SnapShot: Neurobiology of opioid use disorder.

The use of opioid drugs and related overdose deaths, which rose to epidemic proportions over the past decade, have been exacerbated by the COVID pandemic, a time of great uncertainty and isolation. Much is known about opioid pharmacology and related neural circuits that, combined with novel emerging neurobiological insights, can help guide new treatment strategies. To view this SnapShot, open or download the PDF.

Cannabis and synaptic reprogramming of the developing brain.

Recent years have been transformational in regard to the perception of the health risks and benefits of cannabis with increased acceptance of use. This has unintended neurodevelopmental implications given the increased use of cannabis and the potent levels of Δ9-tetrahydrocannabinol today being consumed by pregnant women, young mothers and teens. In this Review, we provide an overview of the neurobiological effects of cannabinoid exposure during prenatal/perinatal and adolescent periods, in which the endogenous cannabinoid system plays a fundamental role in neurodevelopmental processes. We highlight impaired synaptic plasticity as characteristic of developmental exposure and the important contribution of epigenetic reprogramming that maintains the long-term impact into adulthood and across generations. Such epigenetic influence by its very nature being highly responsive to the environment also provides the potential to diminish neural perturbations associated with developmental cannabis exposure.

Reflections on the past two decades of neuroscience.

The first issue of Nature Reviews Neuroscience was published 20 years ago, in 2000. To mark this anniversary, in this Viewpoint article we asked a selection of researchers from across the field who have authored pieces published in the journal in recent years for their thoughts on notable and interesting developments in neuroscience, and particularly in their areas of the field, over the past two decades. They also provide some thoughts on current lines of research and questions that excite them.

Δ9-Tetrahydrocannabinol inhibits Hedgehog-dependent patterning during development.

Many developmental disorders are thought to arise from an interaction between genetic and environmental risk factors. The Hedgehog (HH) signaling pathway regulates myriad developmental processes, and pathway inhibition is associated with birth defects, including holoprosencephaly (HPE). Cannabinoids are HH pathway inhibitors, but little is known of their effects on HH-dependent processes in mammalian embryos, and their mechanism of action is unclear. We report that the psychoactive cannabinoid Δ9-tetrahydrocannabinol (THC) induces two hallmark HH loss-of-function phenotypes (HPE and ventral neural tube patterning defects) in Cdon mutant mice, which have a subthreshold deficit in HH signaling. THC therefore acts as a 'conditional teratogen', dependent on a complementary but insufficient genetic insult. In vitro findings indicate that THC is a direct inhibitor of the essential HH signal transducer smoothened. The canonical THC receptor, cannabinoid receptor-type 1, is not required for THC to inhibit HH signaling. Cannabis consumption during pregnancy may contribute to a combination of risk factors underlying specific developmental disorders. These findings therefore have significant public health relevance.

Dose mediates the protracted effects of adolescent THC exposure on reward and stress reactivity in males relevant to perturbation of the basolateral amygdala transcriptome.

Despite the belief that cannabis is relatively harmless, exposure during adolescence is associated with increased risk of developing several psychopathologies in adulthood. In addition to the high levels of use amongst teenagers, the potency of ∆-9-tetrahydrocannabinol (THC) has increased more than fourfold compared to even twenty years ago, and it is unclear whether potency influences the presentation of THC-induced behaviors. Expanded knowledge about the impact of adolescent THC exposure, especially high dose, is important to delineating neural networks and molecular mechanisms underlying psychiatric risk. Here, we observed that repeated exposure to low (1.5 mg/kg) and high (5 mg/kg) doses of THC during adolescence in male rats produced divergent effects on behavior in adulthood. Whereas low dose rats showed greater sensitivity to reward devaluation and also self-administered more heroin, high dose animals were significantly more reactive to social isolation stress. RNA sequencing of the basolateral amygdala, a region linked to reward processing and stress, revealed significant perturbations in transcripts and gene networks related to synaptic plasticity and HPA axis that were distinct to THC dose as well as stress. In silico single-cell deconvolution of the RNAseq data revealed a significant reduction of astrocyte-specific genes related to glutamate regulation in stressed high dose animals, a result paired anatomically with greater astrocyte-to-neuron ratios and hypotrophic astrocytes. These findings emphasize the importance of dose and behavioral state on the presentation of THC-related behavioral phenotypes in adulthood and dysregulation of astrocytes as an interface for the protracted effects of high dose THC and subsequent stress sensitivity.

Maternal cannabis use is associated with suppression of immune gene networks in placenta and increased anxiety phenotypes in offspring.

While cannabis is among the most used recreational drugs during pregnancy, the impact of maternal cannabis use (mCB) on fetal and child development remains unclear. Here, we assessed the effects of mCB on psychosocial and physiological measures in young children along with the potential relevance of the in utero environment reflected in the placental transcriptome. Children (∼3 to 6 y) were assessed for hair hormone levels, neurobehavioral traits on the Behavioral Assessment System for Children (BASC-2) survey, and heart rate variability (HRV) at rest and during auditory startle. For a subset of children with behavioral assessments, placental specimens collected at birth were processed for RNA sequencing. Hair hormone analysis revealed increased cortisol levels in mCB children. In addition, mCB was associated with greater anxiety, aggression, and hyperactivity. Children with mCB also showed a reduction in the high-frequency component of HRV at baseline, reflecting reduced vagal tone. In the placenta, there was reduced expression of many genes involved in immune system function including type I interferon, neutrophil, and cytokine-signaling pathways. Finally, several of these mCB-linked immune genes organized into coexpression networks that correlated with child anxiety and hyperactivity. Overall, our findings reveal a relationship between mCB and immune response gene networks in the placenta as a potential mediator of risk for anxiety-related problems in early childhood.

Response to uncertainty in developmental origins of health and disease research: commentary on Nomura et al. (2022).

We appreciate the comments of Gilman et al. (2023) on our paper and their acknowledgement of its importance in highlighting the significance of this area of research. Further, their acknowledgment that the primary results of our study are in a range that is similar to those from other published studies of children exposed to highly stressful environmental events emphasizes the validity of our findings and the important extension of our results to children experiencing these events in utero. They, however, raised concerns about some of the results regarding specific types of psychiatric disorders and sex-specific results related to the prenatal Superstorm Sandy hurricane exposure. We comment on the various issues related to the paper below but will not respond to comments regarding the press coverage of this article, which we think are beyond the scope of this commentary.

Prenatal exposure to a natural disaster and early development of psychiatric disorders during the preschool years: stress in pregnancy study.

BACKGROUND: Growing evidence shows an association between in utero exposure to natural disasters and child behavioral problems, but we still know little about the development of specific psychopathology in preschool-aged children. METHODS: Preschool children (n = 163, mean age = 3.19, 85.5% racial and ethnic minorities) and their parents (n = 151) were evaluated annually at ages 2-5 to assess the emergence of psychopathology using the Preschool Age Psychopathological Assessment (PAPA), a parent-report structured diagnostic interview developed for preschool-age children. Sixty-six (40.5%) children were exposed to Sandy Storm (SS) in utero and 97 (59.5%) were not. Survival analysis evaluated patterns of onset and estimated cumulative risks of psychopathology among exposed and unexposed children, in total and by sex. Analyses were controlled for the severity of objective and subjective SS-related stress, concurrent family stress, and demographic and psychosocial confounders, such as maternal age, race, SES, maternal substance use, and normative prenatal stress. RESULTS: Exposure to SS in utero was associated with a substantial increase in depressive disorders (Hazard Ratio (HR) = 16.9, p = .030), anxiety disorders (HR = 5.1, p < .0001), and attention-deficit/disruptive behavioral disorders (HR = 3.4, p = .02). Diagnostic rates were elevated for generalized anxiety disorder (GAD; HR = 8.5, p = .004), attention-deficit/hyperactivity disorder (ADHD; HR = 5.5, p = .01), oppositional-defiant disorder (ODD; HR = 3.8, p = .05), and separation-anxiety disorder (SAD; HR = 3.5, p = .001). Males had distinctively elevated risks for attention-deficit/disruptive behavioral disorders (HR = 7.8, p = .02), including ADHD, CD, and ODD, whereas females had elevated risks for anxiety disorders (HR = 10.0, p < .0001), phobia (HR = 2.8, p = .02) and depressive disorders (HR = 30.0, p = .03), including SAD, GAD, and dysthymia. CONCLUSIONS: The findings demonstrate that in utero exposure to a major weather-related disaster (SS) was associated with increased risk for psychopathology in children and provided evidence of distinct psychopathological outcomes as a function of sex. More attention is needed to understand specific parent, child, and environmental factors which account for this increased risk, and to develop mitigation strategies.

Dysregulated expression of the alternatively spliced variant mRNAs of the mu opioid receptor gene, OPRM1, in the medial prefrontal cortex of male human heroin abusers and heroin self-administering male rats.

Heroin, a mu agonist, acts through the mu opioid receptor. The mu opioid receptor gene, OPRM1, undergoes extensive alternative splicing, creating an array of splice variants that are conserved from rodent to humans. Increasing evidence suggests that these OPRM1 splice variants are pharmacologically important in mediating various actions of mu opioids, including analgesia, tolerance, physical dependence, rewarding behavior, as well as addiction. In the present study, we examine expression of the OPRM1 splice variant mRNAs in the medial prefrontal cortex (mPFC), one of the major brain regions involved in decision-making and drug-seeking behaviors, of male human heroin abusers and male rats that developed stable heroin-seeking behavior using an intravenous heroin self-administration (SA) model. The results show similar expression profiles among multiple OPRM1 splice variants in both human control subjects and saline control rats, illustrating conservation of OPRM1 alternative splicing from rodent to humans. Moreover, the expressions of several OPRM1 splice variant mRNAs were dysregulated in the postmortem mPFCs from heroin abusers compared to the control subjects. Similar patterns were observed in the rat heroin SA model. These findings suggest potential roles of the OPRM1 splice variants in heroin addiction that could be mechanistically explored using the rat heroin SA model.

Placental gene network modules are associated with maternal stress during pregnancy and infant temperament.

Maternal psychosocial stress during pregnancy (MPSP) is a known contributor to maladaptive neurobehavioral development of the offspring; however, the underlying molecular mechanisms linking MPSP with childhood outcome remain largely unknown. Transcriptome-wide gene expression data were generated using RNA-seq from placenta samples collected in a multi-ethnic urban birth cohort in New York City (n = 129). Weighted gene co-expression network analysis (WGCNA) was used to characterize placental co-expression modules, which were then evaluated for their associations with MPSP and infant temperament. WGCNA revealed 16 gene coexpression modules. One module, enriched for regulation of chromosome organization/gene expression, was positively associated with MPSP and negatively associated with Regulatory Capacity (REG), a component of infant temperament. Two other modules, enriched for cotranslational protein targeting and cell cycle regulation, respectively, displayed negative associations with MPSP and positive associations with REG. A module enriched with oxidative phosphorylation/mitochondrial translation was positively associated with REG. These findings support the notion that the placenta provides a functional in utero link between MPSP and infant temperament, possibly through transcriptional regulation of placental gene expression.

Natural disaster stress during pregnancy is linked to reprogramming of the placenta transcriptome in relation to anxiety and stress hormones in young offspring.

Prenatal stress can lead to long-term adverse effects that increase the risk of anxiety and other emotional disorders in offspring. The in utero underpinnings contributing to such phenotypes remain unknown. We profiled the transcriptome of placental specimens from women who lived through Hurricane Sandy during pregnancy compared to those pregnant during non-Sandy conditions. Following birth, longitudinal assessments were conducted in their offspring during childhood (~3-4 years old) to measure steroid hormones (in hair) and behavioral and emotional problems. This revealed a significant link between prenatal Sandy stress (PNSS) and child HPA dysfunction, evident by altered cortisol, dehydroepiandrosterone (DHEA), and cortisol:DHEA levels. In addition, PNSS was associated with significantly increased anxiety and aggression. These findings coincided with significant reorganization of the placental transcriptome via vascular, immune, and endocrine gene pathways. Interestingly, many of the most prominently altered genes were known to be uniquely expressed in syncytiotrophoblast (STB)-subtype of placental cells and harbored glucocorticoid response elements in promoter regions. Finally, several vascular development- and immune-related placental gene sets were found to mediate the relationship between PNSS and childhood phenotypes. Overall, these findings suggest that natural disaster-related stress during pregnancy reprograms the placental molecular signature, potentially driving long-lasting changes in stress regulation and emotional health. Further examination of placental mechanisms may elucidate the environment's contribution to subsequent risk for anxiety disorders later in life.

Stress in pregnancy: Clinical and adaptive behavior of offspring following Superstorm Sandy.

The current study investigated 304 children from a longitudinal project (the Stress in Pregnancy (SIP) Study) who were exposed and unexposed to Superstorm Sandy ("Sandy") in utero. They were prospectively followed from 2 to 6 years of age and their clinical and adaptive behaviors were assessed annually. Using a hierarchical linear model, the study found that in utero Sandy exposure was associated with greater clinical (anxiety, depression, and somatization) and lower adaptive behaviors (social skills and functional communication) at age 2 years. However, the trajectories were notably different between the two groups. Anxiety increased more rapidly among the exposed than unexposed group at ages 2-4, and depression increased only among the exposed. In contrast, social skills and functional communication were lower in exposed compared to unexposed children at age 2, but quickly increased and exceeded the capacities of unexposed children by age 3. The findings confirm that prenatal Sandy exposure is not only associated with an increase in anxiety, depression, and somatization in offspring, but also with greater adaptive skills as the children got older. Our study demonstrates that while children who have experienced stress in utero demonstrate elevated suboptimal clinical behaviors related to affective disorders, they nevertheless have the potential to learn adaptive skills.

Data mining-based clinical profiles of substance use-related emergency department utilizers.

OBJECTIVE: Substance-use is a prevalent presentation to the emergency department (ED); however, the clinical characterization of patients who are treated and discharged without admission for further treatment is under-investigated. The study aims to define and characterize the clinical profiles of this patient population. METHODS: Patients' presentations were examined by clinical data mining (chart review) of ED records of substance use-related events of individuals discharged without admission for further treatment. Records (N = 199) from three major hospitals in New York City from March and June 2017 were randomly sampled with primary diagnosis of alcohol, opioid-related and other psychoactive substance-use presentations. Qualitative thematic coding of clinical presentation with inter-rater reliability was performed. Quantitative distinctive validity tested independence through Pearson's chi-squared and analysis of variance using Fisher's F-test. RESULTS: Six distinct clinical profiles were identified, including, High Utilizers (chronically intoxicated with comorbid health conditions) (36.7%), Single Episode (20.1%), Service Request (14.1%), Altered Mental Status (13.6%), Overdose (9.0%), and Withdrawal (7.5%). The profiles differed (p < 0.05) in age, housing status, payor, mode of arrival, referral source, index visit time, prescribed treatment, triage acuity level, psychiatric history, and medical history. Differences (p < 0.05) between groups across clinical profiles in age and pain level at triage were observed. CONCLUSIONS: The identified clinical profiles represent the broad spectrum and complex nature of substance use-related ED utilization, highlighting critical factors of psychosocial and mental-health comorbidities. These findings provide a preliminary foundation to support person-centered interventions to decrease substance use-related ED utilization and to increase engagement/linkage of patients to addiction treatment.

An atlas of chromatin accessibility in the adult human brain.

Most common genetic risk variants associated with neuropsychiatric disease are noncoding and are thought to exert their effects by disrupting the function of cis regulatory elements (CREs), including promoters and enhancers. Within each cell, chromatin is arranged in specific patterns to expose the repertoire of CREs required for optimal spatiotemporal regulation of gene expression. To further understand the complex mechanisms that modulate transcription in the brain, we used frozen postmortem samples to generate the largest human brain and cell-type-specific open chromatin data set to date. Using the Assay for Transposase Accessible Chromatin followed by sequencing (ATAC-seq), we created maps of chromatin accessibility in two cell types (neurons and non-neurons) across 14 distinct brain regions of five individuals. Chromatin structure varies markedly by cell type, with neuronal chromatin displaying higher regional variability than that of non-neurons. Among our findings is an open chromatin region (OCR) specific to neurons of the striatum. When placed in the mouse, a human sequence derived from this OCR recapitulates the cell type and regional expression pattern predicted by our ATAC-seq experiments. Furthermore, differentially accessible chromatin overlaps with the genetic architecture of neuropsychiatric traits and identifies differences in molecular pathways and biological functions. By leveraging transcription factor binding analysis, we identify protein-coding and long noncoding RNAs (lncRNAs) with cell-type and brain region specificity. Our data provide a valuable resource to the research community and we provide this human brain chromatin accessibility atlas as an online database "Brain Open Chromatin Atlas (BOCA)" to facilitate interpretation.

Striatal Rgs4 regulates feeding and susceptibility to diet-induced obesity.

Consumption of high fat, high sugar (western) diets is a major contributor to the current high levels of obesity. Here, we used a multidisciplinary approach to gain insight into the molecular mechanisms underlying susceptibility to diet-induced obesity (DIO). Using positron emission tomography (PET), we identified the dorsal striatum as the brain area most altered in DIO-susceptible rats and molecular studies within this region highlighted regulator of G-protein signaling 4 (Rgs4) within laser-capture micro-dissected striatonigral (SN) and striatopallidal (SP) medium spiny neurons (MSNs) as playing a key role. Rgs4 is a GTPase accelerating enzyme implicated in plasticity mechanisms of SP MSNs, which are known to regulate feeding and disturbances of which are associated with obesity. Compared to DIO-resistant rats, DIO-susceptible rats exhibited increased striatal Rgs4 with mRNA expression levels enriched in SP MSNs. siRNA-mediated knockdown of striatal Rgs4 in DIO-susceptible rats decreased food intake to levels comparable to DIO-resistant animals. Finally, we demonstrated that the human Rgs4 gene locus is associated with increased body weight and obesity susceptibility phenotypes, and that overweight humans exhibit increased striatal Rgs4 protein. Our findings highlight a novel role for involvement of Rgs4 in SP MSNs in feeding and DIO-susceptibility.

Biomarkers of endothelial dysfunction in cocaine overdose and overdose-related cardiovascular events.

Overdose of stimulant drugs has been associated with increased risk of adverse cardiovascular events (ACVE), some of which may be ascribed to endothelial dysfunction. The aims of this study were to evaluate biomarkers of endothelial dysfunction in emergency department (ED) patients with acute cocaine overdose and to assess the association between in-hospital ACVE in ED patients with any acute drug overdose. This was a prospective consecutive cohort study over 9 months (2015-2016) at two urban, tertiary-care hospital EDs. Consecutive adults (≥18 years) presenting with suspected acute drug overdose were eligible and separated into three groups: cocaine (n = 47), other drugs (n = 128), and controls (n = 11). Data were obtained from medical records and linked to waste serum specimens, sent as part of routine clinical care, for biomarker analysis. Serum specimens were collected and analyzed using enzyme-linked immunosorbent assay kit for three biomarkers of endothelial dysfunction: (a) endothelin-1 (ET-1), (b) regulated upon activation normal T cell expressed and secreted (RANTES), and (c) soluble intercellular adhesion molecule-1 (siCAM-1). Mean siCAM was elevated for cocaine compared with controls and other drugs (p < .01); however, mean RANTES and ET-1 levels were not significantly different for any drug exposure groups. Receiver operating characteristics curve analysis for prediction of in-hospital ACVE revealed excellent performance of siCAM-1 (area under curve, 0.86; p < .001) but lack of predictive utility for either RANTES or ET-1. These results suggest that serum siCAM-1 is a viable biomarker for acute cocaine overdose and that endothelial dysfunction may be an important surrogate for adverse cardiovascular events following any drug overdose.

Cannabis and the Developing Brain: Insights into Its Long-Lasting Effects.

The recent shift in sociopolitical debates and growing liberalization of cannabis use across the globe has raised concern regarding its impact on vulnerable populations, such as pregnant women and adolescents. Epidemiological studies have long demonstrated a relationship between developmental cannabis exposure and later mental health symptoms. This relationship is especially strong in people with particular genetic polymorphisms, suggesting that cannabis use interacts with genotype to increase mental health risk. Seminal animal research directly linked prenatal and adolescent exposure to delta-9-tetrahydrocannabinol, the major psychoactive component of cannabis, with protracted effects on adult neural systems relevant to psychiatric and substance use disorders. In this article, we discuss some recent advances in understanding the long-term molecular, epigenetic, electrophysiological, and behavioral consequences of prenatal, perinatal, and adolescent exposure to cannabis/delta-9-tetrahydrocannabinol. Insights are provided from both animal and human studies, including in vivo neuroimaging strategies.

Synaptic Microtubule-Associated Protein EB3 and SRC Phosphorylation Mediate Structural and Behavioral Adaptations During Withdrawal From Cocaine Self-Administration.

Addictive behaviors, including relapse, are thought to depend in part on long-lasting drug-induced adaptations in dendritic spine signaling and morphology in the nucleus accumbens (NAc). While the influence of activity-dependent actin remodeling in these phenomena has been studied extensively, the role of microtubules and associated proteins remains poorly understood. We report that pharmacological inhibition of microtubule polymerization in the NAc inhibited locomotor sensitization to cocaine and contextual reward learning. We then investigated the roles of microtubule end-binding protein 3 (EB3) and SRC kinase in the neuronal and behavioral responses to volitionally administered cocaine. In synaptoneurosomal fractions from the NAc of self-administering male rats, the phosphorylation of SRC at an activating site was induced after 1 d of withdrawal, while EB3 levels were increased only after 30 d of withdrawal. Blocking SRC phosphorylation during early withdrawal by virally overexpressing SRCIN1, a negative regulator of SRC activity known to interact with EB3, abolished the incubation of cocaine craving in both male and female rats. Conversely, mimicking the EB3 increase observed after prolonged withdrawal increased the motivation to consume cocaine in male rats. In mice, the overexpression of either EB3 or SRCIN1 increased dendritic spine density and altered the spine morphology of NAc medium spiny neurons. Finally, a cocaine challenge after prolonged withdrawal recapitulated most of the synaptic protein expression profiles observed at early withdrawal. These findings suggest that microtubule-associated signaling proteins such as EB3 cooperate with actin remodeling pathways, notably SRC kinase activity, to establish and maintain long-lasting cellular and behavioral alterations following cocaine self-administration.SIGNIFICANCE STATEMENT Drug-induced morphological restructuring of dendritic spines of nucleus accumbens neurons is thought to be one of the cellular substrates of long-lasting drug-associated memories. The molecular basis of these persistent changes has remained incompletely understood. Here we implicate for the first time microtubule function in this process, together with key players such as microtubule-bound protein EB3 and synaptic SRC phosphorylation. We propose that microtubule and actin remodeling cooperate during withdrawal to maintain the plastic structural changes initially established by cocaine self-administration. This work opens new translational avenues for further characterization of microtubule-associated regulatory molecules as putative drug targets to tackle relapse to drug taking.

Endocannabinoid signalling in reward and addiction.

Brain endocannabinoid (eCB) signalling influences the motivation for natural rewards (such as palatable food, sexual activity and social interaction) and modulates the rewarding effects of addictive drugs. Pathological forms of natural and drug-induced reward are associated with dysregulated eCB signalling that may derive from pre-existing genetic factors or from prolonged drug exposure. Impaired eCB signalling contributes to dysregulated synaptic plasticity, increased stress responsivity, negative emotional states and cravings that propel addiction. Understanding the contributions of eCB disruptions to behavioural and physiological traits provides insight into the eCB influence on addiction vulnerability.

Molecular windows into the human brain for psychiatric disorders.

Delineating the pathophysiology of psychiatric disorders has been extremely challenging but technological advances in recent decades have facilitated a deeper interrogation of molecular processes in the human brain. Initial candidate gene expression studies of the postmortem brain have evolved into genome wide profiling of the transcriptome and the epigenome, a critical regulator of gene expression. Here, we review the potential and challenges of direct molecular characterization of the postmortem human brain, and provide a brief overview of recent transcriptional and epigenetic studies with respect to neuropsychiatric disorders. Such information can now be leveraged and integrated with the growing number of genome-wide association databases to provide a functional context of trait-associated genetic variants linked to psychiatric illnesses and related phenotypes. While it is clear that the field is still developing and challenges remain to be surmounted, these recent advances nevertheless hold tremendous promise for delineating the neurobiological underpinnings of mental diseases and accelerating the development of novel medication strategies.