL was conducted using specific search terms. Articles were included if studies measured heart rate, blood pressure, heart rate variability, galvanic skin responses, or pupillometry among children or adolescents with a chronic pain condition. Studies examining these factors in the context of a specific disease-related pain condition were excluded.

RESULTS

Of the 1304 articles screened, 15 studies met the criteria for inclusion in this review. All included studies were cross-sectional and primarily included youth with abdominal pain. Results revealed preliminary evidence of reduced parasympathetic activity among youth with pain as measured by heart rate variability. However, results were mixed across ANS indices. Measurement and procedural differences, in addition to a lack of control groups in some studies, limit the interpretability of the reviewed findings.

DISCUSSION

Additional studies with larger and more diverse samples of youth with various chronic primary pain conditions are needed to delineate possible relationships among ANS functioning and the development and maintenance of chronic pain in children and adolescents. Clinical implications and avenues for future research are discussed.

The interaction between stress and chronic pain through the lens of threat learning

Stress and pain are interleaved at multiple levels - interacting and influencing each other. Both are modulated by psychosocial factors including fears, beliefs, and goals, and are served by overlapping neural substrates. One major contributing factor in the development and maintenance of chronic pain is threat learning, with pain as an emotionally-salient threat - or stressor. Here, we argue that threat learning is a central mechanism and contributor, mediating the relationship between stress and chronic pain. We review the state of the art on (mal)adaptive learning in chronic pain, and on effects of stress and particularly cortisol on learning. We then provide a theoretical integration of how stress may affect chronic pain through its effect on threat learning. Prolonged stress, as may be experienced by patients with chronic pain, and its resulting changes in key brain networks modulating stress responses and threat learning, may further exacerbate these impairing effects on threat learning. We provide testable hypotheses and suggestions for how this integration may guide future research and clinical approaches in chronic pain.

Pain catastrophizing and pain acceptance are associated with pain severity and interference among methadone-maintained patients

OBJECTIVE

The present study examined whether pain catastrophizing and pain acceptance, two important targets of psychosocial interventions for chronic pain, are uniquely associated with pain severity and pain interference among patients on methadone maintenance treatment (MMT).

METHOD

A total of 133 MMT patients who reported experiencing some pain during the previous week completed a battery of self-report measures. Multiple regression was used to test whether pain catastrophizing and pain acceptance are related to pain severity and pain interference above and beyond covariates including demographics, emotional distress, and current methadone dose.

RESULTS

Both pain acceptance and catastrophizing were significantly associated with pain severity and pain interference while controlling for covariates.

CONCLUSIONS

Consistent with previous literature on patients with chronic pain but without opioid use disorder, our findings suggest that both pain catastrophizing and pain acceptance are potentially important intervention targets among MMT patients with co-occurring opioid use disorder and chronic pain.

Youth and Parent Appraisals of Participation in a Study of Spontaneous and Induced Pediatric Clinical Pain

The current study examined youths' and their parents' perceptions concerning participation in an investigation of spontaneous and induced pain during recovery from laparoscopic appendectomy. Youth (age range 5-17 years) and their parents independently completed surveys about their study participation. On a 0 (very negative) -to-10 (very positive) scale, both parents 9.4(1.3) [mean(SD)] and youth 7.9(2.4) rated their experience as positive. Among youth, experience ratings did not differ by pain severity and survey responses did not differ by age. Most youth (83%) reported they would tell another youth to participate. Ethical issues regarding instigation of pain in youth for research purposes are examined.

The Influence of Early Life Experience on Visceral Pain

Pain is the most reported and troublesome symptom of nearly all functional disorders affecting the genitourinary and gastrointestinal organs. Patients with irritable bowel syndrome (IBS), interstitial cystitis/painful bladder syndrome (IC/PBS), vulvodynia, and/or chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS; collectively termed chronic pelvic pain syndromes) report pain severe enough to impact quality of life and often suffer from symptoms of or are diagnosed with more than one of these syndromes. This increased comorbidity between chronic pelvic pain syndromes, and with pain disorders of disparate body regions, as well as with mood disorders, can be influenced by disruptions in the hypothalamic-pituitary-adrenal (HPA) axis, which regulates the response to stress and influences the perception of pain. Experiencing trauma, neglect, or abuse in early life can permanently affect the functioning of the HPA axis. As such, a significant proportion of patients suffering from comorbid chronic pelvic pain syndromes report a history of early life stress or trauma. Here we will report on how these early life experiences influence chronic pelvic pain in patients. We will also discuss various rodent models that have been developed to study this phenomenon to understand the mechanisms underlying HPA axis dysfunction, as well as potential underlying mechanisms connecting these syndromes to one another.

Partner Loss in Monogamous Rodents: Modulation of Pain and Emotional Behavior in Male Prairie Voles

OBJECTIVE

Pain is modulated by psychosocial factors, and social stress-induced hyperalgesia is a common clinical symptom in pain disorders. To provide a new animal model for studying social modulation of pain, we examined pain behaviors in monogamous prairie voles experiencing partner loss.

METHODS

After cohabitation with novel females, males (n = 79) were divided into two groups on the basis of preference test scores. Half of the males of each group were separated from their partner (loss group), whereas the other half remained paired (paired group). Thus, males from both groups experienced social isolation. Open field tests, plantar tests, and formalin tests were then conducted on males to assess anxiety and pain-related behaviors.

RESULTS

Loss males showing partner preferences (n = 20) displayed a significant increase in anxiety-related behavior in the open-field test (central area/total distance: 13.65% [1.58%] for paired versus 6.45% [0.87%] for loss; p < .001), a low threshold of thermal stimulus in the plantar test (withdrawal latencies: 9.69 [0.98] seconds for paired versus 6.15 [0.75] seconds for loss; p = .037), and exacerbated pain behaviors in the formalin test (total number of lifts: 40.33 [4.46] for paired versus 54.42 [1.91] for loss; p = .042) as compared with paired males (n = 20). Thermal thresholds in the plantar test significantly correlated with anxiety-related behavior in the open-field test (r = 0.64). No such differences were observed in the males that did not display partner preferences (r = 0.15).

CONCLUSIONS

Results indicate that social bonds and their disruption, but not social housing without bonding followed by isolation, modulate pain and emotion in male prairie voles. The prairie vole is a useful model for exploring the neural mechanisms by which social relationships contribute to pain and nociceptive processing in humans.

Past Pain Experience and Experimentally induced Pain Perception

Many intercurrent factors may be involved in the modulation of the pain message and its expression, such as the previous experience of pain built along the life. In this study, we aimed to determine whether susceptibility to experimentally induced pain is differentially influenced by the individual previous painful experience in subjects with schizophrenia (SC) major depression (MD), and controls (C).

METHODS

The SC (30), MD (32) and C (30) groups participated in experimental pain tests (application of pressure and induction of ischemia) after a semi-structured interview to make an inventory of the previous painful experiences, and the evaluation of anxiety either with autonomic (heart rate, blood pressure) or psychological (Hospital Anxiety Depression scale HAD) measures, and catastrophism.

RESULTS

The reported pain intensities, severities, duration, of the previous pain events, and the number of previous painful events were equivalent in the three groups, except for the number of painful events experimented before the last six months which was lower in the MD group. Experimental pain sensitivity was influenced by the diagnosis, the HAD scores or the number and intensities of previous lived painful events.

CONCLUSION

The lack of a past experience of pain was comparable for the different groups, suggesting that psychiatric disorders do not affect the experience of pain associated with daily life or past events. For each subject, the reported previous experience of pain influences the present feeling of pain.

Selective corticotropin-releasing factor 1 receptor antagonist E2508 reduces restraint stress-induced defecation and visceral pain in rat models

N-Cyclopropylmethyl-7-(2,6-dimethoxy-4-methoxymethylphenyl)-2-ethyl-N-(tetrahydro-2H-pyran-4-ylmethyl)pyrazolo[1,5-a]pyridin-3-amine tosylate (E2508) is a newly discovered selective corticotropin-releasing factor 1 receptor antagonist. Here, we investigated the effects of E2508 on wrap restraint stress-induced defecation and visceral pain in rats. Oral pretreatment with E2508 dose-dependently decreased stool weights after 20min wrap restraint stress and significant effects were observed at doses of 30 and 100mg/kg. However, E2508 did not affect basal defecation at doses up to 100mg/kg. In contrast, alosetron, a 5-HT₃ receptor antagonist, decreased both wrap restraint stress-induced and basal stool output at a dose of 0.1mg/kg. In a rat visceral pain model, subcutaneous injections of both E2508 (0.01 and 0.1mg/kg) and alosetron (0.001 and 0.01mg/kg) significantly decreased the number of abdominal muscle contractions induced by colonic distention, suggesting these drugs reduced visceral pain. Together, these results demonstrate E2508 has the potential to be an effective therapy for the treatment of irritable bowel syndrome with a lower risk of adverse events such as constipation compared with the current clinically used 5-HT₃ receptor antagonist.

Pain Catastrophizing Predicts Menstrual Pain Ratings in Adolescent Girls with Chronic Pain

OBJECTIVES

The current study aimed to explore relationships among self-reported menstrual pain ratings, acute laboratory pain, pain catastrophizing, and anxiety sensitivity in a sample of girls without pain (No Pain group) and girls with a chronic pain condition (Chronic Pain group).

SETTING

A laboratory at an off-campus Medical School office building.

SUBJECTS

Eighty-four postmenarchal girls (43 No Pain, 41 Chronic Pain) ages 10-17 participated in the study.

METHODS

All participants completed self-report questionnaires assessing menstrual pain, pain catastrophizing, and anxiety sensitivity and completed a cold pressor task. Pain intensity during the task was rated on a 0 (no pain) to 10 (worst pain possible) numeric rating scale.

RESULTS

After controlling for age, average menstrual pain ratings (without medication) were significantly correlated with cold pressor pain intensity for the No Pain group only. In the Chronic Pain group, menstrual pain ratings were significantly correlated with pain catastrophizing and anxiety sensitivity. In a multiple linear regression analysis, after controlling for age, only pain catastrophizing emerged as a significant predictor of menstrual pain ratings in the Chronic Pain group.

CONCLUSION

Results demonstrate differences in relationships among menstrual pain, acute laboratory pain, and psychological variables in girls with no pain compared with girls with chronic pain. In addition, pain catastrophizing may be a particularly salient factor associated with menstrual pain in girls with chronic pain that warrants further investigation.

Sustained Morphine Administration Induces TRPM8-Dependent Cold Hyperalgesia

It is not uncommon for patients chronically treated with opioids to exhibit opioid-induced hyperalgesia, and this has been widely reported clinically and experimentally. The molecular substrate for this hyperalgesia is multifaceted, and associated with a complex neural reorganization even in the periphery. For instance, we have recently shown that chronic morphine-induced heat hyperalgesia is associated with an increased expression of GluN2B containing N-methyl-D-aspartate receptors, as well as of the neuronal excitatory amino acid transporter 3/excitatory amino acid carrier 1, in small-diameter primary sensory neurons only. Cold allodynia is also a common complaint of patients chronically treated with opioids, yet its molecular mechanisms remain to be understood. Here we present evidence that the cold sensor TRPM8 channel is involved in opioid-induced hyperalgesia. After 7 days of morphine administration, we observed an upregulation of TRPM8 channels using patch clamp recording on sensory neurons and Western blot analysis on dorsal root ganglia. The selective TRPM8 antagonist RQ-00203078 blocked cold hyperalgesia in morphine-treated rats. Also, TRPM8 knockout mice failed to develop cold hyperalgesia after chronic administration of morphine. Our results show that chronic morphine upregulates TRPM8 channels, which is in contrast with the previous finding that acute morphine triggers TRPM8 internalization.

PERSPECTIVE

Patients receiving chronic opioid are sensitive to cold. We show in mice and rats that sustained morphine administration induces cold hyperalgesia and an upregulation of TRPM8. Knockout or selectively blocking TRPM8 reduces morphine-induced cold hyperalgesia suggesting TRPM8 is regulated by opioids.

Maternal Anxiety and Children's Laboratory Pain: The Mediating Role of Solicitousness

There has been limited empirical examination of how parent variables such as anxiety and solicitousness collectively impact child pain response. We sought to examine the relationships among maternal anxiety, solicitous parenting, and children’s laboratory anxiety and pain intensity in children with chronic pain. Participants included 80 children and adolescents (ages 8–18) with chronic pain and their mothers. Children completed questionnaires and lab pain tasks measuring their parents’ solicitous parenting, pressure, cold and heat pain anticipatory anxiety and pain intensity. Using bootstrapping analysis, maternal anxiety predicted child anticipatory anxiety and pain intensity in girls with chronic pain, which was mediated by the child’s report of parental solicitousness. For boys with chronic pain, maternal anxiety predicted boys’ anticipatory anxiety and pain intensity, with no support for mediation. This study adds to the growing literature demonstrating the impact of maternal anxiety on children’s pain. The study highlights the importance of considering parents in treatment designed to reduce children’s pain.

Psychosocial mechanisms for the transmission of somatic symptoms from parents to children

AIM

To examine familial aggregation of irritable bowel syndrome (IBS) via parental reinforcement/modeling of symptoms, coping, psychological distress, and exposure to stress.

METHODS

Mothers of children between the ages of 8 and 15 years with and without IBS were identified through the Group Health Cooperative of Puget Sound. Mothers completed questionnaires, including the Child Behavior Checklist (child psychological distress), the Family Inventory of Life Events (family exposure to stress), SCL-90R (mother psychological distress), and the Pain Response Inventory (beliefs about pain). Children were interviewed separately from their parents and completed the Pain Beliefs Questionnaire (beliefs about pain), Pain Response Inventory (coping) and Child Symptom Checklist [gastrointestinal (GI) symptoms]. In addition, health care utilization data was obtained from the automated database of Group Health Cooperative. Mothers with IBS (n = 207) and their 296 children were compared to 240 control mothers and their 335 children, while controlling for age and education.

RESULTS

Hypothesis 1: reinforcement of expression of GI problems is only related to GI symptoms, but not others (cold symptoms) in children. There was no significant correlation between parental reinforcement of symptoms and child expression of GI or other symptoms. Hypothesis 2: modeling of GI symptoms is related to GI but not non-GI symptom reporting in children. Children of parents with IBS reported more non-GI (8.97 vs 6.70, P < 0.01) as well as more GI (3.24 vs 2.27, P < 0.01) symptoms. Total health care visits made by the mother correlated with visits made by the child (rho = 0.35, P < 0.001 for cases, rho = 0.26, P < 0.001 for controls). Hypothesis 3: children learn to share the methods of coping with illness that their mothers exhibit. Methods used by children to cope with stomachaches differed from methods used by their mothers. Only 2/16 scales showed weak but significant correlations (stoicism rho = 0.13, P < 0.05; acceptance rho = 0.13, P < 0.05). Hypothesis 4: mothers and children share psychological traits such as anxiety, depression, and somatization. Child psychological distress correlated with mother's psychological distress (rho = 0.41, P < 0.001 for cases, rho= 0.38, P < 0.001 for controls). Hypothesis 5: stress that affects the whole family might explain the similarities between mothers and their children. Family exposure to stress was not a significant predictor of children's symptom reports. Hypothesis 6: the intergenerational transmission of GI illness behavior may be due to multiple mechanisms. Regression analysis identified multiple independent predictors of the child's GI complaints, which were similar to the predictors of the child's non-GI symptoms (mother's IBS status, child psychological symptoms, child catastrophizing, and child age).

CONCLUSION

Multiple factors influence the reporting of children's gastrointestinal and non-gastrointestinal symptoms. The clustering of illness within families is best understood using a model that incorporates all these factors.

Frequent abdominal pain in childhood and youth: a systematic review of psychophysiological characteristics

Background. Frequent abdominal pain (AP) in children and adolescents is often designated as functional gastrointestinal disorder. In contrast to research on psychological and social influences on the experience of AP in this population, psychophysiological features such as function of the autonomic nervous system, the central nervous system, or the endocrine system have rarely been studied. Methods. We conducted a systematic literature search for peer-reviewed journal articles referring to children with AP between 4 and 18 years. Studies on experimental baseline characteristics or reactivity of psychophysiological outcome parameters (autonomous nervous system, central nervous system, and endocrine parameters) were included. Key Results. Twelve of 18 included studies found psychophysiological differences between children with AP and healthy ones. These studies indicate a possible autonomic dysregulation and hypersensitivity of the central nervous system in children with AP following stimulation with stress or other intense stimuli. Mainly conflicting results were found regarding baseline comparisons of autonomic and endocrine parameters. Conclusions and Inferences. Frequent AP in children may be associated with an altered psychophysiological reaction on intense stimuli. It has to be considered that the current literature on psychophysiological characteristics of childhood AP is small and heterogeneous. In particular, multiparameter studies using validated experimental paradigms are lacking.

A practical guide and perspectives on the use of experimental pain modalities with children and adolescents

Use of experimental pain is vital for addressing research questions that would otherwise be impossible to examine in the real world. Experimental induction of pain in children is highly scrutinized given the potential for harm and lack of direct benefit to a vulnerable population. However, its use has critically advanced our understanding of the mechanisms, assessment and treatment of pain in both healthy and chronically ill children. This article introduces various experimental pain modalities, including the cold pressor task, the water load symptom provocation test, thermal pain, pressure pain and conditioned pain modulation, and discusses their application for use with children and adolescents. It addresses practical implementation and ethical issues, as well as the advantages and disadvantages offered by each task. The incredible potential for future research is discussed given the array of experimental pain modalities now available to pediatric researchers.

Neurobiology of stress-induced hyperalgesia

The intensity and severity of perceived pain does not correlate consistently with the degree of peripheral or central nervous system tissue damage or with the intensity of primary afferent or spinal nociceptive neurone activity. In this respect, the modulation of pain by emotion and context is now widely recognized. In particular, stress, fear and anxiety exert potent, but complex, modulatory influences on pain. Stress can either suppress pain (stress-induced analgesia) or exacerbate it (stress-induced hyperalgesia; SIH) depending on the nature, duration and intensity of the stressor. Herein, we review the methods and models used to study the phenomenon of SIH in rodents and humans and then present a detailed discussion of our current understanding of neural substrates and neurobiological mechanisms. The review provides perspectives and challenges for the current and future treatment of pain and the co-morbidity of pain with stress-related psychiatric disorders including anxiety and depression.

Computer-delivered social norm message increases pain tolerance

BACKGROUND

Few experimental studies have been conducted on social determinants of pain tolerance.

PURPOSE

This study tests a brief, computer-delivered social norm message for increasing pain tolerance.

METHODS

Healthy young adults (N = 260; 44 % Caucasian; 27 % Hispanic) were randomly assigned into a 2 (social norm) × 2 (challenge) cold pressor study, stratified by gender. They received standard instructions or standard instructions plus a message that contained artificially elevated information about typical performance of others.

RESULTS

Those receiving a social norm message displayed significantly higher pain tolerance, F(1, 255) = 26.95, p < .001, η p (2)  = .10 and pain threshold F(1, 244) = 9.81, p = .002, η p (2)  = .04, but comparable pain intensity, p > .05. There were no interactions between condition and gender on any outcome variables, p > .05.

CONCLUSIONS

Social norms can significantly increase pain tolerance, even with a brief verbal message delivered by a video.

Individual modulation of pain sensitivity under stress

OBJECTIVES

Stress has a strong influence on pain sensitivity. However, the direction of this influence is unclear. Recent studies reported both decreased and increased pain sensitivities under stress, and one hypothesis is that interindividual differences account for these differences. The aim of our study was to investigate the effect of stress on individual pain sensitivity in a relatively large female sample.

METHODS

Eighty female participants were included. Pain thresholds and temporal summation of pain were tested before and after stress, which was induced by the Mannheim Multicomponent Stress Test. In an independent sample of 20 women, correlation coefficients between 0.45 and 0.89 indicated relatively high test-retest reliability for pain measurements.

RESULTS

On average, there were significant differences between pain thresholds under non-stress and stress conditions, indicating an increased sensitivity to pain under stress. No significant differences between non-stress and stress conditions were found for temporal summation of pain. On an individual basis, both decreased and increased pain sensitivities under stress conditions based on Jacobson's criteria for reliable change were observed. Furthermore, we found significant negative associations between pain sensitivity under non-stress conditions and individual change of pain sensitivity under stress. Participants with relatively high pain sensitivity under non-stress conditions became less sensitive under stress and vice versa.

DISCUSSION

These findings support the view that pain sensitivity under stress shows large interindividual variability, and point to a possible dichotomy of altered pain sensitivity under stress.

Seasonal patterns of abdominal pain consultations among adults and children

BACKGROUND AND AIM

Consultations for chronic abdominal pain are frequent in adults and children. A seasonal pattern of abdominal pain consultations with winter predominance was shown in previous pediatric studies; however, no studies have investigated whether such a pattern exists in adult patients. Understanding the differences in seasonal patterns of abdominal pain consultations among adults and children may indicate that either different mechanisms exist for common chronic pain conditions or triggering factors may vary by age. The aim of the study was to investigate whether a seasonal variation in abdominal pain consultation patterns exists among adults and children.

METHODS

The number of outpatient consultations among children (5-17 years) and adults (18 years or older) with a diagnosis of abdominal pain of nonspecified origin (International Classification of Diseases-9 code 789.0) from May 2000 to December 2008 was identified in an administrative claims database. The primary outcome measure was the rate of abdominal pain consultations (total number of abdominal pain consultations/total number of distinct patients by month×1000) by season in children and adults. Seasons were defined as follows: winter (December-February), spring (March-May), summer (June-August), and fall (September-November). A trend test was conducted to determine the degree of linearity in the patterns between the 2 groups. Among children, subanalyses by age 5 to 11 years and 12 to 17 years and sex were conducted.

RESULTS

A total of 172.4 million distinct patients (13.4% children, 87.6% adults) were identified in the database between May 2000 and December 2008. During the same time period, 15.6 million patient consultations for abdominal pain were identified (10.1% children, 89.9% adults). Children demonstrated a seasonal pattern in abdominal pain consultations, which best fit a quadratic regression curve, with consultations less common during the summer months. Abdominal pain consultations in adults were linear with no seasonal predominance. The trend in seasonal variation of abdominal pain consultations among children stratified by age and sex remained consistent with the overall child population.

CONCLUSIONS

Abdominal pain consultations in children are less common during summer months, whereas no evidence of seasonal pattern of consultation was found in adults. Factors involved in the pathogenesis of abdominal pain in adults and children may differ.

Bispectral index dynamics during propofol hypnosis is similar in red-haired and dark-haired subjects

BACKGROUND

We have previously shown that red hair is associated with increased desflurane requirement for immobility, compared with dark hair. The effect of red hair on IV anesthetic requirement remains unknown. We tested the hypothesis that the propofol concentration in the effect site associated with half maximal electroencephalogram response, Ce50, is at least 50% higher in subjects with red hair.

METHODS

We modeled the propofol concentration versus electroencephalogram response relationship using a 2-step approach in 29 healthy dark- and red-haired volunteers receiving a propofol infusion to produce loss of consciousness. Bispectral Index (BIS) was the measure of drug effect. The parameters of a 3-compartment pharmacokinetic model were fit to measured arterial propofol concentrations. The relationship between effect-site propofol concentration (Ce) and BIS was characterized using a sigmoid Emax model. Model performance and accuracy of the estimated parameters were evaluated using accepted metrics and bootstrap resampling. The effect of hair color on the Ce50 for BIS response in the final model was assessed using a threshold of 6.63 (P<0.01) in reduction of -2 log likelihood. The influence of body weight on the model was also assessed.

RESULTS

The inclusion of hair color as a model covariate did not improve either the pharmacokinetic or the pharmacodynamic model. A separate analysis for the dark- and red-haired subjects estimated a median (95% confidence interval) Ce50 BIS of 2.71 μg/mL (2.28-3.36 μg/mL) and 2.57 μg/mL (1.68-3.60 μg/mL), respectively. Body weight was a significant covariate for the CL1 and V1.

CONCLUSIONS

Red hair phenotype does not affect the pharmacokinetics or pharmacodynamics of propofol.

Relationship of neuroticism and laboratory pain in healthy children: does anxiety sensitivity play a role?

Both neuroticism, a higher-order, stable personality trait, and anxiety sensitivity (AS), a lower-order pain-related construct, have been associated with pain, although no research exists examining the relationship of both these constructs to acute pain in children. In the current study, 99 healthy children (53 girls) completed self-report measures of neuroticism and AS before undergoing pain tasks involving cold and pressure pain. We hypothesized that both neuroticism and AS would be correlated with acute pain responses, but that AS would at least partially mediate the relationship between neuroticism and pain responses. Results indicated significant correlations between neuroticism, AS, and anticipatory anxiety, pain intensity and pain bother. Mediational models revealed that AS partially mediated relationships between neuroticism and pain intensity/bother, and fully mediated relationships between neuroticism and anticipatory anxiety. These data suggest that, at least in children, neuroticism may be best understood as a vulnerability factor for elevated pain responses, especially when coupled with a fear of bodily sensations.

The effect of a mental stressor on conditioned pain modulation in healthy subjects

Background and purpose

In animal studies, enhanced sensitivity to painful stimuli succeeding chronic stress has been reported, while acute stress is reported to induce analgesia. Human studies on the effect of mental stress on pain are more equivocal. A disturbed stress-response resulting in an increased sensitivity to painful stimuli has also been discussed as a potential mechanism for e.g., the fibromyalgia syndrome. Endogenous analgesia may be studied in humans by measuring the analgesic effect of heterotopic noxious conditioning stimulation. In neurophysiological animal studies this phenomenon was originally denoted “diffuse noxious inhibitory controls” (DNIC), but for human studies it has been suggested to use the term conditioned pain modulation (CPM).

The clinical relevance of aberrances in CPM is not clear. Inhibitory CPM is reported as being reduced in several medically unexplained syndromes with musculoskeletal pain aggravated by mental stress. However, whether the reported reduced CPM effects are causally related to clinical pain is unknown.

In the present study the effect of a mental stressor on CPM is studied.

Methods

With tourniquet-induced pain as the conditioning stimulus we estimated the CPM effect in twenty healthy subjects. Heat pain threshold (HPT), supra-threshold heat pain level (SHPL) and pressure pain threshold (PPT) were used as test stimuli. Measurements were performed at baseline, after a stressful task and after a non-stressful task presented in a blinded cross-over design. We used repeated-measures ANOVAs in the analysis with simple contrasts for post hoc analysis.

Results

With a ANOVA repeated measures model we found a significant task effect (F = 18.5, p ≤ 0.001), indicating that CPM was successfully induced. In our ANOVA model, we found a significant effect of stress in the contrast analysis (F = 5.2, p = 0.037), indicating that CPM was affected by the stressful task. The effects on PPT could not be analyzed due to a significant carry-over effect (for PPT only).

Conclusions

In the present blinded crossover study, we found a significant small to medium inhibitory effect of mental stress upon the CPM of thermal pain.

Implications

Our results suggest that previously reported reduced inhibitory CPM in several medically unexplained syndromes with musculoskeletal pain aggravated by mental stress possibly can be related to confounding or clinically relevant stress level differences. However, the result might be modality-specific. Further studies in patients are obviously needed, and the impact of mental stress on CPM should be investigated also with other stressors.

Experimental pain hypersensitivity in schizophrenic patients

OBJECTIVE

Whether schizophrenic patients are hypoalgesic or feel pain in the same manner as unaffected individuals can affect the primary care of schizophrenic patients, which often involves an assessment of pain severity made by a medical provider. This study was developed to explore the pain sensitivity of schizophrenics under conditions similar to those of a medical examination that included investigating for sites of pain.

METHODS

We developed 2 experimental models of pain induction using either pressure or ischemia and used them with 35 schizophrenic patients and 35 controls to record: (1) the stimulus intensity required to induce moderate pain; and (2) the pain intensity induced by a predetermined level of pressure. Clinical data were also collected for the schizophrenic group.

RESULTS

Schizophrenic patients needed less pressure (P=0.006) and a shorter duration of ischemia (P<0.001) than controls to record moderate pain, and they felt more pain from a fixed pressure stimulus (P<0.001). Pain histories for the previous 6 months and the heart rate variations that occurred during the tests did not differ between the groups. Pain responses were unrelated to the clinical characteristics of the schizophrenic patients, although hallucination production correlated with the pain felt during the fixed pressure test.

DISCUSSION

Under these conditions, schizophrenic patients were hypersensitive to pain induction compared with normal individuals. The hypoalgesia typically associated with schizophrenic patients may correspond to fewer than normal reports of pain, rather than to impaired sensations of pain. This should be taken into account during routine medical practice.

Stress and visceral pain: from animal models to clinical therapies

Epidemiological studies have implicated stress (psychosocial and physical) as a trigger of first onset or exacerbation of irritable bowel syndrome (IBS) symptoms of which visceral pain is an integrant landmark. A number of experimental acute or chronic exteroceptive or interoceptive stressors induce visceral hyperalgesia in rodents although recent evidence also points to stress-related visceral analgesia as established in the somatic pain field. Underlying mechanisms of stress-related visceral hypersensitivity may involve a combination of sensitization of primary afferents, central sensitization in response to input from the viscera and dysregulation of descending pathways that modulate spinal nociceptive transmission or analgesic response. Biochemical coding of stress involves the recruitment of corticotropin releasing factor (CRF) signaling pathways. Experimental studies established that activation of brain and peripheral CRF receptor subtype 1 plays a primary role in the development of stress-related delayed visceral hyperalgesia while subtype 2 activation induces analgesic response. In line with stress pathways playing a role in IBS, non-pharmacologic and pharmacologic treatment modalities aimed at reducing stress perception using a broad range of evidence-based mind-body interventions and centrally-targeted medications to reduce anxiety impact on brain patterns activated by visceral stimuli and dampen visceral pain.

A meta-analysis of the use of nonsteroidal antiinflammatory drugs for pediatric postoperative pain

BACKGROUND

Opioid side effects are a great concern during the postoperative period in children. Nonsteroidal antiinflammatory drugs (NSAIDs) have been shown to effectively decrease postoperative pain, but their opioid-sparing effect is still controversial. In this present meta-analysis, we investigated the postoperative opioid-sparing effect of NSAIDs in children.

METHODS

A comprehensive literature search was conducted to identify clinical trials using NSAIDs and opioids as perioperative analgesic compounds in children and infants. Outcomes measured were opioid consumption, pain intensity, postoperative nausea and vomiting (PONV), and urinary retention. All outcomes were studied during postanesthesia care unit (PACU) stay and the first 24 postoperative hours. Data from each trial were combined to calculate the pooled odds ratios (ORs) or standardized mean difference (SMD) and their 95% confidence interval.

RESULTS

Twenty-seven randomized controlled studies were analyzed. Perioperative administration of NSAIDs decreased postoperative opioid requirement (both in the PACU and during the first 24 postoperative hours; SMD = -0.66 [-0.84, -0.48] and -0.83 [-1.11, -0.55], respectively), pain intensity in the PACU (SMD = -0.85 [-1.24, -0.47]), and PONV during the first 24 postoperative hours (OR = 0.75 [0.57-0.99]). NSAIDs did not decrease pain intensity during the first 24 postoperative hours (OR = 0.56 [0.26-1.2]) and PONV during PACU stay (OR = 1.02 [0.73-1.44]). Subgroup analysis according to the timing of NSAID administration (intraoperative versus postoperative), type of surgery, or coadministration of paracetamol did not show any influence of these factors on the studied outcomes except the reduction of pain intensity and the incidence of PONV during the first 24 postoperative hours, which were influenced by the coadministration of paracetamol and the type of surgery, respectively.

CONCLUSION

This meta-analysis shows that perioperative NSAID administration reduces opioid consumption and PONV during the postoperative period in children.

Stress-related alterations of visceral sensation: animal models for irritable bowel syndrome study

Stressors of different psychological, physical or immune origin play a critical role in the pathophysiology of irritable bowel syndrome participating in symptoms onset, clinical presentation as well as treatment outcome. Experimental stress models applying a variety of acute and chronic exteroceptive or interoceptive stressors have been developed to target different periods throughout the lifespan of animals to assess the vulnerability, the trigger and perpetuating factors determining stress influence on visceral sensitivity and interactions within the brain-gut axis. Recent evidence points towards adequate construct and face validity of experimental models developed with respect to animals' age, sex, strain differences and specific methodological aspects such as non-invasive monitoring of visceromotor response to colorectal distension as being essential in successful identification and evaluation of novel therapeutic targets aimed at reducing stress-related alterations in visceral sensitivity. Underlying mechanisms of stress-induced modulation of visceral pain involve a combination of peripheral, spinal and supraspinal sensitization based on the nature of the stressors and dysregulation of descending pathways that modulate nociceptive transmission or stress-related analgesic response.

Stress and visceral pain: from animal models to clinical therapies

Epidemiological studies have implicated stress (psychosocial and physical) as a trigger of first onset or exacerbation of irritable bowel syndrome (IBS) symptoms of which visceral pain is an integrant landmark. A number of experimental acute or chronic exteroceptive or interoceptive stressors induce visceral hyperalgesia in rodents although recent evidence also points to stress-related visceral analgesia as established in the somatic pain field. Underlying mechanisms of stress-related visceral hypersensitivity may involve a combination of sensitization of primary afferents, central sensitization in response to input from the viscera and dysregulation of descending pathways that modulate spinal nociceptive transmission or analgesic response. Biochemical coding of stress involves the recruitment of corticotropin releasing factor (CRF) signaling pathways. Experimental studies established that activation of brain and peripheral CRF receptor subtype 1 plays a primary role in the development of stress-related delayed visceral hyperalgesia while subtype 2 activation induces analgesic response. In line with stress pathways playing a role in IBS, non-pharmacologic and pharmacologic treatment modalities aimed at reducing stress perception using a broad range of evidence-based mind-body interventions and centrally-targeted medications to reduce anxiety impact on brain patterns activated by visceral stimuli and dampen visceral pain.

Violence at the workplace increases the risk of musculoskeletal pain among nursing home workers

BACKGROUND

Despite the high prevalences of workplace physical violence and musculoskeletal symptoms among health care workers, very few studies have examined the relationship between these two phenomena.

METHODS

We surveyed 920 clinical nursing home workers by questionnaire regarding musculoskeletal pain in the low back, shoulders, wrists or hands, and knees. Information was also collected on exposure to physical assaults at work during the preceding 3 months, other workplace safety features, physical workload and psychosocial work environment. Log-binomial regression was used to estimate the prevalence ratios (PR) with 95% CIs.

RESULTS

Almost one-half of respondents reported being assaulted at least once during the preceding 3 months by a resident or resident's visitor. The prevalence of low back pain increased from 40% among non-assaulted workers to 70% among those assaulted three or more times. The highest risk was found for widespread pain (three or more areas), with an adjusted PR of 2.7 (95% CI 1.8 to 3.9) for workers assaulted three or more times. Good workplace safety buffered the effects, so that violence increased the risk of most pains considerably less in a work environment perceived to be safe.

CONCLUSIONS

To our knowledge, this is the first study to show a dose-response association between physical assaults and musculoskeletal pain in a health care setting where violence is a frequent occurrence. This emphasises the need to address violence as a workplace hazard through practical measures for prevention as well as in future aetiological research on musculoskeletal disorders.

The role of corticosteroids and stress in chronic pain conditions

The relationship between corticosteroids (endogenous and exogenous) and stress is well known, as is the use of steroids as concomitant treatment in pain management during acute inflammation. In the past, steroids have not been considered the first line of treatment in pain management. In this review, we examine new scientific and clinical evidence that demonstrates the direct role that steroids play in the generation and clinical management of chronic pain. We will discuss the new findings demonstrating the fact that steroids and related mediators produce paradoxical effects on pain such as analgesia, hyperalgesia, and even placebo analgesia. In addition, we will examine the physiologic effect of stress, high allostatic load, and idiopathic disease states such as chronic fatigue syndrome, fibromyalgia, irritable bowel syndrome, and burnout. The recently observed positive relationship between glutaminergic activity in the insula and clinical pain will be examined in the context of understanding the central role of steroids in chronic pain. The complex role of the hypothalamic-pituitary-adrenal axis in pain will be discussed as well as other heterogeneous forms of chronic pain that involve many components of the central nervous system. Components of the hypothalamic-pituitary-adrenal axis have paradoxical effects on certain types of pain that are dependent on dose and on site (whether peripheral or central) and mode of application. Recent studies on glia have shown that they prolong a state of neuronal hypersensitization in the dorsal root ganglia by releasing growth factors and other substances that act on the immune system. We will discuss the implication of these new findings directly linking pain to steroids, stress, and key higher brain regions in the context of future therapeutic targets.

Self-reported and laboratory-based responses to stress in children with recurrent pain and anxiety

OBJECTIVE

To examine heart rate (HR) responses to and coping with stress in children with recurrent abdominal pain (RAP), anxiety, and healthy controls.

METHODS

A clinical sample (children with RAP and children with anxiety) was compared to control children on self-reported and HR responses to stress and a laboratory test of pain tolerance and intensity (cold pressor).

RESULTS

Children in the clinical sample had elevated HRs compared to healthy controls before, during, and after laboratory tasks. Self-reported stress reactivity to social stress was positively correlated with HR at all study time intervals. Secondary control coping with social stress was negatively correlated with HR at most study time intervals. Internalizing symptoms were positively correlated with HR and self-reported stress reactivity.

CONCLUSIONS

Stress reactivity, as reflected in both self-reported and HR responses to laboratory stressors, is related to the presence of both RAP and anxiety in children.

Hypoalgesia related to elevated resting blood pressure is absent in adolescents and young adults with a history of functional abdominal pain

Elevated resting blood pressure (BP) is hypoalgesic in healthy individuals, but this effect is absent in adults with chronic somatic pain. This study tested whether BP-related hypoalgesia is similarly altered in individuals with a history of chronic visceral pain in childhood. Resting BP was assessed in 94 adolescents and young adults with a known history of childhood functional abdominal pain (FAP) and 55 comparable healthy controls. Responses to an acute heat pain stimulus were then evaluated following exposure to two laboratory stressors. A significant participant type x systolic BP (SBP) interaction (p<.005) revealed that elevated resting SBP was associated with significantly higher heat pain threshold (p<.001) in healthy controls, but was unrelated to pain threshold in the FAP group. A similar pattern was observed for heat pain tolerance, with elevated SBP linked to significantly higher pain tolerance (p<.05) in healthy controls, but unrelated to tolerance in the FAP group. Dysfunction in BP-related hypoalgesia associated with FAP was evident regardless of whether childhood FAP had resolved or still persisted at the time of laboratory testing. Subgroup analyses indicated that BP-related hypoalgesia (in healthy controls) and FAP-linked absence of this hypoalgesia was observed only among females. Result suggest that childhood visceral chronic pain may be associated with relatively long-lasting dysfunction in overlapping systems modulating pain and BP that persists even after FAP resolves. Potential implications for later hypertension risk are discussed.

Acupuncture analgesia for temporal summation of experimental pain: a randomised controlled study

BACKGROUND

Temporal summation of pain, a phenomenon of the central nervous system (CNS), represents enhanced painful sensation or reduced pain threshold upon repeated stimulation. This pain model has been used to evaluate the analgesic effect of various medications on the CNS.

AIMS

The present study aimed to evaluate the effects and characteristics of analgesia induced by electroacupuncture (EA), manual acupuncture (MA) and non-invasive sham-acupuncture (SA) in healthy humans on temporal summation of pain.

METHODS

Thirsty-six pain-free volunteers were randomised into one of the three groups EA (2/100 Hz), MA or SA. Acupuncture intervention was on ST36 and ST40 on the dominant leg delivered by an acupuncturist blinded to the outcome assessment. Both subjects and the evaluator were blinded to the treatment allocation. Pain thresholds to a single pulse (single pain threshold, SPT) and repeated pulses electrical stimulation (temporal summation thresholds, TST) were measured before, 30 min after and 24h after each treatment.

RESULTS

The baseline values of three groups were comparable. Compared to SA, EA significantly increased both SPT and TST immediately after the treatment on the treatment leg as well as 24h after on both the treatment and non-treatment legs (ANOVA, p<0.05). MA also increased SPT and TST, but the changes were not significantly different from those induced by SA.

CONCLUSION

EA induces bilateral, segmentally distributed and prolong analgesia on both SPT and TST, indicating a non-centrally specific effect. This effect needs to be verified with heat or mechanical model and in pain patients.