Early life opioid exposure and potential long-term effects

Treatment for Neonatal Abstinence Syndrome using Nonpharmacological Interventions

OBJECTIVE

 Management of neonatal abstinence syndrome includes nonpharmacological interventions, but their effectiveness may not be verified before implemented. The objective of this study is to evaluate the effectiveness of a type of bassinet in the treatment of infants with neonatal abstinence syndrome.

STUDY DESIGN

 This is a retrospective observational cohort study. Study setting involved a 24-bed open-bay Level III neonatal intensive care unit located in a metropolitan academic trauma facility. Participant inclusion criteria involved prenatally opioid-exposed infants ≥ 35 weeks with confirmed maternal opioid urine toxicology, required pharmacological treatment for withdrawal symptoms, and were admitted to the neonatal intensive care unit. Three subsets of study participants were analyzed over three different time periods: Group 1 were infants admitted during 2019 without nonpharmacological intervention, Group 2 who were admitted from September 2021 to February 2022 and received nonpharmacological interventions, and Group 3 included those admitted from February 2022 to March 2023 who received the same interventions as Group 2 but were managed in bassinets being used in other local facilities for neonatal abstinence syndrome.

RESULTS

 Group 3 had significant increases in length of stay compared with Group 1 (p = 0.006) and Group 2 (p = 0.013). Group 3 had a significantly greater length of treatment than Group 1 (p = 0.041) and a significantly higher total mg/kg morphine exposure than Group 1 (p = 0.006).

CONCLUSION

 Addition of the bassinet for nonpharmacological management of infants with neonatal abstinence syndrome appeared to prolong length of stay, length of treatment, and increase total mg/kg morphine exposure. As a retrospective nonrandomized study, weakness of low certainty of causality is of concern but findings strongly warrant further research before devices such as the bassinet used in this study are adopted for routine neonatal abstinence syndrome care.

KEY POINTS

· Special bassinets are promoted to enhance sleep and decrease agitation.. · Such bassinets may assist infants undergoing drug withdrawal.. · Study of the bassinet failed to show benefit to this population..

Neonatal Abstinence Syndrome and Corresponding Pharmacotherapy Approaches from 2 University-affiliated Neonatal Intensive Care Units in Puerto Rico (2018-2020)

OBJECTIVE

Neonatal abstinence syndrome (NAS) is a set of drug withdrawal symptoms suffered by neonates exposed to drugs in utero. Several studies have widely described NAS incidence and treatment approach; however, little is known regarding the incidence and manifestations of this disease in Puerto Rico (PR). The principal aim of this study was to describe NAS incidence in the neonatal units of hospitals affiliated with the University of PR in terms of occurrence, clinical manifestations, and treatment approaches.

METHODS

Our study evaluated the medical records of NAS babies diagnosed from 2018 through 2020 at 2 hospitals affiliated with the University of PR Medical Sciences Campus. Descriptive and inferential statistics were employed to analyze trends.

RESULTS

We identified 12 neonates diagnosed with NAS, 5 with low birthweights (<2500 g); for a NAS incidence of 2 cases per 1000 admitted for the 3 years of recollected data. The urine toxicology results revealed that 9 had experienced intrauterine polydrug exposure. Phenobarbital loading dose were determined on the day of diagnosis (indicated by Finnegan score). The first manifestation of NAS symptoms varied: 8 neonates showed symptoms within 48 hours after birth, whereas 4 had withdrawal symptoms within 72-120 hours of their births. Differences between dosing practices and guidelines were observed, ranging from a 0.69% to a 25% difference during treatment initiation.

CONCLUSION

Further research on the incidence of NAS in PR (national level) is needed for a deeper understanding that we hope will lead to the development of enhanced treatment protocols in PR.

Maternal care behavior and physiology moderate offspring outcomes following gestational exposure to opioids

The opioid epidemic has resulted in a drastic increase in gestational exposure to opioids. Opioid-dependent pregnant women are typically prescribed medications for opioid use disorders ("MOUD"; e.g., buprenorphine [BUP]) to mitigate the harmful effects of abused opioids. However, the consequences of exposure to synthetic opioids, particularly BUP, during gestation on fetal neurodevelopment and long-term outcomes are poorly understood. Further, despite the known adverse effects of opioids on maternal care, many preclinical and clinical studies investigating the effects of gestational opioid exposure on offspring outcomes fail to report on maternal care behaviors. Considering that offspring outcomes are heavily dependent upon the quality of maternal care, it is important to evaluate the effects of gestational opioid exposure in the context of the mother-infant dyad. This review compares offspring outcomes after prenatal opioid exposure and after reduced maternal care and integrates this information to potentially identify common underlying mechanisms. We explore whether adverse outcomes after gestational BUP exposure are due to direct effects of opioids in utero, deficits in maternal care, or a combination of both factors. Finally, suggestions for improving preclinical models of prenatal opioid exposure are provided to promote more translational studies that can help to improve clinical outcomes for opioid-dependent mothers.

Perigestational Opioid Exposure Alters Alcohol-Driven Reward Behaviors in Adolescent Rats

Every fifteen minutes, a baby is born in the U.S. experiencing neonatal opioid withdrawal syndrome (NOWS). Since 2004, the rate of NOWS has increased 7-fold. Clinical studies have established intrauterine exposure to drugs of abuse as a risk factor for adverse health outcomes in adult life, including the propensity for future illicit drug use. Despite extensive knowledge about common mechanisms of action in the neural circuitry that drives opioid and alcohol reward, there is little data on the risks that those born with NOWS face regarding alcohol use later in life. Here, we investigate the impact of perigestational opioid exposure (POE) on the mesolimbic reward system of male and female Sprague Dawley rats at postnatal and adolescent ages. Our laboratory has developed a clinically relevant model for morphine exposure spanning pre-conception to the first week of life. Using this model, we found that POE increased alcohol consumption in female rats under noncontingent conditions, and inversely, reduced alcohol consumption in both male and female rats during operant conditioning sessions. Operant responding was also reduced for sucrose, suggesting that the impact of POE on reward-seeking behaviors is not limited to drugs of abuse. Expression of µ-opioid receptors was also significantly altered in the nucleus accumbens and medial habenula, regions previously shown to play a significant role in reward/aversion circuitry.

Significance Statement

Early life exposure to opioids is known to alter future drug behavior in rats. In the present study, female rats exposed to morphine via their mothers throughout and after pregnancy exhibited increased alcohol consumption when allowed to consume freely. During operant conditioning, however, male and female rats exposed to gestational morphine decreased consumption of alcohol as well as sucrose. We also observed that gestational morphine exposure altered µ-opioid receptor expression in reward-related brain regions. Our study provides the first evidence of changes in alcohol-directed reward behavior in a gestational opioid exposure rat model.

Prenatal Morphine Exposure Increases Cardiovascular Disease Risk and Programs Neurogenic Hypertension in the Adult Offspring

BACKGROUND

The opioid overdose and opioid use disorder epidemics are concomitant with increased metabolic and CVD risk. Although opioid use disorder causes adverse pregnancy outcomes, the offspring's cardiovascular health is understudied. We hypothesized that offspring exposed to in utero morphine exposure (IUME) would show increased CVD risk factors and endogenous opioid system dysregulation.

METHODS

Sprague Dawley dams were treated with saline (vehicle, n=10) or escalating doses of morphine (5-20 mg/kg per day, SC, n=10) during gestation. Cardiovascular and metabolic parameters were assessed in adult offspring.

RESULTS

Litter size and pups' birth weight were not different in response to IUME. Female and male IUME offspring showed reduced body length at birth (P<0.05) and body weight from weeks 1 to 3 of life (P<0.05), followed by a catch-up growth effect. By week 16, female and male IUME rats showed reduced tibia length (P<0.05) and fat mass. IUME increases the mean arterial pressure and the depressor response to mecamylamine (5 mg/kg per day, IP) induced by IUME were abolished by a chronic treatment with an alpha-adrenergic receptor blocker (prazosin; 1 mg/kg per day, IP). Although circulating levels of angiotensin peptides were similar between groups, IUME exacerbated maximal ex vivo Ang (angiotensin) II-induced vasoconstriction (P<0.05) and induced endothelial dysfunction in a sex-specific manner (P<0.05). Proenkephalin, an endogenous opioid peptide that lowers blood pressure and sympathetic-mediated vasoconstriction, showed reduced mRNA expression in the heart, aorta, and kidneys from morphine versus vehicle group (P<0.05).

CONCLUSIONS

Among the effects of IUME, neurogenic hypertension, vascular dysfunction, and metabolic dysfunction could be associated with the dysregulation of the endogenous opioid system.

Buprenorphine reduces somatic withdrawal in a mouse model of early-life morphine exposure

The rising prevalence of early-life opioid exposure has become a pressing public health issue in the U.S. Neonates exposed to opioids in utero are at risk of experiencing a constellation of postpartum withdrawal symptoms commonly referred to as neonatal opioid withdrawal syndrome (NOWS). Buprenorphine (BPN), a partial agonist at the mu-opioid receptor (MOR) and antagonist at the kappa-opioid receptor (KOR), is currently approved to treat opioid use disorder in adult populations. Recent research suggests that BPN may also be effective in reducing withdrawal symptoms in neonates who were exposed to opioids in utero. We sought to determine whether BPN attenuates somatic withdrawal in a mouse model of NOWS. Our findings indicate that the administration of morphine (10mg/kg, s.c.) from postnatal day (PND) 1-14 results in increased somatic symptoms upon naloxone-precipitated (1mg/kg, s.c.) withdrawal. Co-administration of BPN (0.3mg/kg, s.c.) from PND 12-14 attenuated symptoms in morphine-treated mice. On PND 15, 24h following naloxone-precipitated withdrawal, a subset of mice was examined for thermal sensitivity in the hot plate test. BPN treatment significantly increased response latency in morphine-exposed mice. Lastly, neonatal morphine exposure elevated mRNA expression of KOR, and reduced mRNA expression of corticotropin-releasing hormone (CRH) in the periaqueductal gray when measured on PND 14. Altogether, this data provides support for the therapeutic effects of acute low-dose buprenorphine treatment in a mouse model of neonatal opioid exposure and withdrawal.

Developmental Brain Injury and Social Determinants of Health: Opportunities to Combine Preclinical Models for Mechanistic Insights into Recovery

Epidemiological studies show that social determinants of health are among the strongest factors associated with developmental outcomes after prenatal and perinatal brain injuries, even when controlling for the severity of the initial injury. Elevated socioeconomic status and a higher level of parental education correlate with improved neurologic function after premature birth. Conversely, children experiencing early life adversity have worse outcomes after developmental brain injuries. Animal models have provided vital insight into mechanisms perturbed by developmental brain injuries, which have indicated directions for novel therapeutics or interventions. Animal models have also been used to learn how social environments affect brain maturation through enriched environments and early adverse conditions. We recognize animal models cannot fully recapitulate human social circumstances. However, we posit that mechanistic studies combining models of developmental brain injuries and early life social environments will provide insight into pathways important for recovery. Some studies combining enriched environments with neonatal hypoxic injury models have shown improvements in developmental outcomes, but further studies are needed to understand the mechanisms underlying these improvements. By contrast, there have been more limited studies of the effects of adverse conditions on developmental brain injury extent and recovery. Uncovering the biological underpinnings for early life social experiences has translational relevance, enabling the development of novel strategies to improve outcomes through lifelong treatment. With the emergence of new technologies to analyze subtle molecular and behavioral phenotypes, here we discuss the opportunities for combining animal models of developmental brain injury with social construct models to deconvolute the complex interactions between injury, recovery, and social inequity.

Comparisons of stress-related neuronal activation induced by restraint in adult male rat offspring with prenatal exposure to buprenorphine, methadone, or morphine

Prenatal opioid exposure may impede the development of adaptive responses to environmental stimuli by altering the stress-sensitive brain circuitry located at the paraventricular nucleus of the hypothalamus (PVH) and locus coeruleus (LC). Corticotropin-releasing factor (CRF) released from neurons in the PVH has emerged as a key molecule to initiate and integrate the stress response. Methadone (Meth) and buprenorphine (Bu) are two major types of synthetic opioid agonists for first-line medication-assisted treatment of opioid (e.g., morphine, Mor) use disorder in pregnant women. No studies have compared the detrimental effects of prenatal exposure to Meth versus Bu on the stress response of their offspring upon reaching adulthood. In this study, we aimed to compare stress-related neuronal activation in the PVH and LC induced by restraint (RST) stress in adult male rat offspring with prenatal exposure to the vehicle (Veh), Bu, Meth, or Mor. CFos-immunoreactive cells were used as an indicator for neuronal activation. We found that RST induced less neuronal activation in the Meth or Mor exposure groups compared with that in the Bu or Veh groups; no significant difference was detected between the Bu and Veh exposure groups. RST-induced neuronal activation was completely prevented by central administration of a CRF receptor antagonist (α-helical CRF_9-41, 10 μg/3 μL) in all exposure groups, suggesting the crucial role of CRF in this stress response. In offspring without RST, central administration of CRF (0.5 μg/3 μL)-induced neuronal activation in the PVH and LC. CRF-induced neuronal activation was lessened in the Meth or Mor exposure groups compared with that in the Bu or Veh groups; no significant difference was detected between the Bu and Veh exposure groups. Moreover, RST- or CRF-induced neuronal activation in the Meth exposure group was comparable with that in the Mor exposure group. Further immunohistochemical analysis revealed that the Meth and Mor exposure groups displayed less CRF neurons in the PVH of offspring with or without RST compared with the Bu or Veh groups. Thus, stress-induced neuronal activation in the PVH and LC was well preserved in adult male rat offspring with prenatal exposure to Bu, but it was substantially lessened in those with prenatal exposure to Meth or Mor. Lowered neuronal activation found in the Meth or Mor exposure groups may be, at least in part, due to the reduction in the density of CRF neurons in the PVH.

Intravenous acetaminophen for postoperative pain control after open abdominal and thoracic surgery in pediatric patients: a systematic review and meta-analysis

Pediatric opioid exposure increases short- and long-term adverse events (AE). The addition of intravenous acetaminophen (IVA) to pediatric pain regimes to may reduce opioids but is not well studied postoperatively. Our objective was to quantify the impact of IVA on postoperative pain, opioid use, and AEs in pediatric patients after major abdominal and thoracic surgery. Medline, Embase, CINAHL, Web of Science, and Cochrane Library were searched systematically for randomized controlled trials (RCTs) comparing IVA to other modalities. Five RCTs enrolling 443 patients with an average age of 2.12 years (± 2.81) were included. Trials comparing IVA with opioids to opioids alone were meta-analyzed. Low to very low-quality evidence demonstrated equivalent pain scores between the groups (-0.23, 95% CI -0.88 to 0.40, p 0.47) and a reduction in opioid consumption (-1.95 morphine equivalents/kg/48 h, 95% CI -3.95 to 0.05, p 0.06) and minor AEs (relative risk 0.39, 95% CI 0.11 to 1.43, p 0.15). We conclude that the addition of IVA to opioid-based regimes in pediatric patients may reduce opioid use and minor AEs without increasing postoperative pain. Given the certainty of evidence, further research featuring patient-important outcomes and prolonged follow-up is necessary to confirm these findings.

Association of Pre-procedural Anxiety with Procedure-related Pain During Outpatient Pediatric Burn Care: A Pilot Study

The relationship between preprocedural anxiety and pain is not clear but has the potential to change the way pediatric patients need to be cared for prior to burn procedures. Using results from our recent randomized clinical trial among outpatient burn patients (n=90) age 6-17 years, the objective of this subsequent analysis was to assess whether preprocedural anxiety was associated with self-reported and researcher observed pain scores. Anxiety before the dressing change was assessed using an abbreviated State-Trait Anxiety Inventory for Children (range 6-21) and reported with 95% confidence intervals (CI). Self-reported pain was reported using a Visual Analog Scale (range 0-100) and observed pain was assessed using the Face, Legs, Activity, Cry, and Consolability-revised scale. Over half of patients (58.9%) reported mild anxiety (score <12) and about 5% of patients reported severe anxiety (score >16). Younger children (6-8 years) reported higher anxiety scores than older children (15-17 years), but the difference did not achieve statistical significance (mean=12.7, 95% CI: 11.5-13.9, p=0.09). Nonparametric spearman correlation indicated that anxiety score was significantly correlated with observed pain (p=0.01) and self-reported overall pain neared statistical significance (p=0.06). In the final logistic regression of reporting moderate-to-severe pain (pain score >30), the association between anxiety scores and self-reported overall moderate-to-severe pain was statistically significant (p=0.03) when adjusting for race, healing degree, and pain medication use within 6 hours prior to burn dressing care. This pilot study provides preliminary data showing that anxiety before outpatient pediatric burn dressing changes is significantly associated with self-reported overall moderate-to-severe pain.

Physiologic dysregulation in newborns with prenatal opioid exposure: Cardiac, respiratory and movement activity

BACKGROUND

Newborns with prenatal opioid exposure (POE) are commonly diagnosed with neonatal abstinence/opioid-withdrawal syndromes due to characteristic symptoms and overt behaviors. However, little is known about the underlying physiology of opioid-exposed newborns.

OBJECTIVE

Cardiac, respiratory and movement activity were measured to identify physiologic dysregulation and quantify pathophysiologic instabilities of the central and autonomic nervous systems in POE newborns.

METHODS

In this pilot study, 30 hospitalized POE newborns (>35 wks gestational age) participated in one of two study phases wherein physiologic activity was measured for an 8-10 h session. In Phase 1, 17 infants received usual treatment to provide a general assessment of physiologic activity. In Phase 2, 13 infants participated in an interventional study (NCT02768844) using a prototype mattress that delivered stochastic vibratory stimulation (SVS). Changes in physiologic activity were compared for device on (N) and off (F) for three interfeed periods (FNF or NFN).

RESULTS

Phase 1 showed that although infants' heart rate was on average within normal newborn range (mean 137 bpm, SD 7), infants were tachycardic 16% of the study period and tachypneic (mean 74 breaths/min, SD 13) 62% of the period. Infants moved 33% of the period; 17% were durations >30 s. In Phase 2, heart rate, respiratory rate, movement duration and frequency were each reduced for SVS N compared to SVS F in the FNF protocol (P < 0.05).

CONCLUSION

Findings support that physiologic measures can identify dysregulation not captured with current withdrawal scoring assessments. Larger studies are warranted to assess if mattress SVS helps regulate pathophysiologic instabilities in infants with POE.

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.

Prenatal exposure to morphine impairs attention and impulsivity in adult rats

RATIONALE

An alarming number of neonates born with prenatal exposure to morphine has resulted from the opioid epidemic; however, the long-term effects of prenatal opioid exposure on offspring behavior remain relatively unknown. In this study, we evaluated whether prenatal exposure to the mu opioid receptor agonist, morphine, has enduring effects on cognitive functions in adult life.

METHODS

On embryonic days 11-18 (E11-E18), female pregnant rats were injected subcutaneously with either morphine or saline twice daily. Adult male offspring that was prenatally exposed to saline or morphine was trained in the 5-choice serial reaction time test (5-CSRTT) to test their cognitive abilities under baseline conditions. Next, these rats were treated with saline (1 ml/kg), naloxone (1 mg/kg), and acute morphine (1, 3, 5 mg/kg), subcutaneously, once daily and following drug challenges rats were tested in the 5-CSRTT. Meanwhile, behavioral performance on training days between opioid drug challenges were analyzed to monitor possible drug-induced shifts in baseline performance. As a final experiment in order to investigate subchronic exposure to morphine, rats were injected with 5 mg/kg morphine for 5 days and then naloxone in the last day of the experiment (day 6).

RESULTS

Firstly, during acquisition of a stable baseline in the training phase, rats prenatally exposed to morphine showed delayed learning of the task demands. Furthermore, under baseline responding the rats prenatally exposed to morphine showed declined inhibitory control demonstrated by increased impulsive and compulsive-like responding compared to rats prenatally exposed to saline. Moreover, acute and subchronic morphine challenges in the rats prenatally exposed to morphine caused a deficit in visuospatial attention in comparison with saline treatment as well as the rats prenatally exposed to saline. These effects were abolished by naloxone.

CONCLUSION

The current findings indicate a direct causal effect of prenatal morphine exposure on inhibitory control and task learning later in life, as well as deficits in attention following morphine exposure in adulthood.

Maternal morphine intake during pregnancy and lactation affects the circadian clock of rat pups

Early-life morphine exposure causes a variety of behavioural and physiological alterations observed later in life. In the present study, we investigated the effects of prenatal and early postnatal morphine on the maturation of the circadian clockwork in the suprachiasmatic nucleus and the liver, and the rhythm in aralkylamine N-acetyltransferase activity in the pineal gland. Our data suggest that the most affected animals were those born to control, untreated mothers and cross-fostered by morphine-exposed dams. These animals showed the highest mesor and amplitude in the rhythm of Per2, Nr1d1 but not Per1 gene expression in the suprachiasmatic nuclei (SCN) and arrhythmicity in AA-NAT activity in the pineal gland. In a similar pattern to the rhythm of Per2 expression in the SCN, they also expressed Per2 in a higher amplitude rhythm in the liver. Five of seven specific genes in the liver showed significant differences between groups in their expression. A comparison of mean relative mRNA levels suggests that this variability was caused mostly by cross-fostering, animals born to morphine-exposed dams that were cross-fostered by control mothers and vice versa differed from both groups of natural mothers raising offspring. Our data reveal that the circadian system responds to early-life morphine administration with significant changes in clock gene expression profiles both in the SCN and in the liver. The observed differences between the groups suggest that the dose, timing and accompanying stress events such as cross-fostering may play a role in the final magnitude of the physiological challenge that opioids bring to the developing circadian clock.

Pregnancy Status is Associated With Screening for Alcohol and Other Substance Use in the Emergency Department

OBJECTIVES

Determine the rates of screening for substance use in pregnant women versus non-pregnant women attending the emergency department (ED).

METHODS

We captured all ED visits by women of childbearing age (12-50 years in our study) over a 5-year period (2012-2017) (n = 72,752) from a local community hospital. The 2742 pregnant women were then matched by ethnicity, marital status, and arrival method to 9888 non-pregnant women. We then compared rates of screening for substance use by pregnancy status stratifying by age and diagnosis.

RESULTS

The proportion of non-pregnant women who were screened for substance use was 3.66% compared to 1.90% of pregnant women, yielding an odds ratio (OR) of 1.96 (95% CI = 1.44 to 2.67). We then stratified the results by presenting complaint and age. Non-pregnant women 14 to 19 and 30 to 34 had the highest likelihood for screening (OR > 3.0). The presenting complaint showed little effect on screening.

CONCLUSION

Pregnant women were screened only 51% as often as non-pregnant women for substance use in the ED. These results are of particular concern as we continue to see a rise in substance use during pregnancy which results in an increased burden on the healthcare system and society. This study replicates a previous study showing that the rates of screening are lower for pregnant women than non-pregnant women presenting to the ED. Earlier recognition of substance use offers increased opportunities for intervention and prevention of adverse outcomes from substance use during both the current pregnancy and future pregnancies.

Enhanced H3K4 Trimethylation in TNF-α Promoter Gene Locus with Cell Apoptosis in the Ventral-Medial Striatum following Opioid Withdrawal of Neonatal Rat Offspring from Morphine-Addicted Mothers

Prenatal opioid exposure might disturb epigenetic programming in the brain of neonatal offspring with various consequences for gene expressions and behaviors. This study determined whether altered trimethylation of histone 3 at lysine 4 (H3K4me3) in the promoter of the tumor necrosis factor-α (tnf-α) gene with neural cell apoptosis was involved in the ventral-medial striatum, an important brain region for withdrawal symptoms, of neonatal rat offspring from morphine-addicted mothers. Female adult rats were injected with morphine before gestation and until 14 days after giving birth. On postnatal day 14 (P14), rat offspring from morphine-addicted mothers were subjected to an opioid-withdrawal protocol and were analyzed 2 or 8 h after administration of that protocol. Expressions of the TNF-α protein, H3K4me3 in the tnf-α promoter gene, and neural cell apoptosis within the ventral-medial striatum of neonatal rat offspring were evaluated. In the absence of significant opioid withdrawal (2 h after initiation of the opioid-withdrawal protocol on P14), prenatal morphine exposure led to increased levels of H3K4me3 in the tnf-α promoter gene, of the TNF-α protein, and of neural cell apoptosis within the ventral-medial striatum of neonatal rat offspring. Following opioid withdrawal (8 h after initiation of the opioid-withdrawal protocol on P14), differential expression of H3K4me3 in the tnf-α promoter gene locus and upregulation of the level of TNF-α protein expression were further enhanced in these offspring. In addition, increased levels of caspase-3 and neural cell apoptosis were also observed. Taken together, this study revealed that prenatal opioid exposure can activate an epigenetic histone mechanism which regulates proinflammatory factor generation, which hence, led to cell apoptotic damage within the ventral-medial striatum of neonatal rat offspring from morphine-addicted mothers. More importantly, the opioid-withdrawal episode may provide augmented effects for the abovementioned alterations and could lead to deleterious effects in the neonatal brain of such offspring.

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.

Methadone effectively attenuates acute and long-term consequences of neonatal repetitive procedural pain in a rat model

BACKGROUND

Painful procedures in early life cause acute pain and can alter pain processing at a spinal level lasting into adulthood. Current methods of analgesia seem unable to prevent both acute and long-term hypersensitivity associated with neonatal pain. The current study aims to prevent acute and long-term hypersensitivity associated with neonatal procedural pain using methadone analgesia in rat pups.

METHODS

Sprague-Dawley rat pups received either methadone (1 mg/kg) or saline prior to repetitive needle pricks into the left hind paw from the day of birth (postnatal day (P)0) to P7. Control littermates received a tactile stimulus. Mechanical sensitivity was assessed during the neonatal period (P0-P7), from weaning to adulthood (3-7 weeks) and following surgical re-injury of the same dermatome in adulthood.

RESULTS

Methadone administration completely reversed acute hypersensitivity from P0 to P7. In addition, neonatal methadone analgesia prevented prolonged hypersensitivity after re-injury in adulthood, without affecting sensitivity from weaning to adulthood.

CONCLUSIONS

The current study shows that neonatal methadone analgesia can attenuate acute as well as long-term hypersensitivity associated with neonatal procedural pain in a rat model.

IMPACT

Methadone treatment attenuates acute and long-term hypersensitivity associated with neonatal pain in a rat model. Clinical effectiveness studies are urgently warranted to assess acute and long-term analgesic effectivity of methadone.

Maternal Morphine Exposure and Post-Weaning Social Isolation Impair Memory and Ventral Striatum Dopamine System in Male Offspring: Is an Enriched Environment Beneficial?

Maternal opioids abuse has some deleterious consequences on next generations. Besides, children's rearing conditions can affect the behavioral states and brain plasticity in their later life. In the present study, we investigated the effects of maternal morphine (MOR) treatment and post-weaning rearing conditions on memory, pain threshold, and the ventral striatum dopaminergic activity in male offspring. Female Wistar rats were treated twice daily either with escalating doses of MOR or with normal saline (NS) one week before mating, during pregnancy and lactation. After weaning, the male pups were assigned to six groups and then raised for an 8-week period under three different conditions: standard (STD), isolated (ISO) or enriched environment (EE). The behavioral tests, including passive avoidance task, novel object recognition, and tail-flick test, were also performed. Moreover, the ventral striatum dopamine's content (DA), mRNA expressions of dopamine receptor 1(D1R) and dopamine receptor 2 (D2R), and dopamine transporter (DAT) were evaluated. The obtained data showed that maternal MOR exposure and post-weaning social isolation could dramatically impair memory in offspring, while EE could reverse these adverse outcomes. Moreover, results of tail flick latency indicated the increased pain threshold in EE animals. At molecular level, maternal MOR injections and social isolation reduced DA levels and altered expressions of D1R, D2R, and DAT within the ventral striatum of these male offspring. However, post-weaning EE partially buffered these changes. Our finding signified the effects of maternal MOR exposure and social isolation on the behaviors and neurochemistry of brain in next generation, and it also provided evidence on reversibility of these alterations following EE.

Identifying the Neurodevelopmental Differences of Opioid Withdrawal

Stopping opioid medications can result in a debilitating withdrawal syndrome in chronic users. Opioid withdrawal can occur at all ages, but mechanistic understanding of this condition is predominantly derived from adult studies. Here, we examined whether there are age-dependent differences in the behavioural phenotype and cellular indices of opioid withdrawal. We tested this by assessing the behavioural and cFos response (a surrogate marker for neuronal activation) to morphine withdrawal in C57BL/6J mice across key developmental stages-neonatal, adolescent, and adulthood. Mice in all age groups received escalating doses of morphine (10-50 mg/kg) over 5 days and withdrawal was precipitated by a single injection of the opioid receptor antagonist naloxone (2 mg/kg) two hours after the last morphine dose. In adult and adolescent mice, withdrawal behaviours were robust, with age-related differences in autonomic and somatic signs. In both groups, cFos expression was increased in spinally projecting neurons within the Periaqueductal Grey (PAG), Rostro-ventromedial Medulla (RVM), and Locus Coeruleus. Neonatal animals displayed both a distinct behavioural withdrawal and cFos expression profile. Notably, in young animals cFos expression was increased within the PAG and LC, but decreased in the RVM. In summary, naloxone challenge precipitated robust opioid withdrawal behaviours across all developmental stages with neonatal animals displaying differences in withdrawal behaviours and unique neuronal activation patterns within key brainstem regions.

Evaluation of μ-Opioid System Functionality in Mouse Pups: Ultrasonic Vocalizations as an Index of Infant Attachment

The evaluation of ultrasonic vocalizations (USVs) during isolation in 6-8-day-old mouse pups can give an indication of the perception of pups' discomfort and need for caretaker presence to overcome the unpleasant condition. Time spent vocalizing changed according to opioid activation, stress exposure, and genetic profile of pups. Deficits in attachment suggest altered opioid functioning and predisposal for long-term defective social behaviors and reward processes.

Stories of Loss: Separation of Children and Mothers Who Use Opioids

In the present article, we examine the experiences of women who use opioids and have lost children to governing agencies or family members with a focus on access to resources. We conducted 28 qualitative interviews with mothers who misused opioids and lost custody of their children. Their narratives are analyzed within a social capital framework. Mothers with both negative and positive social capital, whose children were removed, desired to regain their maternal role. However, mothers with negative social capital had increased difficulty navigating the judicial system and accessing needed services, were less likely to remain in treatment, more likely to use drugs, and less likely to regain custody of their children than women with positive social capital. We suggest that medical, social, and law enforcement agencies do more to link mothers who misuse opioids with positive social capital in order to increase their participation and retention in treatment and help keep families intact.