Long-time effects of prenatal morphine, tramadol, methadone, and buprenorphine exposure on seizure and anxiety in immature rats

Prenatal exposure to methadone or buprenorphine alters transcriptional networks associated with synaptic signaling in newborn rats

While the use of methadone or buprenorphine during pregnancy is beneficial for the mother's health compared to illicit opioid use, prenatal exposure to these medications may have adverse consequences for the unborn child. However, the underlying molecular mechanisms of prenatal opioid exposure on neurodevelopment remain poorly understood. Hence, this study aimed to investigate gene expression changes, focusing on synapse-related genes, in cerebral tissue from newborn rats prenatally exposed to methadone or buprenorphine. Female Sprague-Dawley rats were exposed to methadone (10 mg/kg/day), buprenorphine (1 mg/kg/day), or sterile water through osmotic minipumps during pregnancy. Total RNA was isolated from the cerebrum on postnatal day 2 and analyzed using RNA-sequencing. Analyses of differentially expressed genes (DEGs) and enriched biological processes were conducted to compare the gene expression profiles between treatment groups within each sex. Prenatal buprenorphine exposure resulted in 598 DEGs (333 up- and 265 downregulated) in males and 175 (75 up- and 100 downregulated) in females, while prenatal methadone exposure resulted in 335 DEGs (224 up- and 111 downregulated) in males and 201 (57 up- and 144 downregulated) in females. Gene ontology analyses demonstrated that enriched biological processes included synaptic signaling, immune responses, and apoptosis. Analysis of the DEGs using the synapse database SynGO revealed that males prenatally exposed to buprenorphine displayed the highest number of enriched synapse-related biological process terms. Understanding gene expression changes following prenatal methadone or buprenorphine exposure is crucial to uncover the mechanisms underlying behavioral alterations and to develop interventions to mitigate the impact of opioid exposure on neurodevelopment.

Perinatal exposure to methadone or buprenorphine impairs hippocampal-dependent cognition and brain development in juvenile rats

The opioid crisis continues to escalate, disproportionately affecting women of reproductive age. Traditionally the first line of treatment for pregnant women with opioid use disorder is the mu-opioid receptor agonist methadone. However, in recent years, the use of buprenorphine as a replacement therapy has increased as it has fewer side-effects and longer duration of action. Either drug significantly improves outcomes for the mother, but their impact on the developing infant is less certain. To this end, we directly compared the effects of perinatal methadone (MET; 9 mg/kg/day starting dose) versus buprenorphine (BUP; 1 mg/kg/day starting dose) delivered via mini osmotic pump on the long-term behavior of offspring and associated molecular changes in the brain. Opioid exposure across pregnancy resulted in reduced weight gain and smaller litters compared to sham controls, and female pups in particular gained weight at a slower rate across development. Opioid treatment delayed neuromuscular reflex development, with subtle differences observed between MET and BUP. As juveniles, pups with prenatal MET exposure showed poor object recognition, although both MET and BUP have led to deficits in place recognition task. Immunofluorescence studies found corresponding decreases in astrocytes and myelin-positive cells in the hippocampus in both MET and BUP pups. Overall, both MET and BUP were associated with significant developmental and cognitive delays and changes in markers of neuronal development and inflammation, particularly in the hippocampus. The majority of changes were similar between MET and BUP-treated pups, suggesting that gestational exposure to either drug has a similar long-term negative impact on offspring.

Effects of prenatal exposure to methadone or buprenorphine and maternal separation on anxiety-like behavior in rats

BACKGROUND

The use of medications for opioid use disorder such as methadone or buprenorphine is increasing among pregnant women. However, long-term effects of this treatment on the children's health are not well understood. A key challenge is distinguishing the effects of opioid exposure from other confounding factors associated with human opioid use, such as reduced maternal care. In this study, we therefore used a multi-risk factor design to examine anxiety-like behavior in rats prenatally exposed to methadone or buprenorphine, with or without maternal separation the first two weeks after birth.

METHODS

Female Sprague Dawley rats were exposed to methadone (10mg/kg/day), buprenorphine (1mg/kg/day) or sterile water throughout gestation. Half of the offspring in each litter experienced maternal separation for 3h per day from postnatal day 2 to 12. Male and female offspring (6-9 weeks) were tested in the open field, light-dark transition and elevated plus maze tests to assess anxiety-like behavior.

RESULTS

Offspring exposed to buprenorphine and not subjected to maternal separation displayed increased anxiety-like behavior in 3 out of 6 outcomes in the light-dark transition and elevated plus maze tests. Maternal separation did not exacerbate, but rather diminished this behavior. Males and females responded differently to methadone, with a trend towards reduced anxiety for males and increased anxiety for females.

CONCLUSIONS

Prenatal exposure to methadone or buprenorphine may increase the risk of developing anxiety-like behavior later in life, but the effect depends on specific subgroup characteristics. Further research is required to draw definitive conclusions.

GABA system as the cause and effect in early development

GABA is the primary inhibitory neurotransmitter in the adult brain and through its actions on GABAARs, it protects against excitotoxicity and seizure activity, ensures temporal fidelity of neurotransmission, and regulates concerted rhythmic activity of neuronal populations. In the developing brain, the development of GABAergic neurons precedes that of glutamatergic neurons and the GABA system serves as a guide and framework for the development of other brain systems. Despite this early start, the maturation of the GABA system also continues well into the early postnatal period. In this review, we organize evidence around two scenarios based on the essential and protracted nature of GABA system development: 1) disruptions in the development of the GABA system can lead to large scale disruptions in other developmental processes (i.e., GABA as the cause), 2) protracted maturation of this system makes it vulnerable to the effects of developmental insults (i.e., GABA as the effect). While ample evidence supports the importance of GABA/GABAAR system in both scenarios, large gaps in existing knowledge prevent strong mechanistic conclusions.

Uniform cerebral organoid culture on a pillar plate by simple and reproducible spheroid transfer from an ultralow attachment well plate

Human induced pluripotent stem cell (iPSC)-derived brain organoids have potential to recapitulate the earliest stages of brain development, serving as an effectivein vitromodel for studying both normal brain development and disorders. However, current brain organoid culture methods face several challenges, including low throughput, high variability in organoid generation, and time-consuming, multiple transfer and encapsulation of cells in hydrogels throughout the culture. These limitations hinder the widespread application of brain organoids including high-throughput assessment of compounds in clinical and industrial lab settings. In this study, we demonstrate a straightforward approach of generating multiple cerebral organoids from iPSCs on a pillar plate platform, eliminating the need for labor-intensive, multiple transfer and encapsulation steps to ensure the reproducible generation of cerebral organoids. We formed embryoid bodies in an ultra-low attachment 384-well plate and subsequently transferred them to the pillar plate containing Matrigel, using a straightforward sandwiching and inverting method. Each pillar on the pillar plate contains a single spheroid, and the success rate of spheroid transfer was in a range of 95%-100%. Using this approach, we robustly generated cerebral organoids on the pillar plate and demonstrated an intra-batch coefficient of variation below 9%-19% based on ATP-based cell viability and compound treatment. Notably, our spheroid transfer method in combination with the pillar plate allows miniaturized culture of cerebral organoids, alleviates the issue of organoid variability, and has potential to significantly enhance assay throughput by allowingin situorganoid assessment as compared to conventional organoid culture in 6-/24-well plates, petri dishes, and spinner flasks.

Influence of methadone on the anticonvulsant efficacy of valproate sodium gabapentin against maximal electroshock seizure in mice by regulation of brain MDA TNF-α

Methadone is the most frequently used opioid therapy worldwide, with controversial effects on oxidative stress homeostasis. This study investigated the effects of intraperitoneal (i.p.) co-administration of methadone (0.1, 0.3, 1, and 3 mg/kg) and valproate sodium (300 mg/kg) or gabapentin (50 mg/kg) in the mice maximal electroshock (MES)-induced seizure model. The adverse effect of drugs was assessed using the chimney test. The levels of tumor necrosis factor-alpha (TNF-α) and malondialdehyde (MDA) contents were measured in mice brains after a single seizure. Administration of methadone alone resulted in a significant reduction in the duration of hind limb extension (HLE) than that in the control group. Methadone pretreatment at doses of 0.1 and 0.3 mg/kg i.p. decreased, and at doses of 1 and 3 mg/kg i.p. had an increasing effect on anticonvulsant efficacy of gabapentin. Pretreatment with all doses of methadone significantly decreased the valproate anticonvulsive efficacy. At doses of 1 and 3 mg/kg i.p. methadone per se increased brain MDA levels after MES-induced seizure. Administration of methadone (0.3 mg/kg i.p.) enhanced and at 3 mg/kg decreased gabapentin effect on brain MDA level, but their co-treatment did not lead to further increase in MDA. Methadone at 0.3–3 mg/kg enhanced the effect of sodium valproate on MDA levels in the brain, but at all doses significantly potentiated its effect on brain TNF-α levels. The drugs did not produce any side effects on motor coordination in experimental animals. In conclusion, methadone showed different effects on anticonvulsant actions of gabapentin and valproate through regulation of brain levels of MDA and TNF-α.

Prenatal Morphine Exposure Differentially Alters Addictive and Emotional Behavior in Adolescent and Adult Rats in a Sex-Specific Manner

The effects of prenatal opioid exposure in adult animals has been widely studied, but little is known about the effects of prenatal opioid on adolescents. Most of the risk behaviors associated with drug abuse are initiated during adolescence. The developmental state of the adolescent brain makes it vulnerable to initiate drug use and susceptible to drug-induced brain changes. In this study, pregnant rats were subcutaneously injected with an increasing dose of morphine (5 mg/kg, 7 mg/kg, 10 mg/kg) for 9 days since the gestation day 11. The effects of prenatal morphine (PNM) on learning and memory, anxiety- and depressive- like behavior, morphine induced conditioned place preference (CPP) as well as locomotor sensitization were tested in both adolescent and adult rats. The results showed that: (1) PNM decreased anxiety-like behavior in both adolescent and adult female rats, but not males; (2) PNM decreased depressive-like behavior in adolescent but increased depressive -like behavior in adult females; (3) PNM increased low dose morphine induced locomotor sensitization in females; (4) PNM decreased tyrosine hydroxylase (TH) expression in the prefrontal cortex but decreased dopamine D1 receptor expression in the nucleus-accumbens (NAc) in female rats. These results suggested that PNM altered the emotional and addictive behavior mainly in female rats, with female rats being less anxiety and depressive during adolescence, but more depressive in adult, and more sensitive to low dose morphine induced locomotor activity sensitization, which might be mediated in part by the differential expression of the TH, dopamine D1 receptors in the female brain.

Buprenorphine Exposure Alters the Development and Migration of Interneurons in the Cortex

The misuse of opioids has reached epidemic proportions over the last decade, with over 2.1 million people in the United States suffering from substance use disorders related to prescription opioid pain relievers. This increase in opioid misuse affects all demographics of society, including women of child-bearing age, which has led to a rise in opioid use during pregnancy. Opioid use during pregnancy has been associated with increased risk of obstetric complications and adverse neonatal outcomes, including neonatal abstinence syndrome. Currently, opioid use disorder in pregnant women is treated with long-acting opioid agonists, including buprenorphine. Although buprenorphine reduces illicit opioid use during pregnancy and improves infant outcomes at birth, few long-term studies of the neurodevelopmental consequences have been conducted. The goal of the current experiments was to examine the effects of buprenorphine on the development of the cortex using fetal brain tissue, 3D brain cultures, and rodent models. First, we demonstrated that we can grow cortical and subpallial spheroids, which model the cellular diversity, connectivity, and activity of the developing human brain. Next, we show that cells in the developing human cortex express the nociceptin opioid (NOP) receptor and that buprenorphine can signal through this receptor in cortical spheroids. Using subpallial spheroids to grow inhibitory interneurons, we show that buprenorphine can alter interneuron development and migration into the cortex. Finally, using a rodent model of prenatal buprenorphine exposure, we demonstrate that alterations in interneuron distribution can persist into adulthood. Together, these results suggest that more research is needed into the long-lasting consequences of buprenorphine exposure on the developing human brain.

Effect of Methadone and Tramadol Opioids on Stem Cells Based on Integrated Plasmonic-Ellipsometry Technique

Introduction: Plasmonic biosensors provide high sensitivity in detecting the low amount of biomarkers and pharmaceutical drugs. We studied the mesenchyme cell activity under the treatment of common sedative drugs of methadone and tramadol using the integrated plasmonic-ellipsometry technique. Methods: Mesenchymal stem cells were cultured on patterned plasmonic chips under the treatment of methadone and tramadol drugs. Three cultured chips were kept non-treated as the control ones. The plasmonic-ellipsometry technique was applied to study the signaling characteristic of the cells affected by these two drugs. In this technique, optical information regarding the amplitude ratio and phase change between p- and s-polarized light was recorded. Results: This drug treatment could affect the spectral plasmonic resonance and subsequently the phase shift (Δ) and the amplitude ratio (Ψ) values under p- and s-polarized impinging light. A more significant Δ value for tramadol treatment meant that the phase split was larger between p- and s-polarized light. Tramadol also had more prominent absolute Δ eff and Ψ eff values in comparison with methadone. Conclusion: We showed that tramadol caused more contrast in phase shift (Δ) and amplitude ratio (Ψ) between p- and s-polarized impinging light for cultured stem cells in comparison with methadone. It means that tramadol differentiated more the optical responses for p- and s-polarized lights compared to methadone. Our proposed technique possesses the potential of quantitative and qualitative analysis of drugs on humans even on a cell scale.

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.