Effects of perinatal buprenorphine and methadone exposures on striatal cholinergic ontogeny

Neurobehavioral Characterization of Perinatal Oxycodone-Exposed Offspring in Early Adolescence

The opioid epidemic has received considerable attention, but the impact on perinatal opioid-exposed (POE) offspring remains underexplored. This study addresses the emerging public health challenge of understanding and treating POE children. We examined two scenarios using preclinical models: offspring exposed to oxycodone (OXY) in utero (IUO) and acute postnatal OXY (PNO). We hypothesized exposure to OXY during pregnancy primes offspring for neurodevelopmental deficits and severity of deficits is dependent on timing of exposure. Notable findings include reduced head size and brain weight in offspring. Molecular analyses revealed significantly lower levels of inflammasome-specific genes in the prefrontal cortex (PFC). Gene Set Enrichment Analysis (GSEA) and Ingenuity Pathway Analysis (IPA) highlighted the enrichment of genes associated with mitochondrial and synapse dysfunction in POE offspring. Western blot analysis validated IPA predictions of mitochondrial dysfunction in PFC-derived synaptosomes. Behavioral studies identified significant social deficits in POE offspring. This study presents the first comparative analysis of acute PNO- and IUO-offspring during early adolescence finding acute PNO-offspring have considerably greater deficits. The striking difference in deficit severity in acute PNO-offspring suggests that exposure to opioids in late pregnancy pose the greatest risk for offspring well-being.

Developmental outcomes with perinatal exposure (DOPE) to prescription opioids

Researchers have found considerable evidence in the past 20 years that perinatal opioid exposure leads to an increased risk of developmental disorders in offspring that persist into adulthood. The use of opioids to treat pain concerning pregnancy, delivery, and postpartum complications has been rising. As a result, communities have reported a 300-400 % increase in Neonatal Opioid Withdrawal Syndrome (NOWS). NOWS represents the initial stage of several behavioral, phenotypic, and synaptic deficits. This review article summarizes the Developmental Outcomes of Perinatal Exposure (DOPE) to prescription opioids. Moreover, we also seek to connect these findings to clinical research that describes DOPE at multiple stages of life. Since specific mechanisms that underlie DOPE remain unclear, this article aims to provide a framework for conceptualizing across all ages and highlight the implications they may have for longevity.

Chronic exposure to methadone induces activated microglia and astrocyte and cell death in the cerebellum of adult male rats

Methadone is a centrally-acting synthetic opioid analgesic widely used in the methadone maintenance therapy (MMT) programs throughout the world. Considering its neurotoxic effects particularly on the cerebellum, this study aims to address the behavioral and histological alterations in the cerebellar cortex associated with methadone administration. Twenty-four adult male albino rats were randomized into two groups of control and methadone treatment. Methadone was subcutaneously administered (2.5-10 mg/kg) once a day for two consecutive weeks. The functional and structural changes in the cerebellum were compared to the control group. Our data revealed that treating rats with methadone not only induced cerebellar atrophy, but also prompted the actuation of microgliosis, astrogliosis, and apoptotic biomarkers. We further demonstrated that treating rats with methadone increased complexity of astrocyte processes and decreased complexity of microglia processes. Our result showed that methadone impaired motor coordination and locomotor performance and neuromuscular activity. Additionally, relative gene expression of TNF-α, caspase-3 and RIPK3 increased significantly due to methadone. Our findings suggest that methadone administration has a neurodegenerative effect on the cerebellar cortex via dysregulation of microgliosis, astrogliosis, apoptosis, and neuro-inflammation.

Prenatal Drugs and Their Effects on the Developing Brain: Insights From Three-Dimensional Human Organoids

Decades of research have unequivocally demonstrated that fetal exposure to both recreational and prescription drugs in utero negatively impacts the developing brain. More recently, the application of cutting-edge techniques in neurodevelopmental research has attempted to identify how the fetal brain responds to specific environmental stimuli. Meanwhile, human fetal brain studies still encounter ethical considerations and technical limitations in tissue collection. Human-induced pluripotent stem cell (iPSC)-derived brain organoid technology has emerged as a powerful alternative to examine fetal neurobiology. In fact, human 3D organoid tissues recapitulate cerebral development during the first trimester of pregnancy. In this review, we aim to provide a comprehensive summary of fetal brain metabolic studies related to drug abuse in animal and human models. Additionally, we will discuss the current challenges and prospects of using brain organoids for large-scale metabolomics. Incorporating cutting-edge techniques in human brain organoids may lead to uncovering novel molecular and cellular mechanisms of neurodevelopment, direct novel therapeutic approaches, and raise new exciting questions.

Consequences of Parental Opioid Exposure on Neurophysiology, Behavior, and Health in the Next Generations

Substance abuse and the ongoing opioid epidemic represents a large societal burden. This review will consider the long-term impact of opioid exposure on future generations. Prenatal, perinatal, and preconception exposure are reviewed with discussion of both maternal and paternal influences. Opioid exposure can have long-lasting effects on reproductive function, gametogenesis, and germline epigenetic programming, which can influence embryogenesis and alter the developmental trajectory of progeny. The potential mechanisms by which preconception maternal and paternal opioid exposure produce deleterious consequences on the health, behavior, and physiology of offspring that have been identified by clinical and animal studies will be discussed. The timing, nature, dosing, and duration of prenatal opioid exposure combined with other important environmental considerations influence the extent to which these manipulations affect parents and their progeny. Epigenetic inheritance refers to the transmission of environmental insults across generations via mechanisms independent of the DNA sequence. This topic will be further explored in the context of prenatal, perinatal, and preconception opioid exposure for both the maternal and paternal lineage.

Prenatal exposure to methadone or buprenorphine alters µ-opioid receptor binding and downstream signaling in the rat brain

There is a growing concern related to the use of opioid maintenance treatment during pregnancy. Studies in both humans and animals have reported reduced cognitive functioning in offspring prenatally exposed to methadone or buprenorphine; however, little is known about the neurobiological mechanisms underlying these impairments. To reveal possible neurobiological effects of such in utero exposure, we examined brain tissue from methadone- and buprenorphine-exposed rat offspring previously shown to display impaired learning and memory. We studied µ-opioid receptor (MOR) and N-methyl-D-aspartate receptor (NMDAR) binding in the rat offspring cerebrum during development and in the hippocampus at young adulthood. Moreover, we examined activation of the Ca2+ /calmodulin-dependent protein kinase II (CaMKII) and the extracellular signal-regulated kinase (ERK), which are central in the downstream signaling of these receptors. The methadone- and buprenorphine-exposed rat pups displayed reduced MOR binding up to two weeks after birth, whereas the NMDAR binding was unaffected. Prenatal exposure to methadone or buprenorphine also resulted in decreased activation of CaMKII and/or ERK during development, while young adult offspring displayed increased hippocampal ERK activation. In conclusion, our findings suggest that prenatal exposure to exogenous opioids, such as methadone or buprenorphine, may disturb the endogenous opioid system during development, with long-term effects on proteins important for cognitive functioning.

N-acetylcysteine mitigates acute opioid withdrawal behaviors and CNS oxidative stress in neonatal rats

BACKGROUND

Neonatal abstinence syndrome (NAS) is a significant problem. Opioid withdrawal induces oxidative stress and disrupts glutamate and glutathione homeostasis. We hypothesized that N-acetylcysteine (NAC) administered during acute opioid withdrawal in neonatal rats would decrease withdrawal behaviors and normalize CNS glutathione and glutamate.

METHODS

Osmotic minipumps with methadone (opioid dependent, OD) and saline (Sham) were implanted into Sprague Dawley dams 7 days prior to delivery. Pups were randomized to receive either naloxone plus saline or NAC (50-100 mg/kg), administered on postnatal day (PND) 7. We performed MR spectroscopy on PND6-7 before, 30 min, and 120 min after withdrawal. On PND7, we assessed withdrawal behaviors for 90 min after naloxone administration and summed scores during peak withdrawal period.

RESULTS

Mean summed behavioral scores were significantly different between groups (χ² (2) = 10.49, p = 0.005) but not different between NAC/NAL/OD and Sham (p = 0.14): SAL/NAL/OD = 17.2 ± 4.2 (n = 10); NAC/NAL/OD = 11.3 ± 5.6 (n = 9); Sham = 6.5 ± 0.6 (n = 4). SAL/NAL/OD pups had decreased glutathione at 120 min (p = 0.01), while NAC/NAL/OD pups maintained pre-withdrawal glutathione (p = 0.26).

CONCLUSION

In antenatal OD, NAC maintains CNS glutathione and mitigates acute opioid withdrawal in neonatal rats. This is the first study to demonstrate acute opioid withdrawal neurochemical changes in vivo in neonatal OD. NAC is a potential novel treatment for NAS.

Opioids affect the fetal brain: reframing the detoxification debate

Medication-assisted treatment is recommended for individuals with an opioid use disorder, including pregnant women. Medication-assisted treatment during pregnancy provides benefits to the mother and fetus, including better pregnancy outcomes, reduced illicit drug use, and improved prenatal care. An alternative approach, medically supervised withdrawal (detoxification), has, in recent reports, demonstrated a low risk of fetal death and low rates of relapse and neonatal abstinence syndrome. The rates of relapse and neonatal abstinence syndrome are questioned by many who view medically supervised withdrawal as unacceptable based on the concern for the potential adverse consequences of relapse to mother and baby. The impact of opioids on the fetal brain have not been integrated into this debate. Studies in animals and human brain tissues demonstrate opioid receptors in neurons, astroglia, and oligodendrocytes. Age-specific normative data from infants, children, and adults have facilitated investigation of the impact of opioids on the human brain in vivo. Collectively, these studies in animals, human neural tissue, adult brains, and the brains of children and newborns demonstrate that opioids adversely affect the human brain, primarily the developing oligodendrocyte and the processes of myelinization (white matter microstructure), connectivity between parts of the brain, and the size of multiple brain regions, including the basal ganglia, thalamus, and cerebellar white matter. These in vivo studies across the human lifespan suggest vulnerability of specific fronto-temporal-limbic and frontal-subcortical (basal ganglia and cerebellum) pathways that are also likely vulnerable in the human fetal brain. The long-term impact of these reproducible changes in the fetal brain in vivo is unclear, but the possibility of lasting injury has been suggested. In light of the recent data on medically supervised withdrawal and the emerging evidence suggesting adverse effects of opioids on the developing fetal brain, a new paradigm of care is needed that includes the preferred option of medication-assisted treatment but also the option of medically supervised opioid withdrawal for a select group of women. Both these treatment options should offer mental health and social services support throughout pregnancy. More research on both opioid exposure on the developing human brain and the impact of medically supervised withdrawal is required to identify appropriate candidates, optimal dose reduction regimens, and gestational age timing for initiating medically supervised withdrawal.

Gestational buprenorphine exposure: Effects on pregnancy, development, neonatal opioid withdrawal syndrome, and behavior in a translational rodent model

BACKGROUND

The opioid crisis has led to an increased number of pregnant opioid-dependent women receiving opioid-maintenance therapy (e.g. buprenorphine, BUP), but little is known about the consequences of gestational BUP exposure on pregnancy outcomes, maternal care, or offspring development.

METHODS

Our translational rodent model began BUP exposure to adult female rats (N = 30) at least 7 days before conception and continued throughout the postpartum period. Both therapeutic low-dose (BUP-LD, 0.3 mg/kg, s.c.) and overexposure high-dose (BUP-HD, 1.0 mg/kg) doses of BUP were compared to saline control. Female rats were bred in house with drug-naïve adult male rats. The day after parturition, litters were culled to 5 males/5 females and assigned randomly to various behavioral tests and assessed either neonates or adolescents. Litter characteristics, maternal caregiving, Neonatal Opioid Withdrawal Syndrome (NOWS), offspring development and adolescent behaviors were evaluated.

RESULTS

BUP-LD decreased maternal care, delayed offspring development, decreased offspring body weight, length, temperature, and pain sensitivity (p's < .05). BUP-HD drastically reduced maternal care and offspring survival, altered litter characteristics, and increased NOWS (p's < .05).

CONCLUSION

These results demonstrate that the therapeutic BUP-LD in rats was relatively safe with subtle effects on maternal care and rodent offspring. However, overexposure BUP-HD in rats produced NOWS and compromised maternal caregiving as well as rodent offspring survival. More research is critical to validate the translational implication of these findings for human opioid-dependent mothers maintained on BUP-maintenance therapy.

Visual and oculomotor outcomes in children with prenatal opioid exposure

PURPOSE OF REVIEW

To summarize the visual and oculomotor outcomes in children with prenatal opioid exposure and review the effects of opioids on the developing central nervous system.

RECENT FINDINGS

Animal models and imaging studies in children suggest that prenatal opioid exposure may affect neuronal survival and result in delayed maturation of white matter tracts and decreased volumes in certain brain areas. Visual evoked potential testing in children demonstrates delayed maturation of the afferent visual system in opioid-exposed groups compared with controls, though 'catch-up' development is seen with longitudinal follow-up. Strabismus and nystagmus are also more common in exposed children, and these findings appear to persist.

SUMMARY

As rates of opioid dependence and prenatal opioid exposure continue to increase, it is important to evaluate the short-term and long-term effects of opioids on the developing visual system. An understanding of these risks is important when counseling the parents or guardians of opioid-exposed children, though larger studies with more long-term follow-up will improve our prognostic abilities.

Modeling prenatal opioid exposure in animals: Current findings and future directions

The past decade has seen a drastic rise in the number of infants exposed to opioids in utero. It is unclear what lasting effect this exposure may have on these children. Animal models of prenatal opioid exposure may provide insight into potential areas of vulnerability. The present review summarizes the findings across animal models of prenatal opioid exposure, including exposure to morphine, methadone, buprenorphine, and oxycodone. Details regarding the drug, doses, and duration of treatment, as well as key findings, are summarized in tables with associated references. Finally, significant gaps in the current preclinical literature and future directions are discussed.

Fetal assessment in buprenorphine-maintained women using fetal magnetoencephalography: a pilot study

BACKGROUND AND AIMS

In-utero exposure to opioids including buprenorphine (BUP) has been shown to affect fetal activity, specifically heart-rate variability (FHRV) and fetal movement (FM). Our objective was to extract simultaneous recordings of fetal cardiac and brain-related activity in BUP-maintained and non-opioid exposed pregnant women using a novel non-invasive biomagnetic technique.

DESIGN

A pilot study was conducted, recording and analyzing biomagnetic data from fetuses of BUP-maintained and non-opioid exposed pregnant women. Signals were acquired with the non-invasive 151-channel SARA (SQUID-Array for Reproductive Assessment) system. Advanced signal-processing techniques were applied to extract fetal heart and brain activity.

SETTING

University of Arkansas for Medical Sciences (UAMS, Little Rock, Arkansas, USA).

PARTICIPANTS

Eight BUP-maintained pregnant women from UAMS Women's Mental Health Program between gestational ages (GA) of 29-37 weeks who were treated with 8-24 mg of BUP daily. Sixteen pregnant women with no known opioid exposure in the same GA range were also included.

MEASUREMENTS

Outcome measures from the fetal heart and brain signals included: heart rate (FHR), FM, FHR accelerations, FHR-FM coupling, FHRV, fetal behavioral states (FBS) and power spectral density (PSD) of spontaneous brain activity. These measures were analyzed at three GA intervals.

FINDINGS

Fetal heart and brain activity parameters were extracted and quantified successfully from 18 non-opioid and 16 BUP recordings. Overall analysis in both groups show that: FHR and FM ranged from 131 to 141 beats per minute (b.p.m.) and 5 to 11 counts, respectively. In the 35-37 weeks GA, the coupling duration (~9 s) was the shortest, while three of the FHRV parameters were the highest. The PSD of brain activity revealed highest power in 0.5-4 Hz bandwidth. Transitions in FBS from quiet to active sleep were > 50% of sessions.

CONCLUSIONS

This pilot study showed that a novel biomagnetic technique allows simultaneous quantification of cardiac and brain activities of a group of buprenorphine-exposed and non-exposed fetuses in the third trimester.

Neuroanatomical characteristics of youths with prenatal opioid and poly-drug exposure

Neuroanatomical and cognitive differences have been documented during childhood between children with prenatal opioid- and poly-drug exposure and controls in small samples. We investigated whether these differences persisted in larger samples of youth at older ages. Quantitative MRI and cognitive data were compared between 38 youths in the risk group and 44 youths in the non-exposed group (aged 17 to 22 years) who had been followed prospectively since birth. Most drug-exposed youths (84%) moved to permanent foster or adoptive homes before one year of age. The drug-exposed group displayed smaller neuroanatomical volumes (0.70 SD difference in total brain volume, p = 0.001), smaller cortical surface areas and thinner cortices than the comparison group. The birth weight accounted for some of the intergroup differences. Neuroanatomical characteristics partially mediated group differences in cognitive function. The present study cannot differentiate between causal factors but indicates persistent neurocognitive differences associated with prenatal opioid or poly-drug exposure.

Expression of kappa opioid receptors in developing rat brain - Implications for perinatal buprenorphine exposure

Buprenorphine, a mu opioid receptor partial agonist and kappa opioid receptor (KOR) antagonist, is an emerging therapeutic agent for maternal opioid dependence in pregnancy and neonatal abstinence syndrome. However, the endogenous opioid system plays a critical role in modulating neurodevelopment and perinatal buprenorphine exposure may detrimentally influence this. To identify aspects of neurodevelopment vulnerable to perinatal buprenorphine exposure, we defined KOR protein expression and its cellular associations in normal rat brain from embryonic day 16 to postnatal day 23 with double-labelling immunohistochemistry. KOR was expressed on neural stem and progenitor cells (NSPCs), choroid plexus epithelium, subpopulations of cortical neurones and oligodendrocytes, and NSPCs and subpopulations of neurones in postnatal hippocampus. These distinct patterns of KOR expression suggest several pathways vulnerable to perinatal buprenorphine exposure, including proliferation, neurogenesis and neurotransmission. We thus suggest the cautious use of buprenorphine in both mothers and infants until its impact on neurodevelopment is better defined.

Prenatal buprenorphine exposure and neonatal neurobehavioral functioning

AIMS

Assessments of effects of prenatal opioid exposure on the neonate have consisted principally of evaluations of neonatal abstinence syndrome (NAS) to determine the need for pharmacotherapy. The purpose of this study was to comprehensively evaluate the effects of gestational maternal buprenorphine maintenance on newborn neurobehavioral functioning.

STUDY DESIGN

Maternal substance use history and psychosocial demographics that can contribute to the neurobehavioral functioning of the infant were explored. Infants were assessed using the NICU Network Neurobehavioral Scale (NNNS) to measure their neurologic and behavioral functioning and signs of stress/abstinence on days 3, 14 and 30 of life.

SUBJECTS

Participants were 41 pregnant buprenorphine-maintained women and their infants.

RESULTS

Maternal buprenorphine dose at delivery was negatively correlated with infant quality of movement and self-regulation, and positively correlated with the central nervous system parameters of stress/abstinence at day 3 of life. As maternal buprenorphine dose increased, the mean morphine dose that the infant required for NAS treatment significantly increased. No differences were found when comparing the NNNS domain scores between infants who required pharmacotherapy for NAS versus those who did not at day 3 of life.

CONCLUSIONS

Buprenorphine exposure during pregnancy can alter neonatal neurobehavioral and physiological responses to stimuli. A systematic evaluation of the newborn's functional domains above NAS assessment alone is crucial to address the challenges created by neurobehavioral dysregulation associated with substance exposure, improve caregiver/infant interaction and developmental trajectory. Comprehensive pre/postnatal treatment of buprenorphine-maintained mothers can lead to healthier outcomes for the dyad.

Early inhibitory control and working memory abilities of children prenatally exposed to methadone

BACKGROUND

Methadone maintenance is the most common method of treating opioid-dependent pregnant women. However, little is known about the impact of prenatal methadone exposure on child neurocognitive development.

AIMS

To examine the early executive functioning of children born to methadone-maintained mothers, and to assess relations between executive functioning and later emotional and behavioral adjustment.

STUDY DESIGN

Prospective longitudinal study.

PARTICIPANTS

The sample consisted of 68 methadone-exposed children and 88 non-methadone-exposed children.

OUTCOME MEASURES

At age 2years, children's inhibitory control and working memory were assessed using the Snack Delay and Three Boxes tasks. At 2 and 4.5years, their emotional and behavioral adjustment was assessed using the caregiver-completed Strengths and Difficulties Questionnaire.

RESULTS

Methadone-exposed children had poorer inhibitory control than non-exposed children (p<0.0001). These differences were explained by maternal education and prenatal benzodiazepine use. With respect to working memory, although both groups performed similarly on the first trial set, non-exposed children significantly improved their performance on the second trial set (p=0.002), while methadone-exposed children did not (p=0.92). Inhibitory control at age 2years was predictive of higher conduct (p=0.001), hyperactivity (p=0.0001), peer relationship (p=0.02), and total (p<0.0001) problems at 4.5years even after adjustment for behavioral problems at 2years.

CONCLUSIONS

Methadone-exposed children demonstrate difficulties with inhibitory control and possibly sustained attention/learning. These difficulties were explained by factors correlated with maternal prenatal methadone use. Longer-term follow-up of these children is needed to understand the effects of prenatal methadone exposure and related maternal factors on executive functioning and behavioral adjustment.

Evaluating the control: minipump implantation and breathing behavior in the neonatal rat

We evaluated genioglossus (GG) gross motoneuron morphology, electromyographic (EMG) activities, and respiratory patterning in rat pups allowed to develop without interference (unexposed) and pups born to dams subjected to osmotic minipump implantation in utero (saline-exposed). In experiment 1, 48 Sprague-Dawley rat pups (Charles-River Laboratories), ages postnatal day 7 (P7) through postnatal day 10 (P10), were drawn from two experimental groups, saline-exposed (n = 24) and unexposed (n = 24), and studied on P7, P8, P9, or P10. Pups in both groups were sedated (Inactin hydrate, 70 mg/kg), and fine-wire electrodes were inserted into the GG muscle of the tongue and intercostal muscles to record EMG activities during breathing in air and at three levels of normoxic hypercapnia [inspired CO2 fraction (FiCO2 ): 0.03, 0.06, and 0.09]. Using this approach, we assessed breathing frequency, heart rate, apnea type, respiratory event types, and respiratory stability. In experiment 2, 16 rat pups were drawn from the same experimental groups, saline-exposed (n = 9) and unexposed (n = 7), and used in motoneuron-labeling studies. In these pups a retrograde dye was injected into the GG muscle, and the brain stems were subsequently harvested and sliced. Labeled GG motoneurons were identified with microscopy, impaled, and filled with Lucifer yellow. Double-labeled motoneurons were reconstructed, and the number of primary projections and soma volumes were calculated. Whereas pups in each group exhibited the same number (P = 0.226) and duration (P = 0.093) of respiratory event types and comparable motoneuron morphologies, pups in the implant group exhibited more central apneas and respiratory instability relative to pups allowed to develop without interference.

Consequences of prenatal opioid use for newborns

One-third of childbearing women take prescription opioids, previously occurring only in 6-7% of pregnant women. Prenatal opioid exposures may cause birth defects, altered brain development and neonatal abstinence syndrome (NAS). NAS incidence increased fourfold and length of stay increased from 13 to 19 days over 10 years (2004-2013), leading to sevenfold increases in NICU days due to NAS. Initial data suggest that recent NAS increases have resulted from increased use of prescription opioids rather than illicit drugs.

CONCLUSION

Paediatricians will have to manage the consequences of prenatal opioid exposures, as the offspring often have complex medical and social issues associated with these families.

Developmental consequences of fetal exposure to drugs: what we know and what we still must learn

Most drugs of abuse easily cross the placenta and can affect fetal brain development. In utero exposures to drugs thus can have long-lasting implications for brain structure and function. These effects on the developing nervous system, before homeostatic regulatory mechanisms are properly calibrated, often differ from their effects on mature systems. In this review, we describe current knowledge on how alcohol, nicotine, cocaine, amphetamine, Ecstasy, and opiates (among other drugs) produce alterations in neurodevelopmental trajectory. We focus both on animal models and available clinical and imaging data from cross-sectional and longitudinal human studies. Early studies of fetal exposures focused on classic teratological methods that are insufficient for revealing more subtle effects that are nevertheless very behaviorally relevant. Modern mechanistic approaches have informed us greatly as to how to potentially ameliorate the induced deficits in brain formation and function, but conclude that better delineation of sensitive periods, dose-response relationships, and long-term longitudinal studies assessing future risk of offspring to exhibit learning disabilities, mental health disorders, and limited neural adaptations are crucial to limit the societal impact of these exposures.

Visual selective attention is impaired in children prenatally exposed to opioid agonist medication

AIMS

To examine whether prenatal exposure to opioid agonist medication is associated with visual selective attention and general attention problems in early childhood.

METHOD

Twenty-two children (mean age = 52.17 months, SD = 1.81) prenatally exposed to methadone, 9 children (mean age = 52.41 months, SD = 1.42) prenatally exposed to buprenorphine and 25 nonexposed comparison children (mean age = 51.44 months, SD = 1.31) were tested. Visual selective attention was measured with a Tobii 1750 Eye Tracker using a spatial negative priming paradigm. Attention problems were measured using the Child Behavior Checklist.

RESULTS

The comparison group demonstrated a larger spatial negative priming effect (mean = 23.50, SD = 45.50) than the exposed group [mean = -6.84, SD = 86.39, F(1,50) = 5.91, p = 0.019, η(2) = 0.11]. No difference in reported attention problems was found [F(1,51) = 1.63, p = 0.21, η(2) = 0.03]. Neonatal abstinence syndrome and prenatal exposure to marijuana were found to predict slower saccade latencies in the exposed group (b = 54.55, SE = 23.56, p = 0.03 and b = 88.86, SE = 32.07, p = 0.01, respectively).

CONCLUSION

Although exposed children did not appear to have attention deficits in daily life, lower performance on the SNP task indicates subtle alteration in the attention system.

The opioid system and brain development: effects of methadone on the oligodendrocyte lineage and the early stages of myelination

Oligodendrocytes express opioid receptors throughout development, but the role of the opioid system in myelination remains poorly understood. This is a significant problem as opioid use and abuse continue to increase in two particular populations: pregnant addicts (in whom drug effects could target early myelination in the fetus and newborn) and adolescents and young adults (in whom late myelination of 'higher-order' regions takes place). Maintenance treatments for opioid addicts include the long-lasting opioids methadone and buprenorphine. Similar to our previous findings on the effects of buprenorphine, we have now found that early myelination in the developing rat brain is also altered by perinatal exposure to therapeutic doses of methadone. Pups exposed to this drug exhibited elevated brain levels of the 4 major splicing variants of myelin basic protein, myelin proteolipid protein, and myelin-oligodendrocyte glycoprotein. Consistent with the enrichment and function of these proteins in mature myelin, analysis of the corpus callosum in these young animals also indicated an elevated number of axons with already highly compacted myelin sheaths. Moreover, studies in cultured cells showed that methadone exerts direct effects at specific stages of the oligodendrocyte lineage, stimulating the proliferation of progenitor cells while on the other hand accelerating the maturation of the more differentiated but still immature preoligodendrocytes. While the long-term effects of these observations remain unknown, accelerated or increased oligodendrocyte maturation and myelination could both disrupt the complex sequence of synchronized events leading to normal connectivity in the developing brain. Together with our previous observations on the effects of buprenorphine, the present findings further underscore a crucial function of the endogenous opioid system in the control of oligodendrocyte development and the timing of myelination. Interference with these regulatory systems by opioid use or maintenance treatments could disrupt the normal process of brain maturation at critical stages of myelin formation.

Depression-like effect of prenatal buprenorphine exposure in rats

Studies indicate that perinatal opioid exposure produces a variety of short- and long-term neurobehavioral consequences. However, the precise modes of action are incompletely understood. Buprenorphine, a mixed agonist/antagonist at the opioid receptors, is currently being used in clinical trials for managing pregnant opioid addicts. This study provides evidence of depression-like consequence following prenatal exposure to supra-therapeutic dose of buprenorphine and sheds light on potential mechanisms of action in a rat model involving administration of intraperitoneal injection to pregnant Sprague-Dawley rats starting from gestation day 7 and lasting for 14 days. Results showed that pups at postnatal day 21 but not the dams had worse parameters of depression-like neurobehaviors using a forced swimming test and tail suspension test, independent of gender. Neurobehavioral changes were accompanied by elevation of oxidative stress, reduction of plasma levels of brain-derived neurotrophic factor (BDNF) and serotonin, and attenuation of tropomyosin-related kinase receptor type B (TrkB) phosphorylation, extracellular signal-regulated kinase (ERK) phosphorylation, protein kinase A activity, cAMP response element-binding protein (CREB) phosphorylation, and CREB DNA-binding activity. Since BDNF/serotonin and CREB signaling could orchestrate a positive feedback loop, our findings suggest that the induction of oxidative stress, reduction of BDNF and serotonin expression, and attenuation of CREB signaling induced by prenatal exposure to supra-therapeutic dose of buprenorphine provide evidence of potential mechanism for the development of depression-like neurobehavior.

Prenatal buprenorphine exposure decreases neurogenesis in rats

Perinatal opioid exposure has a negative effect on neurogenesis and produces neurological consequences. However, its mechanisms of action are incompletely understood. Buprenorphine, a mixed opioid agonist/antagonist, is an alternative medication for managing pregnant opioid addicts. This study provides evidence of decreased neurogenesis and depression-like consequences following prenatal exposure to buprenorphine and sheds light on mechanisms of action in a rat model involving administration of intraperitoneal injection to pregnant rats starting from gestation day 7 and lasting for 14 days and a cultured neurosphere model. Results of forced swimming test and tail suspension test showed that pups at postnatal day 21 had worse parameters of depression-like neurobehaviors, independent of gender. Neurobehavioral changes were accompanied by reduction of neuronal composition, biochemical parameters of neural stem/progenitor cells, brain-derived neurotrophic factor (BDNF) expression, tropomyosin-related kinase receptor type B phosphorylation, protein kinase A (PKA) activity, and cAMP response element-binding protein phosphorylation. Results of parallel cell studies further demonstrated a negative impact of buprenorphine on cultured neurospheres, including proliferation, differentiation, BDNF expression and signaling, and PKA activity. Taken together, our results suggest that prenatal exposure to buprenorphine might result in depression-like phenotypes associated with impaired BDNF action and decreased neurogenesis in the developing brain of weanlings.

Effect of prenatal methadone on reinstated behavioral sensitization induced by methamphetamine in adolescent rats

It has been known that methadone maintenance treatment is the standard treatment of choice for pregnant opiate addicts. However, there are few data on newborn outcomes especially in the cross talk with other addictive agents. The present study was to investigate the effect of prenatal exposure to methadone on methamphetamine (METH)-induced behavioral sensitization as an indicator of drug addiction in later life. Pregnant rats received saline or methadone (7 mg/kg, s.c.) twice daily from E3 to E20. To induce behavioral sensitization, offspring (5 weeks old) were treated with METH (1mg/kg, i.p.) or saline once daily for 5 consecutive days. Ninety-six hours (day 9) after the 5th treatment with METH or saline, animals received a single dose of METH (1mg/kg, i.p.) or saline to induce the reinstated behavioral sensitization. Prenatal methadone treatment enhanced the level of development of locomotor behavioral sensitization to METH administration in adolescent rats. Prenatal methadone treatment also enhanced the reinstated locomotor behavioral sensitization in adolescent rats after the administration had ceased for 96 h. These results indicate that prenatal methadone exposure produces a persistent lesion in the dopaminergic system, as indicated by enhanced METH-induced locomotor behavioral sensitization (before drug abstinence) and reinstated locomotor behavioral sensitization (after short term drug abstinence) in adolescent rats. These findings show that prenatal methadone exposure may enhance susceptibility to the development of drug addiction in later life. This could provide a reference for drug usage such as methamphetamine in their offspring of pregnant woman who are treating with methadone.

Safety and efficacy of buprenorphine for analgesia in laboratory mice and rats

Buprenorphine is a long-acting opiate with a high therapeutic index. The authors review the pharmacology, toxicity, analgesic effects and delivery of buprenorphine for use in laboratory mice and rats. Buprenorphine-based analgesic therapy has a substantial record of safety, and there is growing evidence of its effectiveness for treating post-operative pain. Nonetheless, more research is needed to determine optimal delivery systems and analgesic regimens for pain therapy in laboratory animals.

Oligodendrocyte responses to buprenorphine uncover novel and opposing roles of μ-opioid- and nociceptin/orphanin FQ receptors in cell development: implications for drug addiction treatment during pregnancy

Although the classical function of myelin is the facilitation of saltatory conduction, this membrane and the oligodendrocytes, the cells that make myelin in the central nervous system (CNS), are now recognized as important regulators of plasticity and remodeling in the developing brain. As such, oligodendrocyte maturation and myelination are among the most vulnerable processes along CNS development. We have shown previously that rat brain myelination is significantly altered by buprenorphine, an opioid analogue currently used in clinical trials for managing pregnant opioid addicts. Perinatal exposure to low levels of this drug induced accelerated and increased expression of myelin basic proteins (MBPs), cellular and myelin components that are markers of mature oligodendrocytes. In contrast, supra-therapeutic drug doses delayed MBP brain expression and resulted in a decreased number of myelinated axons. We have now found that this biphasic-dose response to buprenorphine can be attributed to the participation of both the μ-opioid receptor (MOR) and the nociceptin/orphanin FQ receptor (NOP receptor) in the oligodendrocytes. This is particularly intriguing because the NOP receptor/nociceptin system has been primarily linked to behavior and pain regulation, but a role in CNS development or myelination has not been described before. Our findings suggest that balance between signaling mediated by (a) MOR activation and (b) a novel, yet unidentified pathway that includes the NOP receptor, plays a crucial role in the timing of oligodendrocyte maturation and myelin synthesis. Moreover, exposure to opioids could disrupt the normal interplay between these two systems altering the developmental pattern of brain myelination.

Prenatal exposure to methadone and buprenorphine: a review of the potential effects on cognitive development

The amount of opioid users receiving opioid maintenance therapy has increased significantly over the last few years. As a result, an increasing number of children are prenatally exposed to long-lasting opioids such as methadone and buprenorphine. This article reviews the literature on the cognitive development of children born to mothers in opioid maintenance therapy. Topics discussed are the effects of prenatal exposure on prematurity, somatic growth, brain volume, myelination, and the endocrine and neurotransmitter system. Social-environmental factors, including parental functioning, as well as genetic factors are also described. Areas requiring further research are identified.

Opioid addiction and pregnancy: perinatal exposure to buprenorphine affects myelination in the developing brain

Buprenorphine is a mu-opioid receptor partial agonist and kappa-opioid receptor antagonist currently on trials for the management of pregnant opioid-dependent addicts. However, little is known about the effects of buprenorphine on brain development. Oligodendrocytes express opioid receptors in a developmentally regulated manner and thus, it is logical to hypothesize that perinatal exposure to buprenorphine could affect myelination. To investigate this possibility, pregnant rats were implanted with minipumps to deliver buprenorphine at 0.3 or 1 mg/kg/day. Analysis of their pups at different postnatal ages indicated that exposure to 0.3 mg/kg/day buprenorphine caused an accelerated and significant increase in the brain expression of all myelin basic protein (MBP) splicing isoforms. In contrast, treatment with the higher dose caused a developmental delay in MBP expression. Examination of corpus callosum at 26-days of age indicated that both buprenorphine doses cause a significant increase in the caliber of the myelinated axons. Surprisingly, these axons have a disproportionately thinner myelin sheath, suggesting alterations at the level of axon-glial interactions. Analysis of myelin associated glycoprotein (MAG) expression and glycosylation indicated that this molecule may play a crucial role in mediating these effects. Co-immunoprecipitation studies also suggested a mechanism involving a MAG-dependent activation of the Src-family tyrosine kinase Fyn. These results support the idea that opioid signaling plays an important role in regulating myelination in vivo and stress the need for further studies investigating potential effects of perinatal buprenorphine exposure on brain development.

The effects of maternally administered methadone, buprenorphine and naltrexone on offspring: review of human and animal data

Most women using heroin are of reproductive age with major risks for their infants. We review clinical and experimental data on fetal, neonatal and postnatal complications associated with methadone, the current "gold standard", and compare these with more recent, but limited, data on developmental effects of buprenorphine, and naltrexone. Methadone is a micro-opioid receptor agonist and is commonly recommended for treatment of opioid dependence during pregnancy. However, it has undesired outcomes including neonatal abstinence syndrome (NAS). Animal studies also indicate detrimental effects on growth, behaviour, neuroanatomy and biochemistry, and increased perinatal mortality. Buprenorphine is a partial micro-opioid receptor agonist and a kappa-opioid receptor antagonist. Clinical observations suggest that buprenorphine during pregnancy is similar to methadone on developmental measures but is potentially superior in reducing the incidence and prognosis of NAS. However, small animal studies demonstrate that low doses of buprenorphine during pregnancy and lactation lead to changes in offspring behaviour, neuroanatomy and biochemistry. Naltrexone is a non-selective opioid receptor antagonist. Although data are limited, humans treated with oral or sustained-release implantable naltrexone suggest outcomes potentially superior to those with methadone or buprenorphine. However, animal studies using oral or injectable naltrexone have shown developmental changes following exposure during pregnancy and lactation, raising concerns about its use in humans. Animal studies using chronic exposure, equivalent to clinical depot formulations, are required to evaluate safety. While each treatment is likely to have maternal advantages and disadvantages, studies are urgently required to determine which is optimal for offspring in the short and long term.

Cholinergic circuits and signaling in the pathophysiology of schizophrenia

Central cholinergic signaling has long been associated with aspects of memory, motivation, and mood, each affected functions in neuropsychiatric disorders such as schizophrenia. In this chapter, we review evidence related to the core hypothesis that dysregulation of central cholinergic signaling contributes to the pathophysiology of schizophrenia. Although central cholinergic circuits are resistant to simplification-particularly when one tries to parse the contributions of various classes of cholinergic receptors to disease related phenomena--the potential role of ACh signaling in Schizophrenia pathophysiology deserves careful consideration for prospective therapeutics. The established role of cholinergic circuits in attentional tuning is considered along with recent work on how the patterning of cholinergic activity may modulate corticostriatal circuits affected in schizophrenia.

Buprenorphine-containing treatments: place in the management of opioid addiction

Although the synthetic opioid buprenorphine has been available clinically for almost 30 years, its use has only recently become much more widespread for the treatment of opioid addiction. The pharmacodynamic and pharmacokinetic profiles of buprenorphine make it unique in the armamentarium of drugs for the treatment of opioid addiction. Buprenorphine has partial mu-opioid receptor agonist activity and is a kappa-opioid receptor antagonist; hence, it can substitute for other micro-opioid receptor agonists, yet is less apt to produce overdose reactions or dysphoria. On the other hand, buprenorphine can block the effects of opioids such as heroin (diamorphine) and morphine, and can even precipitate withdrawal in individuals physically dependent upon these drugs. Buprenorphine has significant sublingual bioavailability and a long half-life, making administration on a less than daily basis possible. Furthermore, its discontinuation is associated with only a mild withdrawal syndrome. Clinical trials have demonstrated that sublingual buprenorphine is effective in both maintenance therapy and detoxification of individuals addicted to opioids. The introduction of a sublingual formulation combining naloxone with buprenorphine further reduces the risk of diversion to illicit intravenous use. Because of its relative safety and lower risk of illegal diversion, buprenorphine has been made available in several countries for treating opioid addiction in the private office setting, greatly enhancing treatment options for this condition.

β-Phenylethylamines and the isoquinoline alkaloids

This review covers beta-phenylethylamines and isoquinoline alkaloids derived from them, including further products of oxidation. condensation with formaldehyde and rearrangement, some of which do not contain an isoquinoline system, together with naphthylisoquinoline alkaloids, which have a different biogenetic origin. The occurrence of the alkaloids, with the structures of new bases, together with their reactions, syntheses and biological activities are reported. The literature from July 2002 to June 2003 is reviewed, with 568 references cited.

Buprenorphine: an analgesic with an expanding role in the treatment of opioid addiction

Buprenorphine, a long-acting opioid with both agonist and antagonist properties, binds to mu-opioid (OP(3)), kappa-opioid (OP(2)), delta-opioid (OP(1)), and nociceptin (ORL-1) receptors. Its actions at these receptors have not been completely characterized, although buprenorphine is generally regarded as a mu-opioid receptor partial agonist and a kappa-opioid receptor antagonist. Its pharmacology is further complicated by an active metabolite, norbuprenorphine. Although buprenorphine can be used as an analgesic agent, it is of greater importance in the treatment of opioid abuse. Because of its partial agonist activity at mu-opioid receptors and its long half-life, buprenorphine has proven to be an excellent alternative to methadone for either maintenance therapy or detoxification of the opioid addict. Although buprenorphine may ultimately prove to be superior to methadone in the maintenance of the pregnant addict, its effects on the developing fetus must be carefully evaluated.