The long-term impact of early life pain on adult responses to anxiety and stress: Historical perspectives and empirical evidence

The relationship between neonatal stress in preterm infants and developmental outcomes at the corrected age of 24-30 months

Aim

The aim of research was to study the relationship between the stress experienced by preterm infants in the neonatal intensive care unit (NICU) and developmental status in the follow up, and to establish factors, associated with their neurodevelopment.

Methods

The first stage of research involved measuring stress markers (cortisol, melatonin) in infants (n = 56) during their NICU stay; the second phase assessed the developmental status at the corrected age of 24-30 months.

Results

The total ASQ-3 score, communication, problem solving, and personal-social skills scores at the corrected age of 24-30 months were positively correlated with melatonin level determined in the neonatal period (r = 0.31, p = 0.026; r = 0.36, p = 0.009; r = 0.30, p = 0.033, and r = 0.32; p = 0.022 respectively). In the same time, ASQ-3 communication and personal-social scores were negatively correlated with cortisol level (r = -0.31, p = 0.043; r = -0.35, p = 0.022). The ROC-curve analysis revealed that a decrease of melatonin below 3.44 ng/mL and 3.71 ng/mL during the neonatal period could predict communication and problem-solving delay, respectively. An increase in cortisol above 0.64 mcg/dl is predictive in personal-social delay. Negative correlation was identified between the NICU and total hospital stay duration and ASQ-3 communication scores in the follow-up (r = -0.27; p = 0.049 and r = -0.41; p = 0.002, respectively). The duration of mechanical ventilation was negatively correlated with gross motor scores (r = -0.46; p = 0.043). Apgar score was positively correlated with ASQ-3 communication (r = 0.29; p = 0.032) and personal-social scores (r = 0.28; p = 0.034); maternal age-with ASQ-3 total (r = 0.29; p = 0.034), communication (r = 0.37; p = 0.006), and personal-social scores (r = 0.29; p = 0.041). Positive correlations were observed between gestational age and communication scores (r = 0.28; p = 0.033). Infants who suffered neonatal sepsis had significantly often delay of communication (p = 0.014) and gross motor skills (p = 0.016). Children who required mechanical ventilation were more likely to have communication delay (p = 0.034).

Conclusion

Developmental outcomes in preterm infants at the corrected age of 24-30 months were associated with neonatal stress. Correlations between the communication, problem-solving and personal-social development in the follow up and cortisol and melatonin levels determined in the neonatal period supported this evidence. Factors as low gestational age, duration of hospital and NICU stay, mechanical ventilation, and sepsis were associated with more frequent delays in communication, gross motor and problems-solving skills.

Long-term effects of neonatal pain and sucrose treatment

Purpose

In neonatal intensive care units, applying sucrose solution for analgesia is now a routine treatment for mild procedural pain. Studies of animal and human infants provide clear evidence of benefits in the short term, but few studies have investigated the long term benefits. Thus, we determined whether sucrose could ameliorate painful stimulation during infancy in Sprague-Dawley rats and also explored the long-term effects of repeated sucrose administration during infancy. Female and male rats were included to investigate sex-related differences.

Methods

Rat pups were stimulated either with painful or tactile stimuli for the first 14 days of their lives. Pups were pretreated either with sucrose or not treated before stimulation. Behavioral tests were conducted during adolescence and adulthood. Hotplate, rotarod, open field, elevated plus maze, and radial arm water maze tests were employed to assess the behavioral consequences of early life manipulations and treatments.

Results

Painful stimulation during infancy increased the sensitivity to pain later in life, and sucrose did not remedy this effect. Motility, coordination, anxiety, and cognition tests in adulthood obtained mixed results. Pain during infancy appeared to increase anxiety during adulthood. Learning and memory in adulthood were affected by pain during infancy, and sucrose had a negative effect even in the absence of pain. No sex-related differences were observed in any of the behavioral tests by employing this model of neonatal pain.

Conclusion

Painful stimulation during infancy resulted in deficiencies in some behavioral tests later in life. Sucrose pretreatment did not mitigate these shortcomings and it actually resulted in negative outcomes.

Infant pain vs. pain with parental suppression: Immediate and enduring impact on brain, pain and affect

BACKGROUND

In the short term, parental presence while a human infant is in pain buffers the immediate pain responses, although emerging evidence suggests repeated social buffering of pain may have untoward long-term effects.

METHODS/FINDING

To explore the short- and long-term impacts of social buffering of pain, we first measured the infant rat pup's [postnatal day (PN) 8, or 12] response to mild tail shock with the mother present compared to shock alone or no shock. Shock with the mother reduced pain-related behavioral activation and USVs of pups at both ages and reduced Fos expression in the periaqueductal gray, hypothalamic paraventricular nucleus, and the amygdala at PN12 only. At PN12, shock with the mother compared to shock alone differentially regulated expression of several hundred genes related to G-protein-coupled receptors (GPCRs) and neural development, whereas PN8 pups showed a less robust and less coherent expression pattern. In a second set of experiments, pups were exposed to daily repeated Shock-mother pairings (or controls) at PN5-9 or PN10-14 (during and after pain sensitive period, respectively) and long-term outcome assessed in adults. Shock+mother pairing at PN5-9 reduced adult carrageenan-induced thermal hyperalgesia and reduced Fos expression, but PN10-14 pairings had minimal impact. The effect of infant treatment on adult affective behavior showed a complex treatment by age dependent effect. Adult social behavior was decreased following Shock+mother pairings at both PN5-9 and PN10-14, whereas shock alone had no effect. Adult fear responses to a predator odor were decreased only by PN10-14 treatment and the infant Shock alone and Shock+mother did not differ.

CONCLUSIONS/SIGNIFICANCE

Overall, integrating these results into our understanding of long-term programming by repeated infant pain experiences, the data suggest that pain experienced within a social context impacts infant neurobehavioral responses and initiates an altered developmental trajectory of pain and affect processing that diverges from experiencing pain alone.

Evidence-based severity assessment of the forced swim test in the rat

The forced swim test (FST) is a traditional assay, which has been used for more than 40 years to assess antidepressant effects of novel drug candidates. In recent years, a debate about the test has focused on the assumption that the FST is highly aversive and burdening for the animals because of the earlier anthropomorphic interpretation and designation as a "behavioral despair test". The Directive 2010/63/EU and the German Animal Welfare law require a prospective severity classification of the planned experimental procedures. Still, an objective examination of the animals' burden in this test has not been performed yet. To fill this gap, we conducted an evidence-based severity assessment of the forced swim test in rats according to a 'standard protocol' with a water temperature of 25°C. We examined parameters representing the physiological and the affective state, and natural as well as locomotion-associated behaviors in three separate experiments to reflect as many dimensions as possible of the animal's condition in the test. Hypothermia was the only effect observed in all animals exposed to the FST when using this standard protocol. Additional adverse effects on body weight, food consumption, and fecal corticosterone metabolite concentrations occurred in response to administration of the antidepressant imipramine, which is frequently used as positive control when testing for antidepressant effects of new substances. We conclude that this version of the FST itself is less severe for the animals than assumed, and we suggest a severity classification of 'moderate' because of the acute and short-lasting effects of hypothermia. To refine the FST according to the 3Rs, we encourage confirming the predictive validity in warmer water temperatures to allow the rats to maintain physiological body temperature.

Trauma-Informed Care in the Neonatal Intensive Care Unit: Through the Lens of the COVID-19 Pandemic

Trauma is rooted in an individual's experience of an event that leads to physical or mental harm and can have a long-lasting, unfavorable effect on their well-being and functioning. Being aware of the effects of trauma, recognizing its signs, understanding how it informs individual responses, and actively trying to prevent re-traumatization are the tenets of trauma-informed care. Admission to the neonatal intensive care unit (NICU) is widely considered to be an extremely stressful time for parents and infants alike. With the emergence of the coronavirus disease 2019 (COVID-19) pandemic, there were significant changes in healthcare delivery. Widespread closures, restrictions due to infection control measures, the spread of misinformation, increased psychosocial hardships, and amplification of cultural, gender, and racial biases intensified NICU-related stressors. Adoption of the principles of trauma-informed care, as defined by the Substance Abuse Mental Health Services Administration, to the NICU can help buffer some of these stressors. We present a review of these principles viewed through the lens of the COVID-19 pandemic. The lessons learned will help inform practices and policies and allow us to navigate similar challenges more effectively in the future.

Assessment of neonatal pain: uni- and multidimensional evaluation scales

Neonatal pain is a problem that is easily overlooked. According to the status quo of neonatal pain management, commonly 9 scales are used for evaluation of neonatal pain; details of the specific indicators, such as the applicable neonatal gestational age range, score, and the type of pain, for the domestic references are provided so as to provide reference for the proper evaluation and standardized management of neonatal pain, as well as to promote the management level of neonatal pain.

Associations of Mitochondrial Function, Stress, and Neurodevelopmental Outcomes in Early Life: A Systematic Review

Early life stress is commonly experienced by infants, especially preterm infants, and may impact their neurodevelopmental outcomes in their early and later lives. Mitochondrial function/dysfunction may play an important role underlying the linkage of prenatal and postnatal stress and neurodevelopmental outcomes in infants. This review aimed to provide insights on the relationship between early life stress and neurodevelopment and the mechanisms of mitochondrial function/dysfunction that contribute to the neuropathology of stress. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement was used to develop this systematic review. PubMed, Scopus, PsycINFO, and Biosis databases were searched for primary research articles published between 2010 and 2021 that examined the relationships among mitochondrial function/dysfunction, infant stress, and neurodevelopment. Thirty studies were identified. There is evidence to support that mitochondrial function/dysfunction mediates the relationship between prenatal and postnatal stress and neurodevelopmental outcomes in infants. Maternal transgenerational transmission of mitochondrial bioenergetic patterns influenced prenatal stress induced neurodevelopmental outcomes and behavioral changes in infants. Multiple functionally relevant mitochondrial proteins, genes, and polymorphisms were associated with stress exposure. This is the first review of the role that mitochondrial function/dysfunction plays in the association between stress and neurodevelopmental outcomes in full-term and preterm infants. Although multiple limitations were found based on the lack of data on the influence of biological sex, and due to invasive sampling, and lack of longitudinal data, many genes and proteins associated with mitochondrial function/dysfunction were found to influence neurodevelopmental outcomes in the early life of infants.

Signature for Pain Recovery IN Teens (SPRINT): protocol for a multisite prospective signature study in chronic musculoskeletal pain

INTRODUCTION

Current treatments for chronic musculoskeletal (MSK) pain are suboptimal. Discovery of robust prognostic markers separating patients who recover from patients with persistent pain and disability is critical for developing patient-specific treatment strategies and conceiving novel approaches that benefit all patients. Given that chronic pain is a biopsychosocial process, this study aims to discover and validate a robust prognostic signature that measures across multiple dimensions in the same adolescent patient cohort with a computational analysis pipeline. This will facilitate risk stratification in adolescent patients with chronic MSK pain and more resourceful allocation of patients to costly and potentially burdensome multidisciplinary pain treatment approaches.

METHODS AND ANALYSIS

Here we describe a multi-institutional effort to collect, curate and analyse a high dimensional data set including epidemiological, psychometric, quantitative sensory, brain imaging and biological information collected over the course of 12 months. The aim of this effort is to derive a multivariate model with strong prognostic power regarding the clinical course of adolescent MSK pain and function.

ETHICS AND DISSEMINATION

The study complies with the National Institutes of Health policy on the use of a single internal review board (sIRB) for multisite research, with Cincinnati Children's Hospital Medical Center Review Board as the reviewing IRB. Stanford's IRB is a relying IRB within the sIRB. As foreign institutions, the University of Toronto and The Hospital for Sick Children (SickKids) are overseen by their respective ethics boards. All participants provide signed informed consent. We are committed to open-access publication, so that patients, clinicians and scientists have access to the study data and the signature(s) derived. After findings are published, we will upload a limited data set for sharing with other investigators on applicable repositories.

TRIAL REGISTRATION NUMBER

NCT04285112.

Developmental Mechanisms of CPSP: Clinical Observations and Translational Laboratory Evaluations

Understanding mechanisms that underly the transition from acute to chronic pain and identifying potential targets for preventing or minimizing this progression have specific relevance for chronic postsurgical pain (CPSP). Though it is clear that multiple psychosocial, family, and environmental factors may influence CPSP, this review will focus on parallels between clinical observations and translational laboratory studies investigating the acute and long-term effects of surgical injury on nociceptive pathways. This includes data related to alterations in sensitivity at different points along nociceptive pathways from the periphery to the brain; age- and sex-dependent mechanisms underlying the transition from acute to persistent pain; potential targets for preventive interventions; and the impact of prior surgical injury. Ongoing preclinical studies evaluating age- and sex-dependent mechanisms will also inform comparative efficacy and preclinical safety assessments of potential preventive pharmacological interventions aimed at reducing the risk of CPSP. In future clinical studies, more detailed and longitudinal peri-operative phenotyping with patient- and parent-reported chronic pain core outcomes, alongside more specialized evaluations of somatosensory function, modulation, and circuitry, may enhance understanding of individual variability in postsurgical pain trajectories and improve recognition and management of CPSP.

Early Life Painful Procedures: Long-Term Consequences and Implications for Farm Animal Welfare

Farm animals routinely undergo painful husbandry procedures early in life, including disbudding and castration in calves and goat kids, tail docking and castration in piglets and lambs, and beak trimming in chicks. In rodents, inflammatory events soon after birth, when physiological systems are developing and sensitive to perturbation, can profoundly alter phenotypic outcomes later in life. This review summarizes the current state of research on long-term phenotypic consequences of neonatal painful procedures in rodents and farm animals, and discusses the implications for farm animal welfare. Rodents exposed to early life inflammation show a hypo-/hyper-responsive profile to pain-, fear-, and anxiety-inducing stimuli, manifesting as an initial attenuation in responses that transitions into hyperresponsivity with increasing age or cumulative stress. Neonatal inflammation also predisposes rodents to cognitive, social, and reproductive deficits, and there is some evidence that adverse effects may be passed to offspring. The outcomes of neonatal inflammation are modulated by injury etiology, age at the time of injury and time of testing, sex, pain management, and rearing environment. Equivalent research examining long-term phenotypic consequences of early life painful procedures in farm animals is greatly lacking, despite obvious implications for welfare and performance. Improved understanding of how these procedures shape phenotypes will inform efforts to mitigate negative outcomes through reduction, replacement, and refinement of current practices.

Pain in Preterm Infants: Different Perspectives

In the last decades, there has been a tremendous change in approaching and managing neonates' pain. These changes began with rebutting the previous misconception about neonates' , particularly preterm infants' , pain. The development in neuroimaging has revealed that by 24 weeks of gestation the peripheral nervous system is mature and function fully. Researchers now know that neonates experience pain and premature infants have even lower pain thresholds. Since that time, a mounting amount of literature has addressed the issue of neonatal pain. Many pharmacological and non pharmacological pain reduction strategies have been investigated for their safety and analgesic effectiveness. Many interventions such as nonnutritive sucking (NNS), skin-to-skin contact (SSC), and facilitated tucking are effective in controlling neonates pain.

Maternal separation with neonatal pain influences later-life fear conditioning and somatosenation in male and female rats

Early life adversity, including that which occurs in a medical setting, has been increasingly shown to have lasting consequences on both physical and mental health. In order to understand the lasting effects of early-life adversity, such as that might occur in the neonatal intensive care unit (NICU), several rodent models have been developed including maternal separation, neonatal handling, and repeated needle prick pain. However, in the clinical scenario, these stressors are often combined. Thus, the current study seeks to observe the lasting impacts of both neonatal pain and maternal separation in a rodent model. Rats were separated from their dam for 6 h per day during the first 7 days of life, during which they were subjected to repeated needle prick pain or handling. A separate group was left undisturbed. All rats were subsequently tested for threat processing using a 3-day Pavlovian fear conditioning model and for somatosensation using measures of mechanical and thermal thresholds. Results indicated that rats subjected to maternal separation and pain had enhanced fear conditioning in adolescence as well as displaying a modest age-independent tactile hypersensitivity compared to undisturbed controls. These data show that experiencing combined neonatal pain and maternal separation may create a latent vulnerability to subsequent stressors.

The Long-Term Effects of Neonatal Inflammatory Pain on Cognitive Function and Stress Hormones Depend on the Heterogeneity of the Adolescent Period of Development in Male and Female Rats

Exposure to stress at an early age programs the HPA axis which can lead to cognitive deficits in adults. However, it is not known whether these deficits emerge in adulthood or are expressed earlier in life. The aims of the study were to investigate (1) the immediate effects of early injury-induced stress in one-day-old (P1) and repeated stress on at P1 and P2 rat pups on plasma corticosterone levels; and (2) examine the subsequent long-term effects of this early stress on spatial learning and memory, and stress reactivity in early P26-34 and late P45-53 adolescent male and female rats. Intra-plantar injection of formalin induced prolonged and elevated levels of corticosterone in pups and impaired spatial learning and short- and long-term memory in late adolescent males and long-term memory in early adolescent females. There were sex differences in late adolescence in both learning and short-term memory. Performance on the long-term memory task was better than that on the short-term memory task for all early adolescent male and female control and stressed animals. Short-term memory was better in the late age control rats of both sexes and for formalin treated females as compared with the early age rats. These results are consistent with an impaired function of structures involved in memory (the hippocampus, amygdala, prefrontal cortex) after newborn pain. However, activation of the HPA axis by neonatal pain did not directly correlate with spatial learning and memory outcomes and the consequences of neonatal pain remain are likely multi-determined.

Early post-natal life stress induces permanent adrenocorticotropin-dependent hypercortisolism in male mice

PURPOSE

It has been hypothesized that specific early-life stress (ES) procedures on CD-1 male mice produce diabetes-like alterations due to the failure of negative feedback of glucocorticoid hormone in the pituitary. The aim of this study is to investigate the possible mechanism that leads to this pathological model, framing it in a more specific clinical condition.

METHODS

Metabolic and hypothalamic-pituitary-adrenal-related hormones of stressed mice (SM) have been analyzed immediately after stress procedures (21 postnatal days, PND) and after 70 days of a peaceful (unstressed) period (90 PND). These data have been compared to parameters from age-matched controls (CTR), and mice treated during ES procedures with oligonucleotide antisense for pro-opiomelanocortin (AS-POMC).

RESULTS

At 21 PND, SM presented an increased secretion of hypothalamic CRH and pituitary POMC-derived peptides, as well as higher plasmatic levels of ACTH and corticosterone vs. CTR. At 90 PND, SM showed hyperglycemia, with suppression of hypothalamic CRH, while pituitary and plasmatic ACTH levels, as well as plasma corticosterone, were constantly higher than in CTR. These values are accompanied by a progressive acceleration in gaining total body weight, which became significant vs. CTR at 90 PND together with a higher pituitary weight. Treatment with AS-POMC prevented all hormonal and metabolic alterations observed in SM, both at 21 and 90 PND.

CONCLUSIONS

These findings show that these specific ES procedures affect the negative glucocorticoid feedback in the pituitary, but not in the hypothalamus, suggesting a novel model of ACTH-dependent hypercortisolism that can be prevented by silencing the POMC gene.

A Painful Beginning: Early Life Surgery Produces Long-Term Behavioral Disruption in the Rat

Early life surgery produces peripheral nociceptive activation, inflammation, and stress. Early life nociceptive input and inflammation have been shown to produce long-term processing changes that are not restricted to the dermatome of injury. Additionally stress has shown long-term effects on anxiety, depression, learning, and maladaptive behaviors including substance abuse disorder and we hypothesized that early life surgery would have long-term effects on theses complex behaviors in later life. In this study surgery in the rat hindpaw was performed to determine if there are long-term effects on anxiety, depression, audiovisual attention, and opioid reward behaviors. Male animals received paw incision surgery and anesthesia or anesthesia alone (sham) at postnatal day 6. At 10 weeks after surgery, open field center zone entries were decreased, a measure of anxiety (n = 20) (P = 0.03) (effect size, Cohen's d = 0.80). No difference was found in the tail suspension test as a measure of depression. At 16-20 weeks, attentional performance in an operant task was similar between groups at baseline and decreased with audiovisual distraction in both groups (P < 0.001) (effect size, η² = 0.25), but distraction revealed a persistent impairment in performance in the surgery group (n = 8) (P = 0.04) (effect size, η² = 0.13). Opioid reward was measured using heroin self-administration at 16-24 weeks. Heroin intake increased over time in both groups during 24-h free access (P < 0.001), but was greater in the surgery group (P = 0.045), with a significant interaction between time and treatment (P < 0.001) (effect size, Cohen f ² = 0.36). These results demonstrate long-term disruptions in complex behaviors from surgical incision under anesthesia. Future studies to explore sex differences in early life surgery and the attendant peripheral neuronal input, stress, and inflammation will be valuable to understand emerging learning deficits, anxiety, attentional dysfunction, and opioid reward and their mechanisms. This will be valuable to develop optimal approaches to mitigate the long-term effects of surgery in early life.

Saccharin and naltrexone prevent increased pain sensitivity and impaired long-term memory induced by repetitive neonatal noxious stimulation: role of BDNF and enkephalin

This study aim to examine the hypothesis that repetitive painful stimuli during infancy will alter pain sensitivity and impair learning and memory during adulthood and that saccharin will prevent this through its analgesic effect. Naltrexone is used to examine if saccharin effect is mediated via the endogenous opioid system. Pain in rat pups was induced via needle pricks of the paws on day 1 of their birth (P0). All treatments/ manipulations started on day 1 and continued for 2 weeks. The radial arm water maze (RAWM) test was used to assess learning and memory. Pain threshold through foot-withdrawal response to a hot plate was also assessed. At the end of behavioral tests, animals were killed, hippocampus was dissected, and hippocampal levels of β-endorphin, enkephalin, and brain-derived neurotropic factor (BDNF) were assessed using ELISA. Naltrexone and saccharin combined normalized noxious stimulation induced increased pain sensitivity later in life. Furthermore, naltrexone and saccharin together mitigated the deficiency in learning and memory induced by noxious stimulation. Saccharin treatment prevented reduction in hippocampal enkephalin. Additionally, saccharin prevented hippocampal noxious stimulation induced BDNF decrement. Saccharin prevented long-term memory impairment during adulthood induced by repeated neonatal pain via mechanisms that appear to involve BDNF. Interestingly, naltrexone did not antagonize the effects of saccharin, instead naltrexone augmented saccharin effects.

Antinociceptive effect of vapocoolant medium stream spray on hotplate latency in rat pups

BACKGROUND

Heel sticks account for most blood tests performed in neonates without analgesia because topical local anesthetics are ineffective on heel glabrous skin. We investigated the antinociceptive effect of an alternative topical analgesic, a vapocoolant spray, on hind paw glabrous skin of rat pups. The spray was applied by two methods: method 1 for 4 s at a distance of 8 cm and method 2 for 10 s at a distance of 18 cm.

METHODS

The rat pups were randomized to either method 1 (n = 32) or method 2 (n = 31). Vapocoolant spray was applied to one hind paw randomly, and saline spray was applied to the contralateral paw. The paws were exposed to a hotplate test to measure withdrawal latency time before and 30 s after the spray applications. Additionally, rat pups were tested for tissue toxicity in method 1 (n = 20) and method 2 (n = 20) after application of the vapocoolant spray before heel sticks three times a day for two consecutive days. Analyses of spray and method effects on hotplate withdrawal latency time were determined by nonparametric Wilcoxon tests to assess paired difference between vapocoolant spray and saline spray and to compare difference in medians between the two methods.

RESULTS

Method 1 and method 2 vapocoolant spray applications significantly prolonged the withdrawal latency time compared with saline, a median difference of 0.6 s (IQR 0.1-1.2) for method 1 and 9.5 s (IQR 5.5-10.7) for method 2 (a 15-fold longer latency time with method 2). Method-2 produced significantly longer withdrawal latency time than method 1 with a difference in median time of 8.9 s (CI: 95% 7.3-10.4 s, P < .0001). No histopathological changes were detected.

CONCLUSIONS

Compared with method- 1, the vapocoolant spray in method 2 produced significantly longer withdrawal latency time that is clinically applicable to collecting blood samples after a heel stick.

Sustained release buprenorphine effectively attenuates postoperative hypersensitivity in an incisional pain model in neonatal rats (Rattus norvegicus)

Despite the need for safe and effective postoperative analgesia in neonates, research regarding pain management in neonatal rodents is relatively limited. Here, we investigate whether sustained release buprenorphine (Bup SR) effectively attenuates thermal hypersensitivity in a neonatal rat model of incisional pain. Male and female postnatal day 3 Sprague Dawley rat pups (n = 34) were randomly assigned to one of four treatment groups: 1) saline (control), 0.1 mL, once subcutaneously (SC); 2) buprenorphine HCl (Bup HCl), 0.05 mg/kg, once SC; 3) low dose Bup SR (low-SR), 0.5 mg/kg, once SC; 4) high dose Bup SR (high-SR), 1 mg/kg, once SC. Pups were anesthetized with sevoflurane and a 0.5-cm long skin incision was made over the left lateral thigh. The underlying muscle was dissected and closed using surgical glue. Thermal hypersensitivity testing was performed at 24 h prior to surgery and subsequently at 1, 4, 8, 24, and 48 h post-surgery using an infrared diode laser. Thermal hypersensitivity was attenuated at 1 h post-surgery in the Bup HCl group, while it was attenuated through the entire postoperative period in both low-SR and high-SR groups. This data suggests that a single dose of low-SR (0.5 mg/kg) or high-SR (1 mg/kg) effectively attenuates thermal hypersensitivity for at least 8 h in neonatal rat pups.

Non-pharmaceutical intervention and pain management situation for neonatal analgesia

Neonatal pain management is an important issue which should have great attention. More and more researches have proved that neonates can feel pain when undergoes painful procedures such as vaccination, heel stick, and so on, and it will result in short-term and long-term outcomes. So it is very important to manage neonatal pain. This article summarized some non-pharmaceutical interventions, including sucrose or glucose, non-nutritional sucking (NNS), breastfeeding, facilitated tucking (FT), kangaroo mother care (KMC), swaddling, heel warming, sensorial saturation (SS), and music therapy, which showed obvious effects for neonatal pain. In addition, this article summarized the progress of neonatal pain intervention in various countries and showed that many countries have not paid enough attention to this problem, while some countries have carried out promotion programs for neonatal pain management which give some clinical enlightenment to our country that we need to pay more attention to this problem.

Sensory processing and cortisol at age 4 years: Procedural pain-related stress in children born very preterm

Children born preterm display altered sensory processing, which may manifest as hyper- and/or hypo-sensitivity to sensory information. In this vulnerable population, exposure to neonatal pain-related stress is associated with altered stress regulation, as indexed by alterations in cortisol levels. It is unknown whether sensory processing behaviors are also affected by early life adversity, and whether dysregulated cortisol is related to sensory processing problems in preterm children. We examined relationships between neonatal pain-related stress, sensory processing profiles and cortisol levels at age 4 years, and whether pathways were sex-specific. In a longitudinal prospective cohort study, N = 146 infants born 24-32 weeks gestational age were recruited from BC Women's Hospital, Vancouver, BC, Canada; neonatal factors were collected from daily chart review. At age 4 years, saliva to assay cortisol was collected three times across cognitive assessment (pre-test, during, end) and parents completed the Short Sensory Profile questionnaire. Using generalized linear modeling, independent of other neonatal factors, higher number of invasive procedures (pain/stress) was associated with more sensory processing problems (total, hypo- and hyper-sensitivity) for girls only. After accounting for neonatal factors, greater cortisol output across the assessment was associated with more total sensory processing problems in girls only, and hypersensitivity to sensory input in both boys and girls. Findings suggest that in children born very preterm, how a child responds to sensory input and cortisol reactivity to stress are related but may have different precursors. Girls may be somewhat more susceptible to neonatal pain-related stress exposure in relation to sensory processing at preschool age.

Adult brain activation in response to pain is changed by neonatal painful stimulation according to sex: A manganese-enhanced MRI study

Although it is known that nociceptive stimulation in the first postnatal week in rats is useful to model preterm pain, resulting in activation of specific brain areas, as assessed in vivo using manganese-enhanced magnetic resonance imaging (MEMRI), little is known about its long-term effects and sex specificity. Here we aimed to investigate whether inflammatory pain induced in male and female adult rats modify the pattern of brain activation between animals subjected or not to neonatal pain. For this, Complete Freund's adjuvant (CFA) was injected into the left hind paw of rat pups on postnatal day 1 (P1) or P8 to induce inflammatory response. During adulthood, CFA-treated and control animals were injected with CFA 1 hr prior MRI. MEMRI has the ability to enhance the contrast of selective brain structures in response to a specific stimulus, as the pain. MEMRI responses were consistent with activation of nociceptive pathways and these responses were reduced in animals treated with CFA on P1, but increased in animals treated on P8, mainly in the female group. In agreement, P8 female group showed exacerbated responses in the thermal nociceptive test. Using MEMRI, we conclude that the natural ability of adult rats to recognize and react to pain exposition is modified by neonatal painful exposition, mainly among females.

The role of the spinal cyclooxygenase (COX) for incisional pain in rats at different developmental stages

BACKGROUND

Cyclooxygenase enzymes (COX)-1 and COX-2 are important targets for pain relief after surgery, but the spinal contribution of both isoforms is still unclear, e.g., from a developmental point of view. Here, we studied changes of spinal COX-1 and COX-2 expression and their functional relevance in rats of different ages for pain-related behaviour after incision.

METHODS

Mechanical paw withdrawal thresholds (PWT) were assessed before and after incision and after intrathecal administration (IT) of SC-560 (COX-1 inhibitor) or NS-398 (COX-2 inhibitor) in rats aged 5, 14 and 28 days (P5, P14, P28). Furthermore, spinal expressions of COX m-RNA and proteins were investigated.

RESULTS

In P5 rats, only IT-administered NS-398 but not SC-560 significantly reversed the decreased PWT after incision. In P14 rats, none of the substance modified PWT, and in P28 rats, only SC-560 increased PWT. Spinal COX-2 mRNA and protein were increased in P5 but not in P14 and P28 rats after incision. Whereas COX-2 is located in spinal neurons, COX-1 is mainly found in spinal microglia cells.

CONCLUSION

Our results demonstrate a possible developmental transition from COX-2 to COX-1 activation. Whereas in adult rats spinal COX-1 but not COX-2 is involved in pain-related behaviour after incision, it seems opposite in P5 rats. Interestingly, in P14, neither COX-1 nor COX-2 seems to play a role. This switch may relate to altered neuronal/microglia activation. Our findings indicate specific mechanisms to pain after incision that are age-dependent and may guide further research improving paediatric pain management.

SIGNIFICANCE

Postoperative pain in pediatric patients after surgery is still poorly controlled; this might contribute to long-lasting alteration in the nociceptive system and prolonged chronic pain. Here we show a possible developmental switch in the COX-dependent pathway for nociceptive spinal transmission that may explain why pain management in young children needs to be related to age-dependent mechanisms.

Adrenal function links to early postnatal growth and blood pressure at age 6 in children born extremely preterm

BACKGROUND

Low birth weight in term-born individuals correlates with adverse cardiometabolic outcomes; excess glucocorticoid exposure has been linked to these relationships. We hypothesized that cortisol and adrenal androgens would correlate inversely with birthweight and directly with markers of cardiometabolic risk in school-aged children born extremely preterm; further, preterm-born would have increased cortisol and adrenal androgens compared to term-born children.

METHODS

Saliva samples were obtained at age 6 from 219 preterm-born children followed since birth and 40 term-born children and analyzed for dehydroepiandrosterone (DHEA) and cortisol. Cortisol was also measured at home (awakening, 30' later, evening).

RESULTS

For preterm-born children, cortisol and DHEA correlated inversely with weight and length Z-scores at 36 weeks PMA and positively with systolic BP. DHEA was higher in preterm-born than term-born children (boys p < 0.01; girls p = 0.04). Cortisol was similar between preterm-born and term-born at study visit; however, preterm-born children showed a blunted morning cortisol. In term-born children, DHEA correlated with BMI (p = 0.04), subscapular, and abdominal skinfold thicknesses (both p < 0.01).

CONCLUSION

Cortisol and DHEA correlated inversely with early postnatal growth and directly with systolic BP in extremely preterm-born children, suggesting perinatal programming. Blunted morning cortisol may reflect NICU stress, as seen after other adverse childhood experiences (ACEs).

Long-term effects of neonatal pain

Pain experienced during neonatal intensive care management can influence neurodevelopmental outcome and the somatosensory and/or emotional components of pain response in later life. Alterations in biological factors (e.g. peripheral and central somatosensory function and modulation, brain structure and connectivity) and psychosocial factors (e.g. gender, coping style, mood, parental response) that influence pain have been identified in children and young adults born very preterm or extremely preterm. Earlier gestational age at birth and cumulative pain exposure from tissue-breaking procedures and/or neonatal surgery influence the degree of change. In neonatal rodents, repeated needle insertion or hindpaw incision identify developmentally-regulated and activity-dependent long term alterations in nociceptive processing, and the efficacy of novel or current analgesic interventions can be compared. As prior neonatal experience and sex may influence current pain experience or the risk of persistent pain, these factors should be considered within the biopsychosocial assessment and formulation of pain in later life.

Early and late anti nociceptive effects of sucrose on neonatal inflammatory pain in rats: Comparison to a non-steroidal anti-inflammatory drug

Management of neonatal pain is not only ethical but is also essential. Barriers to pain management in infants include lack of safe and effective medications and fear of adverse effects of conventional pain medications. Sweet solutions given intraorally have been shown to reduce pain behaviors and associated symptoms. Sucrose and other sweet solutions are being increasingly used at the NICUs and immunization clinics. Sucrose for mild invasive procedures is effective and safe for those procedures that need to be repeated multiple times during the day. Only few studies examine the efficacy of sucrose for the management of inflammatory pain during infancy. In this study, Complete Freund's Adjuvant (CFA) was used to induce inflammation in 5-day-old rat pups; CFA also produces inflammation that lasts for more than a day, thus can also be a model for chronic pain. Sucrose or ibuprofen was given to subset of pups shortly after CFA intraplantar injections. Thermal as well as mechanical pain sensitivity was assessed on subsequent days as well as during adolescence and early adulthood. Sucrose and ibuprofen were both effective in preventing hyperalgesia and allodynia produced by CFA. Interestingly, sucrose was even more effective than ibuprofen, and the analgesic effects continued further to adolescence and adult life of the rats. Thus, and according to the results of this study, sucrose seems to be just as effective for inflammatory pain as Ibuprofen. In addition, sucrose protects against later-in-life hypersensitivity consequences to neonatal pain.

Physiology of Stress and Use of Skin-to-Skin Care as a Stress-Reducing Intervention in the NICU

Advances in neonatal care have allowed for the increasing survival of critically ill infants. These infants experience significant stress related to painful procedures and physical separation from their parents. The purpose of this article is to describe the physiologic stress mechanisms that contribute to mortality and morbidity in infants in the NICU and the physiologic mechanisms by which skin-to-skin care (SSC) acts on the stress response system. Findings from current literature supporting the use of SSC and barriers and facilitators to implementation are reviewed. SSC is a safe and effective intervention to reduce stress for infants and their parents. Nurses play a key role in facilitating SSC to optimize outcomes of care in the NICU.

Glucocorticoid receptor single nucleotide polymorphisms are associated with acute crisis pain in sickle cell disease

AIM

Pain in sickle cell disease patients is heterogeneous and genetic polymorphisms may predispose an individual to varied vulnerability to painful events. We studied the association of SNPs in the glucocorticoid receptor gene (NR3C1) with pain in sickle cell disease.

METHOD

Acute pain was scored as the number of utilizations due to crisis pain in a 12-month period. Chronic pain was calculated as the Composite Pain Index score.

RESULTS & CONCLUSION

rs33389 T allele (IRR = 1.53, p = 0.014 additive; IRR = 1.64, p = 0.011 recessive), rs2963155 G allele (IRR = 1.80, p < 0.001 additive; IRR = 2.25, p = 0.021 dominant; IRR = 2.07, p < 0.001 recessive) and rs9324918 C allele (IRR = 1.43, p = 0.021 additive) were associated with higher utilization rates, indicating the potential contribution of NR3C1 polymorphisms to acute pain heterogeneity in sickle cell disease.

Trauma-informed care in the newborn intensive care unit: promoting safety, security and connectedness

Both babies and their parents may experience a stay in the newborn intensive care unit (NICU) as a traumatic or a 'toxic stress,' which can lead to dysregulation of the hypothalamic-pituitary-adrenal axis and ultimately to poorly controlled cortisol secretion. Toxic stresses in childhood or adverse childhood experiences (ACEs) are strongly linked to poor health outcomes across the lifespan and trauma-informed care is an approach to caregiving based on the recognition of this relationship. Practitioners of trauma-informed care seek to understand clients' or patients' behaviors in light of previous traumas they have experienced, including ACEs. Practitioners also provide supportive care that enhances the client's or patient's feelings of safety and security, to prevent their re-traumatization in a current situation that may potentially overwhelm their coping skills. This review will apply the principles of trauma-informed care, within the framework of the Polyvagal Theory as described by Porges, to care for the NICU baby, the baby's family and their professional caregivers, emphasizing the importance of social connectedness among all. The Polyvagal Theory explains how one's unconscious awareness of safety, danger or life threat (neuroception) is linked through the autonomic nervous system to their behavioral responses. A phylogenetic hierarchy of behaviors evolved over time, leveraging the mammalian ventral or 'smart' vagal nucleus into a repertoire of responses promoting mother-baby co-regulation and the sense of safety and security that supports health and well-being for both members of the dyad. Fostering social connectedness that is mutual and reciprocal among parents, their baby and the NICU staff creates a critical buffer to mitigate stress and improve outcomes of both baby and parents. Using techniques of trauma-informed care, as explained by the Polyvagal Theory, with both babies and their parents in the NICU setting will help to cement a secure relationship between the parent-infant dyad, redirecting the developmental trajectory toward long-term health and well-being of the baby and all family members.

Microglia in health and pain: impact of noxious early life events

NEW FINDINGS

What is the topic of this review? This review discusses the origins and development of microglia, and how stress, pain or inflammation in early life disturbs microglial function during critical developmental periods, leading to altered pain sensitivity and/or increased risk of chronic pain in later life. What advances does it highlight? We highlight recent advances in understanding how disrupted microglial function impacts the developing nervous system and the consequences for pain processing and susceptibility for development of chronic pain in later life. The discovery of microglia is accredited to Pío del Río-Hortega, who recognized this 'third element' of CNS cells as being morphologically distinct from neurons and astrocytes. For decades after this finding, microglia were altogether ignored or relegated as simply being support cells. Emerging from virtual obscurity, microglia have now gained notoriety as immune cells that assume a leading role in the development, maintenance and protection of a healthy CNS. Pioneering studies have recently shed light on the origins of microglia, their role in the developing nervous system and the complex roles they play beyond the immune response. These studies reveal that altered microglial function can have a profoundly negative impact on the developing brain and may be a determinant in a range of neurodevelopmental disorders and neurodegenerative diseases. The realization that aberrant microglial function also critically underlies chronic pain, a debilitating disorder that afflicts over 1.5 billion people worldwide, was a major conceptual leap forward in the pain field. Adding to this advance is emerging evidence that early life noxious experiences can have a long-lasting impact on central pain processing and adult pain sensitivity. With microglia now coming of age, in this review we examine the association between adverse early life events, such as stress, injury or inflammation, and the influence of sex differences, on the role of microglia in pain physiology in adulthood.

Optimal reference genes for RT-qPCR normalization in the newborn

It is difficult to identify reliable reference genes for transcriptomic analyses in biofluids such as saliva. This situation is particularly relevant for the newborn population, where rapid development is associated with dynamic changes in gene expression. Real-time gene expression monitoring holds great promise for elucidating disrupted pathways that result in morbidities unique to this population, such as retinopathy of prematurity, but its impact depends on identifying stable and consistently expressed genes across a wide range of gestational ages. We extracted total RNA from 400 neonatal saliva samples (postconceptional ages: 32 5/7 to 48 2/7 weeks), converted it to cDNA, and pre-amplified and analyzed it by qPCR for three commonly used reference genes, ACTB, GAPDH, and YWHAZ. Relative quantification was determined using the Δ Ct method. Data were analyzed as a whole and also stratified by age and sex. Descriptive statistics and homogeneity of variance were performed to identify optimal reference genes. Data analyzed from all ages and both sexes showed significant expression variation for ACTB, while GAPDH and YWHAZ showed greater stability. Male infants exhibited increased expression variation compared to females for ACTB, but neither GAPDH nor YWHAZ showed significant variance for either sex. We suggest that ACTB is an unreliable reference gene for the newborn population. Males showed significantly more variation in ACTB expression compared to females, which suggests a sex-specific developmental role for this biomarker. By contrast, GAPDH and YWHAZ were less variable and therefore preferable for use in neonates. Our findings may improve the use of reference genes for the RT-qPCR platform in the newborn over a wide range of gestational ages, thereby minimizing the likelihood of erroneous interpretation of gene expression during rapid growth, development, and differentiation.

Procedural Pain Scale Evaluation (PROPoSE) study: protocol for an evaluation of the psychometric properties of behavioural pain scales for the assessment of procedural pain in infants and children aged 6-42 months

INTRODUCTION

Infants and children are frequently exposed to painful medical procedures such as immunisation, blood sampling and intravenous access. Over 40 scales for pain assessment are available, many designed for neonatal or postoperative pain. What is not well understood is how well these scales perform when used to assess procedural pain in infants and children.

AIM

The aim of this study was to test the psychometric and practical properties of the Face, Legs, Activity, Cry and Consolability (FLACC) scale, the Modified Behavioural Pain Scale (MBPS) and the Visual Analogue Scale (VAS) observer pain scale to quantify procedural pain intensity in infants and children aged from 6-42 months to determine their suitability for clinical and research purposes.

METHODS AND ANALYSIS

A prospective observational non-interventional study conducted at a single centre. The psychometric and practical performance of the FLACC scale, MBPS and the VAS observer pain scale and VAS observer distress scale used to assess children experiencing procedural pain will be assessed. Infants and young children aged 6-42 months undergoing one of four painful and/or distressing procedures were recruited and the procedure digitally video recorded. Clinicians and psychologists will be recruited to independently apply the scales to these video recordings to establish intrarater and inter-rater reliability, convergent validity responsiveness and specificity. Pain score distributions will be presented descriptively; reliability will be assessed using the intraclass correlation coefficient and Bland-Altman plots. Spearman correlations will be used to assess convergence and linear mixed modelling to explore the responsiveness of the scales to pain and their capacity to distinguish between pain and distress.

ETHICS AND DISSEMINATION

Ethical approval was provided by the Royal Children's Hospital Human Research Ethics Committee, approval number 35220B. The findings of this study will be disseminated via peer-reviewed journals and presented at international conferences.

Chemotherapy-Induced Neuropathy in Cancer Survivors

CONTEXT

Evidence suggests that chemotherapy-induced neuropathy (CIN) is a significant problem for cancer survivors. However, a detailed phenotypic characterization of CIN in cancer survivors is not available.

OBJECTIVES

To evaluate between-group differences in demographic and clinical characteristics, as well as in measures of sensation, function, and postural control, in a sample of cancer survivors who received a platinum and/or a taxane-based CTX regimen and did (n = 426) and did not (n = 197) develop CIN.

METHODS

Survivors completed self-report questionnaires and underwent objective testing (i.e., light touch, pain sensation, cold sensation, vibration, muscle strength, grip strength, Purdue Pegboard test, Timed Get Up and Go test, Fullerton Advanced Balance test). Parametric and nonparametric statistics were used to compare between-group differences in study outcomes.

RESULTS

Of the 426 survivors with CIN, 4.9% had CIN only in their upper extremities, 27.0% only in their lower extremities, and 68.1% in both their upper and lower extremities. Demographic and clinical characteristics associated with CIN included the following: older age, lower annual income, higher body mass index, a higher level of comorbidity, being born prematurely, receipt of a higher cumulative dose of chemotherapy, and a poorer functional status. Survivors with CIN had worse outcomes for all of the following objective measures: light touch, pain, temperature, vibration, upper and lower extremity function, and balance.

CONCLUSIONS

This study is the first to provide a detailed phenotypic characterization of CIN in cancer survivors who received a platinum and/or a taxane compound. These data can serve as a benchmark for future studies of CIN in cancer survivors.

The flexion withdrawal reflex increases in premature infants at 22-26 weeks of gestation due to changes in spinal cord excitability

Aim

Our aim was to study the development of the cutaneous flexion withdrawal reflex among premature infants admitted to the neonatal intensive care unit of the Children's Hospital, University of Cologne, in 2013.

Methodology

This longitudinal cohort study explored the development of spinal cord excitability of 19 premature infants born at 22–26 weeks of gestation. We performed five investigations per subject and studied changes in the reflex threshold with increasing postnatal age at different behavioural states. The premature infants were stimulated with von Frey filaments on the plantar surface of the foot near the first metatarsophalangeal joint during the first 3 days of life and at postnatal ages of 10–14 days, 21–28 days, 49–59 days and a corrected gestational age of 37–40 weeks.

Results

The mean gestational age of the premature infants included in the study was 24 weeks. Premature infants with a gestational age of less than 26 weeks presented a flexion withdrawal reflex with a low threshold (0.5–2.85 milli‐Newton) in the first 72 hours of life.

Conclusion

The flexion withdrawal reflex among premature infants born at less than 26 weeks showed a continuous threshold increase with increasing postnatal age, reflecting changes in spinal cord excitability.

The impact of cumulative pain/stress on neurobehavioral development of preterm infants in the NICU

BACKGROUND

Vulnerable preterm infants experience repeated and prolonged pain/stress stimulation during a critical period in their development while in the neonatal intensive care unit (NICU). The contribution of cumulative pain/stressors to altered neurodevelopment remains unclear. The study purpose was to investigate the impact of early life painful/stressful experiences on neurobehavioral outcomes of preterm infants in the NICU.

METHODS

A prospective exploratory study was conducted with fifty preterm infants (28 0/7-32 6/7weeks gestational age) recruited at birth and followed for four weeks. Cumulative pain/stressors (NICU Infant Stressor Scale) were measured daily and neurodevelopmental outcomes (NICU Network Neurobehavioral Scale) were examined at 36-37weeks post-menstrual age. Data analyses were conducted on the distribution of pain/stressors experienced over time and the linkages among pain/stressors and neurobehavioral outcomes.

RESULTS

Preterm infants experienced a high degree of pain/stressors in the NICU, both in numbers of daily acute events (22.97±2.30 procedures) and cumulative times of chronic/stressful exposure (42.59±15.02h). Both acute and chronic pain/stress experienced during early life significantly contributed to the neurobehavioral outcomes, particularly in stress/abstinence (p<0.05) and habituation responses (p<0.01), meanwhile, direct breastfeeding and skin-to-skin holding were also significantly associated with habituation (p<0.01-0.05).

CONCLUSION

Understanding mechanisms by which early life experience alters neurodevelopment will assist clinicians in developing targeted neuroprotective strategies and individualized interventions to improve infant developmental outcomes.

Long-Term Effects of Chronic Buspirone during Adolescence Reduce the Adverse Influences of Neonatal Inflammatory Pain and Stress on Adaptive Behavior in Adult Male Rats

Neonatal pain and stress induce long-term changes in pain sensitivity and behavior. Previously we found alterations in pain sensitivity in adolescent rats exposed to early-life adverse events. We tested whether these alterations have long-lasting effects and if those effects can be improved by the 5-hydroxytryptamine 1A (5-HT1A) receptor agonist buspirone injected chronically during the adolescent period. This study investigates: (1) effects of inflammatory pain (the injection of formalin into the pad of a hind paw) or stress (short maternal deprivation-isolation, MI), or their combination in 1-2-day-old rats on the adult basal pain, formalin-induced pain, anxiety and depression; (2) effects of adolescent buspirone in adult rats that experienced similar early-life insults. Changes in nociceptive thresholds were evaluated using the hot plate (HP) and formalin tests; levels of anxiety and depression were assessed with the elevated plus maze and forced swim tests respectively. Both neonatal painful and stressful treatments induced long-term alterations in the forced swim test. Other changes in adult behavioral responses were dependent on the type of neonatal treatment. There was a notable lack of long-term effects of the combination of early inflammatory pain and stress of MI on the pain responses, anxiety levels or on the effects of adolescent buspirone. This study provides the first evidence that chronic injection of buspirone in adolescent rats alters antinociceptive and anxiolytic effects limited to adult rats that showed behavioral alterations induced by early-life adverse treatments. These data highlight the role of 5-HT1A receptors in long-term effects of neonatal inflammatory pain and stress of short MI on adaptive behavior and possibility of correction of the pain and psychoemotional behavior that were altered by adverse pain/stress intervention using buspirone during critical adolescent period.

Why Harmless Sensations Might Hurt in Individuals with Chronic Pain: About Heightened Prediction and Perception of Pain in the Mind

In individuals with chronic pain harmless bodily sensations can elicit anticipatory fear of pain resulting in maladaptive responses such as taking pain medication. Here, we aim to broaden the perspective taking into account recent evidence that suggests that interoceptive perception is largely a construction of beliefs, which are based on past experience and that are kept in check by the actual state of the body. Taking a Bayesian perspective, we propose that individuals with chronic pain display a heightened prediction of pain [prior probability p(pain)], which results in heightened pain perception [posterior probability p(pain|sensation)] due to an assumed link between pain and a harmless bodily sensation [p(sensation|pain)]. This pain perception emerges because their mind infers pain as the most likely cause for the sensation. When confronted with a mismatch between predicted pain and a (harmless bodily) sensation, individuals with chronic pain try to minimize the mismatch most likely by active inference of pain or alternatively by an attentional shift away from the sensation. The active inference results in activities that produce a stronger sensation that will match with the prediction, allowing subsequent perceptual inference of pain. Here, we depict heightened pain perception in individuals with chronic pain by reformulating and extending the assumptions of the interoceptive predictive coding model from a Bayesian perspective. The review concludes with a research agenda and clinical considerations.

Intraocular pressure in infants and its association with hormonal changes with vaginal birth versus cesarean section

To investigate cord arterial blood sample and the relationship between birth stress and intraocular pressure in infants at 5 min after delivery. The IOP measurements were taken using Tonopen-Avia tonometer to 158 newborns (158 eyes) at 5th min after birth, in a university hospital. Cord blood was collected within 3 min after delivery. Intraocular pressure, gender, gestation period, mode of delivery, and birth weight of newborns were noted from medical records. Sixty-two babies were delivered by normal vaginal delivery (NVD) and 96 by cesarian section (C/S). Mean IOP of NVD and C/S groups were 19.56 ± 3.84 and 17.42 ± 3.50, respectively. There was significant difference of mean IOP between two groups. (p < 0.001) There were significant differences between two groups regarding APGAR score (p < 0.001) and cord blood adrenaline (p = 0.003), noradrenaline (p = 0.008), and cortisol (p < 0.001) levels. There was no difference between infant corneal thickness measurements (p = 0.698). In correlation analyses, there is a strong negative correlation between the labor type and postpartum measurements except corneal thickness. Correlation analyses of the 5th min intraocular pressure of the groups individually revealed significant correlation in the NVD group. The conclusion is that the intraocular pressure of newborn infants was higher in NVD delivery compare to C/S. Blood hormonal changes in different anesthesia types and physical stress was thought as the main reason of this result.

Exposure to Early Life Pain: Long Term Consequences and Contributing Mechanisms

From an evolutionary perspective, adaptations of an organism to its early environment are essential for survival. The occurrence of early life perturbation, coincident with increased developmental plasticity, provides a unique opportunity for such adaptations to become programmed and persist throughout life. However, adaptations that are beneficial to maintaining homeostasis in one's early environment may result in extreme response strategies that confer vulnerability or dysfunction later in life. This review summarizes recent findings in human and animal studies demonstrating that early life pain results in a hypo-/hyper-sensitive phenotype in response to acute and persistent pain and stress later in life. Changes in cognition and immune function in response to early life pain have also been observed. Recent data on the neural mechanisms underlying these long-term changes are discussed, as well as potential strategies to minimize the impact of early life pain.