Altering endocannabinoid neurotransmission at critical developmental ages: impact on rodent emotionality and cognitive performance

Prenatal cannabis exposure and the risk for neuropsychiatric anomalies in the offspring: a systematic review and meta-analysis

OBJECTIVE

To evaluate the association between cannabis use during pregnancy and the risk for long-term neuropsychiatric pathology in the offspring.

DATA SOURCES

MEDLINE, EMBASE, and Cochrane library databases were systematically searched until January 22, 2024, with no language or date restrictions.

STUDY ELIGIBILITY CRITERIA

Studies were eligible for inclusion if they reported quantitative data on any long-term neuropsychiatric outcome in offspring whose mothers used cannabis during pregnancy for medical or recreational use, by any route and at any trimester, in comparison to offspring of women who abstained from cannabis use during pregnancy. All observational study designs were included in the analysis.

STUDY APPRAISAL AND SYNTHESIS METHODS

A systematic review and meta-analysis were performed according to the PRISMA and MOOSE guidelines. The data was extracted independently by 2 reviewers. The following offspring outcomes were of interest: attention-deficit/hyperactivity disorder (ADHD), autism spectrum disorder (ASD), depression, anxiety, psychotic disorders, as well as cannabis and other substance use. Odds ratios (OR) and 95% confidence intervals (CI) were pooled for each neuropsychiatric outcome in the offspring of women exposed to cannabis during pregnancy compared with nonexposed. Data were pooled using random-effects models.

RESULTS

Eighteen eligible observational studies were included in the systematic review, and 17 were included in the final quantitative analysis, representing 534,445 participants. After adjusting for confounders, the pooled OR for ADHD was 1.13 (95% CI 1.01-1.26); for ASD, the pooled OR was 1.04 (95% CI 0.74-1.46); for psychotic symptoms, the pooled OR was 1.29 (95% CI 0.97-1.72); for anxiety, the pooled OR was 1.34 (95% CI 0.79-2.29); for depression, the pooled OR was 0.72 (95% CI 0.11-4.57); and for offspring's cannabis use, the pooled OR was 1.20 (95% CI 1.01-1.42).

CONCLUSION

Prenatal cannabis exposure is not associated with an increased risk of ASD, psychotic symptoms, anxiety, or depression in offspring. However, it may slightly elevate the risk of ADHD and predispose offspring to cannabis consumption. Despite these findings, caution is warranted regarding cannabis use during pregnancy. Further research is imperative, especially given the increasing potency of cannabis in recent years.

Prenatal cannabis use and the risk of attention deficit hyperactivity disorder and autism spectrum disorder in offspring: A systematic review and meta-analysis

BACKGROUND

It is plausible that exposure to cannabis in-utero could be associated with an increased risk of neurodevelopmental disorders such as attention deficit hyperactivity disorder (ADHD) symptoms and autism spectrum disorder (ASD) during childhood and adolescence; however, mixed results have been reported. This study investigated whether there is an association between prenatal cannabis use and ADHD symptoms and ASD in offspring using a systematic review and meta-analysis methodology.

METHODS

A systematic literature search was conducted in PubMed/Medline, Scopus, EMBASE, Web of Science, Psych-Info, and Google Scholar to identify relevant studies. The study protocol has been preregistered in the Prospective Register of Systematic Reviews (PROSPERO) (CRD42022345001), and the Newcastle-Ottawa Quality Assessment Scale (NOS) was used to assess the methodological quality of included studies. An inverse variance weighted random effect meta-analysis was conducted to pool the overall effect estimates from the included studies.

RESULTS

Fourteen primary studies, consisting of ten on ADHD and four on ASD, with a total of 203,783 participants, were included in this study. Our meta-analysis underscores an increased risk of ADHD symptoms and/or disorder [β = 0.39: 95 % CI (0.20-0.58), I2 = 66.85 %, P = 0.001)] and ASD [RR = 1.30: 95 % CI (1.03-1.64), I2 = 45.5 %, P = 0.14] associated with in-utero cannabis exposure in offspring compared to their non-exposed counterparts. Additionally, our stratified analysis highlighted an elevated risk of ADHD symptoms [β = 0.54: 95 % CI (0.26-0.82)] and a marginally significant increase in the risk of diagnostic ADHD among exposed offspring compared to non-exposed counterparts [RR = 1.13, 95 % CI (1.01, 1.26)].

CONCLUSION

This study indicated that maternal prenatal cannabis exposure is associated with a higher risk of ADHD symptoms and ASD in offspring.

Outcomes of early social experiences on glucocorticoid and endocannabinoid systems in the prefrontal cortex of male and female adolescent rats

Social and emotional experiences differently shape individual's neurodevelopment inducing substantial changes in neurobiological substrates and behavior, particularly when they occur early in life. In this scenario, the present study was aimed at (i) investigating the impact of early social environments on emotional reactivity of adolescent male and female rats and (ii) uncovering the underlying molecular features, focusing on the cortical endocannabinoid (eCB) and glucocorticoid systems. To this aim, we applied a protocol of environmental manipulation based on early postnatal socially enriched or impoverished conditions. Social enrichment was realized through communal nesting (CN). Conversely, an early social isolation (ESI) protocol was applied (post-natal days 14-21) to mimic an adverse early social environment. The two forms of social manipulation resulted in specific behavioral and molecular outcomes in both male and female rat offspring. Despite the combination of CN and ESI did not affect emotional reactivity in both sexes, the molecular results reveal that the preventive exposure to CN differently altered mRNA and protein expression of the main components of the glucocorticoid and eCB systems in male and female rats. In particular, adolescent females exposed to the combination of CN and ESI showed increased corticosterone levels, unaltered genomic glucocorticoid receptor, reduced cannabinoid receptor type-1 and fatty acid amide hydrolase protein levels, suggesting that the CN condition evokes different reorganization of these systems in males and females.

Prenatal alcohol and tetrahydrocannabinol exposure: Effects on spatial and working memory

Introduction

Alcohol and cannabis are widely used recreational drugs that can negatively impact fetal development, leading to cognitive impairments. However, these drugs may be used simultaneously and the effects of combined exposure during the prenatal period are not well understood. Thus, this study used an animal model to investigate the effects of prenatal exposure to ethanol (EtOH), Δ-9-tetrahydrocannabinol (THC), or the combination on spatial and working memory.

Methods

Pregnant Sprague-Dawley rats were exposed to vaporized ethanol (EtOH; 68 ml/h), THC (100 mg/ml), the combination, or vehicle control during gestational days 5-20. Adolescent male and female offspring were evaluated using the Morris water maze task to assess spatial and working memory.

Results

Prenatal THC exposure impaired spatial learning and memory in female offspring, whereas prenatal EtOH exposure impaired working memory. The combination of THC and EtOH did not exacerbate the effects of either EtOH or THC, although subjects exposed to the combination were less thigmotaxic, which might represent an increase in risk-taking behavior.

Discussion

Our results highlight the differential effects of prenatal exposure to THC and EtOH on cognitive and emotional development, with substance- and sex-specific patterns. These findings highlight the potential harm of THC and EtOH on fetal development and support public health policies aimed at reducing cannabis and alcohol use during pregnancy.

Emerging Roles of Endocannabinoids as Key Lipid Mediators for a Successful Pregnancy

In recent years, Cannabis use/misuse for treating pregnancy-related symptoms and other chronic conditions has increased among pregnant women, favored by decriminalization and/or legalization of its recreational uses in addition to its easy accessibility. However, there is evidence that prenatal Cannabis exposure might have adverse consequences on pregnancy progression and a deleterious impact on proper neurodevelopmental trajectories in the offspring. Maternal Cannabis use could interfere with the complex and finely controlled role performed by the endocannabinoid system in reproductive physiology, impairing multiple gestational processes from blastocyst implantation to parturition, with long-lasting intergenerational effects. In this review, we discuss current clinical and preclinical evidence regarding the role of endocannabinoids in development, function, and immunity of the maternal–fetal interface, focusing on the impact of Cannabis constituents on each of these gestational processes. We also discuss the intrinsic limitations of the available studies and the future perspectives in this challenging research field.

Is in-utero exposure to cannabis associated with the risk of attention deficit with or without hyperactivity disorder? A cohort study within the Quebec Pregnancy Cohort

IMPORTANCE AND OBJECTIVE

Prenatal cannabis effect on attention deficit with or without hyperactivity disorder (ADHD) remains to be determined. Our aim is to quantify the impact of in-utero exposure to cannabis on the risk of ADHD.

DESIGN

Cohort study.

SETTING

Questionnaires were mailed to women sampled from the Quebec Pregnancy Cohort (QPC). Data from questionnaires were then linked with their QPC (built with administrative health databases, hospital patient charts and birth certificate databases).

PARTICIPANTS

Respondents who gave birth to a singleton live born between January 1998 and December 2003 and were continuously enrolled in the Régie de l'assurance maladie du Québec (RAMQ) medication insurance plan for at least 12 months before the first day of gestation and during pregnancy.

EXPOSURE

In-utero cannabis exposure was based on mothers' answers to the question on cannabis use during pregnancy (yes/no) and categorised as occasionally, regularly exposed and unexposed if they chose one of these categories.

OUTCOMES

ADHD was defined by a diagnosis of ADHD through the RAMQ medical services or MedEcho databases or a prescription filled for ADHD medication through RAMQ pharmaceutical services between birth and the end of the follow-up period. Follow-up started at the birth and ended at the index date (first diagnosis or prescription filled for ADHD), child death (censoring), end of public coverage for medications (censoring) or the end of study period, which was December 2015 (censoring), whichever event came first.

RESULTS

A total of 2408 children met the inclusion criteria. Of these children, 86 (3.6%) were exposed to cannabis in-utero and 241 (10.0%) had an ADHD diagnosis or medication filled. After adjustments for potential confounders, no significant association was found between in-utero cannabis exposure (occasional (1.22 (95% CI 0.63 to 2.19)) or regular (1.22 (95% CI 0.42 to 2.79))) and the risk of ADHD in children.

CONCLUSIONS

In-utero exposure to cannabis seemed to not be associated with the risk ADHD in children.

Effects of Δ9-Tetrahydrocannibinol (THC) on Obesity at Different Stages of Life: A Literature Review

The Cannabis sativa plant has historically been used for both recreational and medical purposes. With the recent surge in recreational use of cannabis among adolescents and adults in particular, there is an increased obligation to determine the short- and long-term effects that consuming this plant may have on several aspects of the human psyche and body. The goal of this article was to examine the negative effects of obesity, and how the use of Δ9-tetrahydrocannibinol (THC) or cannabidiol (CBD) can impact rates of this global pandemic at different timepoints of life. Conflicting studies have been reported between adult and adolescents, as there are reports of THC use leading to increased weight due to elevated appetite and consumption of food, while others observed a decrease in overall body weight due to the regulation of omega-6/omega-3 endocannabinoid precursors and a decrease in energy expenditure. Studies supported a positive correlation between prenatal cannabis use and obesity rates in the children as they matured. The data did not indicate a direct connection between prenatal THC levels in cannabis and obesity rates, but that this development may occur due to prenatal THC consumption leading to low birthweight, and subsequent obesity. There are few studies using animal models that directly measure the effects that prenatal THC administration on obesity risks among offspring. Thus, this is a critical area for future studies using a developmental framework to examine potential changes in risk across development.

Long-term effects of prenatal cannabis exposure: Pathways to adolescent and adult outcomes

With the increased prevalence, potency, and acceptability of cannabis use during pregnancy, it is important to understand the developmental effects of prenatal cannabis exposure (PCE). This review discusses methodological considerations for studies of PCE, including the assessment of exposures, covariates, and outcomes, and reviews findings from prospective, longitudinal studies of PCE. There is some evidence for associations between PCE and restricted growth at birth, but not for long-term effects on growth. PCE appears to have subtle yet enduring effects on memory and achievement in children and adolescents. Despite differences in sample demographics and measurement, there are remarkably consistent effects of PCE on externalizing behaviors, such as delinquency and substance use, which persist into adulthood. Longitudinal analyses demonstrate the importance of early cannabis initiation for pathways between PCE and adult functioning, including substance use and abuse, memory deficits, and psychotic symptoms. Animal studies demonstrate direct effects on the development of the brain via activation of endogenous endocannabinoid systems. Cannabis-induced activation of the endocannabinoid system causes alterations in the release of neurotransmitters and the modulation of brain plasticity in neural pathways that underlie cognition, motivation, and behavior regulation. Future research should consider cannabis use before pregnancy, the timing and route of exposure, polysubstance exposures, and inter-generational effects.

Cannabis and cannabinoid use in autism spectrum disorder: a systematic review

INTRODUCTION

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by persistent deficits in social communication and social interaction, associated with the presence of restricted and repetitive patterns of behavior, interests, or activities. Cannabis has been used to alleviate symptoms associated with ASD.

METHOD

We carried out a systematic review of studies that investigated the clinical effects of cannabis and cannabinoid use on ASD, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA checklist). The search was carried out in four databases: MEDLINE/PubMed, Scientific Electronic Library Online (SciELO), Scopus, and Web of Science. No limits were established for language during the selection process. Nine studies were selected and analyzed.

RESULTS

Some studies showed that cannabis products reduced the number and/or intensity of different symptoms, including hyperactivity, attacks of self-mutilation and anger, sleep problems, anxiety, restlessness, psychomotor agitation, irritability, aggressiveness perseverance, and depression. Moreover, they found an improvement in cognition, sensory sensitivity, attention, social interaction, and language. The most common adverse effects were sleep disorders, restlessness, nervousness and change in appetite.

CONCLUSION

Cannabis and cannabinoids may have promising effects in the treatment of symptoms related to ASD, and can be used as a therapeutic alternative in the relief of those symptoms. However, randomized, blind, placebo-controlled clinical trials are necessary to clarify findings on the effects of cannabis and its cannabinoids in individuals with ASD.

SYSTEMATIC REVIEW REGISTRATION

International Prospective Register of Systematic Reviews (PROSPERO), code 164161.

Update on the developmental consequences of cannabis use during pregnancy and lactation

There is a strong increase in prevalence trends for cannabis use during pregnancy and lactation as more states legalize use of this drug. Information on the teratogenic risk of cannabis is limited but some important themes can be gleaned. Studies have not found a unique phenotypic signature of prenatal exposure but an increased risk of congenital anomalies, particularly gastroschisis, has been reported. Changes in fetal growth have been described in some epidemiological studies but long-term patterns of physical growth appear unaffected. Prenatal exposure to cannabis is not generally associated with reductions in global IQ but specific cognitive skills, especially attention and memory, can be negatively impacted. Long-term impacts on psychological health include increased rates of depressive symptoms and anxiety as well as delinquency. Relatively little is known about the risk of maternal cannabis use during lactation but data suggest that infant exposure is relatively low compared to maternal exposure. As delta-9-tetrahydrocannabinol (THC) levels increase to meet consumer demand and routes of exposure diversify, there is a strong need for prospective birth-cohort studies that collect biological samples to quantify exposure. Data from such studies will be critical to overcoming the weaknesses of past cannabis research and are essential to establishing reliable information on the risks of maternal use. Until that time, health care providers should be encouraged to talk about the risks and benefits associated with cannabis use during pregnancy and lactation with their patients, emphasizing that fetal and neonatal risks cannot be excluded at this time.

Cannabis, Cannabinoids, and Brain Morphology: A Review of the Evidence

Cannabis and cannabinoid-based products are increasingly being accepted and commodified globally. Yet there is currently limited understanding of the effect of the varied cannabinoid compounds on the brain. Exogenous cannabinoids interact with the endogenous cannabinoid system that underpins vital functions in the brain and body, and they are thought to perturb key brain and cognitive function. However, much neuroimaging research has been confined to observational studies of cannabis users, without examining the specific role of the various cannabinoids (Δ⁹-tetrahydrocannabinol, cannabidiol, etc.). This review summarizes the brain structural imaging evidence to date associated with cannabis use, its major cannabinoids (e.g., Δ⁹-tetrahydrocannabinol, cannabidiol), and synthetic cannabinoid products that have emerged as recreational drugs. In doing so, we seek to highlight some of the key issues to consider in understanding cannabinoid-related brain effects, emphasizing the dual neurotoxic and neuroprotective role of cannabinoids, and the need to consider the distinct role of the varied cannabinoids in establishing their effect on the brain.

In utero Δ9-tetrahydrocannabinol exposure confers vulnerability towards cognitive impairments and alcohol drinking in the adolescent offspring: Is there a role for neuropeptide Y?

BACKGROUND

Cannabinoid consumption during pregnancy has been increasing on the wave of the broad-based legalisation of cannabis in Western countries, raising concern about the putative detrimental outcomes on foetal neurodevelopment. Indeed, since the endocannabinoid system regulates synaptic plasticity, emotional and cognitive processes from early stages of life interfering with it and other excitability endogenous modulators, such as neuropeptide Y (NPY), might contribute to the occurrence of a vulnerable phenotype later in life.

AIMS

This research investigated whether in utero exposure to Δ9-tetrahydrocannabinol (THC) may induce deficits in emotional/cognitive processes and alcohol vulnerability in adolescent offspring. NPY and excitatory postsynaptic density (PSD) machinery were measured as markers of neurobiological vulnerability.

METHODS

Following in utero THC exposure (2 mg/kg delivered subcutaneously), preadolescent male rat offspring were assessed for: behavioural reactivity in the open field test, neutral declarative memory and aversive limbic memory in the Novel Object and Emotional Object Recognition tests, immunofluorescence for NPY neurons and the PSD proteins Homer-1, 1b/c and 2 in the prefrontal cortex, amygdala and nucleus accumbens at adolescence (cohort 1); and instrumental learning, alcohol taking, relapse and conflict behaviour in the operant chamber throughout adolescence until early adulthood (cohort 2).

RESULTS

In utero THC-exposed adolescent rats showed: (a) increased locomotor activity; (b) no alteration in neutral declarative memory; (c) impaired aversive limbic memory; (d) decreased NPY-positive neurons in limbic regions; (e) region-specific variations in Homer-1, 1b/c and 2 immunoreactivity; (f) decreased instrumental learning and increased alcohol drinking, relapse and conflict behaviour in the operant chamber.

CONCLUSION

Gestational THC impaired the formation of memory traces when integration between environmental encoding and emotional/motivational processing was required and promoted the development of alcohol-addictive behaviours. The abnormalities in NPY signalling and PSD make-up may represent the common neurobiological background, suggesting new targets for future research.

Sex differences in the interactive effects of early life stress and the endocannabinoid system

Sex differences in both the endocannabinoid system and stress responses have been established for decades. While there is ample evidence that the sexes respond differently to stress and that the endocannabinoid system is involved in this response, what is less clear is whether the endocannabinoid system mediates this response to stress differently in both sexes. Also, do the sexes respond similarly to exogenous cannabinoids (CBs) following stress? Can the administration of exogenous CBs normalize the effects of stress and if so, does this happen similarly in male and female subjects? This review will attempt to delineate the stress induced neurochemical alterations in the endocannabinoid system and the resulting behavioral changes across periods of development: prenatal, early neonatal or adolescent in males and females. Within this frame work, we will then examine the neurochemical and behavioral effects of exogenous CBs and illustrate that the response to CBs is determined by the stress history of the animal. The theoretical framework for this endeavor relates to the established effects of adverse childhood experiences (ACE) in increasing substance abuse, depression and anxiety and the possibility that individuals with high ACE scores may consume cannabinoids to "self-medicate". Overall, we see that while there are instances where exogenous cannabinoids "normalize" the adverse effects produced by early stress, this normalization does not occur in all animal models with any sort of consistency. The most compelling report where CB administration appears to normalize behaviors altered by early stress, shows minimal differences between the sexes (Alteba et al., 2016). This is in stark contrast to the majority of studies on early stress and the endocannabinoid system where both sexes are included and show quite divergent, in fact opposite, effects in males and females. Frequently there is a disconnect between neurochemical changes and behavioral changes and often, exogenous CBs have greater effects in stressed animals compared to non-stressed controls. This report as well as others reviewed here do support the concept that the effects of exogenous CBs are different in individuals experiencing early stress and that these differences are not equal in males and females. However, due to the wide variety of stressors used and the range of ages when the stress is applied, additional careful studies are warranted to fully understand the interactive effects of stress and the endocannabinoid system in males and females. In general, the findings do not support the statement that CB self-administration is an effective treatment for the adverse behavioral effects of early maltreatment in either males or females. Certainly this review should draw the attention of clinicians working with children, adolescents and adults exposed to early trauma and provide some perspective on the dysregulation of the endocannabinoid system in the response to trauma, the complex actions of exogenous CBs based on stress history and the unique effects of these factors in men and women.

Cannabinoid Exposure via Lactation in Rats Disrupts Perinatal Programming of the Gamma-Aminobutyric Acid Trajectory and Select Early-Life Behaviors

BACKGROUND

Cannabis usage is increasing with its widespread legalization. Cannabis use by mothers during lactation transfers active cannabinoids to the developing offspring during this critical period and alters postnatal neurodevelopment. A key neurodevelopmental landmark is the excitatory to inhibitory gamma-aminobutyric acid (GABA) switch caused by reciprocal changes in expression ratios of the K+/Cl- transporters potassium-chloride cotransporter 2 (KCC2) and sodium-potassium-chloride transporter (NKCC1).

METHODS

Rat dams were treated with Δ9-tetrahydrocannabinol or a synthetic cannabinoid during the first 10 days of postnatal development, and experiments were then conducted in the offspring exposed to these drugs via lactation. The network influence of GABA transmission was analyzed using cell-attached recordings. KCC2 and NKCC1 levels were determined using Western blot and quantitative polymerase chain reaction analyses. Ultrasonic vocalization and homing behavioral experiments were carried out at relevant time points.

RESULTS

Treating rat dams with cannabinoids during early lactation retards transcriptional upregulation and expression of KCC2, thereby delaying the GABA switch in pups of both sexes. This perturbed trajectory was corrected by the NKCC1 antagonist bumetanide and accompanied by alterations in ultrasonic vocalization without changes in homing behavior. Neurobehavioral deficits were prevented by CB1 receptor antagonism during maternal exposure, showing that the CB1 receptor underlies the cannabinoid-induced alterations.

CONCLUSIONS

These results reveal how perinatal cannabinoid exposure retards an early milestone of development, delaying the trajectory of GABA's polarity transition and altering early-life communication.

Cannabis use during pregnancy and its relationship with fetal developmental outcomes and psychiatric disorders. A systematic review

INTRODUCTION

This study analyze factors associated to cannabis use in pregnant women, its perceived availability, its risk perception and the relationship between prenatal exposure to cannabis and developmental and mental disorders.

OBJECTIVES

We present a review of the literature on cannabis use among pregnant women. The objective is to analyze factors associated to cannabis use during pregnancy and assess the potential effects of prenatal exposure to cannabis on the development of the fetus and the mental health of those exposed.

METHODS

Systematic review of studies on the maternal use of cannabis and the relationship between early exposure and the development of psychiatric disorders in the PubMed database until July 2018 in English and Spanish with the following keywords: Marijuana, Cannabinoids, Mental disorders, Pregnancy, Prenatal Cannabis Exposure, Risk factors.

RESULTS

The use of cannabis among pregnant women is frequent but it has not been extensively researched. Prenatal exposure to cannabis may be associated with affective symptoms and ADHD.

CONCLUSIONS

Mental healthcare professionals who treat women during their fertile life need to be able to explain the relationship between prenatal exposure to cannabis and the presence of developmental and mental disorders.

Sex-specific behavioural deficits induced at early life by prenatal exposure to the cannabinoid receptor agonist WIN55, 212-2 depend on mGlu5 receptor signalling

BACKGROUND AND PURPOSE

Marijuana is the illicit drug most commonly used among pregnant and breastfeeding women. Different studies reported long-term adverse effects induced by in utero exposure to the main component of marijuana, Δ9 -tetrahydrocannabinol (THC), both in rodents and in humans. However, little is known about any potential sex-dependent effects of marijuana consumption during pregnancy on newborns at early developmental ages.

EXPERIMENTAL APPROACH

We studied the effects of prenatal exposure to the cannabinoid receptor agonist WIN55,212-2 (WIN; 0.5 mg·kg-1 from GD5 to GD20) on the emotional reactivity and cognitive performance of male and female rat offspring from infancy through adolescence and tested the role of mGlu5 receptor signalling in the observed effects.

KEY RESULTS

Prenatally WIN-exposed male infant pups emitted less isolation-induced ultrasonic vocalizations compared with male control pups, when separated from the dam and siblings and showed increased locomotor activity while females were spared. These effects were normalized when male pups were treated with the positive allosteric modulator of mGlu5 receptor CDPPB. When tested at the prepubertal and pubertal periods, WIN-prenatally exposed rats of both sexes did not show any difference in social play behaviour, anxiety and temporal order memory.

CONCLUSIONS AND IMPLICATIONS

We reveal a previously undisclosed sexual divergence in the consequences of fetal cannabinoids on newborns at early developmental ages, which is dependent on mGlu5 receptor signalling. These results provide new impetus for the urgent need to investigate the functional and behavioural substrates of prenatal cannabinoid exposure in both the male offspring and the female offspring.

Consequences of Perinatal Cannabis Exposure

Cannabis exposure during the perinatal period results in varied and significant consequences in affected offspring. The prevalence of detrimental outcomes of perinatal cannabis exposure is likely to increase in tandem with the broadening of legalization and acceptance of the drug. As such, it is crucial to highlight the immediate and protracted consequences of cannabis exposure on pre- and postnatal development. Here, we identify lasting changes in neurons' learning flexibility (synaptic plasticity) and epigenetic misregulation in animal models of perinatal cannabinoid exposure (using synthetic cannabinoids or active components of the cannabis plant), in addition to significant alterations in social behavior and executive functions. These findings are supported by epidemiological data indicating similar behavioral outcomes throughout life in human offspring exposed to cannabis during pregnancy. Further, we indicate important lingering questions regarding accurate modeling of perinatal cannabis exposure as well as the need for sex- and age-dependent outcome measures in future studies.

Altered motor development following late gestational alcohol and cannabinoid exposure in rats

Cannabis is the most commonly used illicit drug among pregnant women, and rates are likely to increase given recent legalization. In addition, half of pregnant women who report consuming cannabis also report drinking alcohol. However, little is known about the consequences of prenatal cannabis alone or in combination with alcohol, particularly with cannabis products that are continually increasing in potency of the primary psychoactive constituent in cannabis, Δ9-tetrahydrocannabinol (THC). The current study investigated the effects of early exposure to cannabinoids during the brain growth spurt on early physical and motor development alone (Experiment 1) or in combination with alcohol (Experiment 2). In Experiment 1, Sprague-Dawley rat pups were exposed to a cannabinoid receptor agonist (CP-55,940 [CP]; 0.1, 0.25, 0.4 mg/kg/day), the drug vehicle, or a saline control from postnatal days (PD) 4-9. In Experiment 2, rat pups were exposed to CP (0.4 mg/kg/day) or the vehicle, and were additionally intubated with alcohol (11.9% v/v; 5.25 g/kg/day) or received a sham intubation. Subjects in both experiments were tested on a motor development task (PD 12-20) and a motor coordination task during adolescence (PD 30-32). Both developmental cannabinoid and alcohol exposure separately decreased body growth throughout development, and combined exposure exacerbated these effects, although only alcohol exposure induced long-term body weight reductions. Developmental cannabinoid exposure advanced early motor development, whereas alcohol exposure delayed development, and subjects given combined exposure did not differ from controls on some measures. Alcohol exposure impaired motor coordination later in life. In contrast, cannabinoid exposure, by itself, did not significantly affect long-term motor coordination, but did exacerbate alcohol-related impairments in motor coordination among females. These results suggest that cannabinoid exposure may not only alter development by itself, but may exacerbate alcohol's teratogenic effects in specific behavioral domains. These findings have important implications not only for individuals affected by prenatal exposure, but also for establishing public policy for women regarding cannabis use during pregnancy.

The effects of alcohol and cannabinoid exposure during the brain growth spurt on behavioral development in rats

Cannabis is the most commonly used illicit drug among pregnant women. Moreover, over half of pregnant women who are consuming cannabis are also consuming alcohol; however, the consequences of combined prenatal alcohol and cannabis exposure on fetal development are not well understood. The current study examined behavioral development following exposure to ethanol (EtOH) and/or CP-55,940 (CP), a cannabinoid receptor agonist. From postnatal days (PD) 4-9, a period of brain development equivalent to the third trimester, Sprague-Dawley rats received EtOH (5.25 g/kg/day) or sham intubation, as well as CP (0.4 mg/kg/day) or vehicle. All subjects were tested on open field activity (PD 18-21), elevated plus maze (PD 25), and spatial learning (PD 40-46) tasks. Both EtOH and CP increased locomotor activity in the open field, and the combination produced more severe overactivity than either exposure alone. Similarly, increases in thigmotaxis in the Morris water maze were caused by either EtOH or CP alone, and were more severe with combined exposure, although only EtOH impaired spatial learning. Finally, developmental CP significantly increased time spent in the open arms on the elevated plus maze. Overall, these data indicate that EtOH and CP produce some independent effects on behavior, and that the combination produces more severe overactivity in the open field. Importantly, these data suggest that prenatal cannabis disrupts development and combined prenatal exposure to alcohol and cannabis may be particularly damaging to the developing fetus, which has implications for the lives of affected individuals and families and also for establishing public health policy.

Longitudinal Alterations in Prefrontal Resting Brain Connectivity in Non-Treatment-Seeking Young Adults With Cannabis Use Disorder

Background: Cannabis is increasingly perceived as a harmless drug by recreational users, yet chronic use may impact brain changes into adulthood. Repeated cannabis exposure has been associated with enduring synaptic changes in executive control and reward networks. It is important to determine whether there are brain functional alterations within these networks in individuals that do not seek treatment for chronic cannabis abuse. Methods: This longitudinal study compared resting-state functional connectivity changes in executive control and reward networks between 23 non-treatment-seeking young adults with cannabis use disorder (6 females; baseline age M = 19.3 ± 1.18) and 21 age-matched controls (10 females; baseline age M = 19.4 ± 0.65) to determine group differences in the temporal trajectories of resting-state functional connectivity across a 2-year span. Results: Results showed i) significant increases in resting-state functional connectivity between the caudal anterior cingulate cortex and precentral and parietal regions over time in the control group, but not in the cannabis use disorder group, and ii) sustained lower resting-state functional connectivity of anterior cingulate cortex seeds with frontal and thalamic regions in the cannabis use disorder group vs. the age-matched controls. Resting-state functional connectivity strength was correlated with cannabis use patterns in the cannabis use disorder sample. Conclusion: Longitudinal alterations in intrinsic functional organization of executive control networks found in non-treatment-seeking young adults with cannabis use disorder (when compared to age-matched controls) may impact regulatory control over substance use behavior. Current findings were limited to examining executive control and reward networks seeded in ACC and NAcc, respectively. Future studies with larger sample sizes and enough power are needed to conduct exploratory analyses examining rsFC of other networks beyond those within the scope of the current study.

Physiology of the Endocannabinoid System During Development

The endocannabinoid (eCB) system comprises endogenously produced cannabinoids (CBs), enzymes of their production and degradation, and CB-sensing receptors and transporters. The eCB system plays a critical role in virtually all stages of animal development. Studies on eCB system components and their physiological role have gained increasing attention with the rising legalization and medical use of marijuana products. The latter represent exogenous interventions that target the eCB system. This chapter summarizes knowledge in the field of CB contribution to gametogenesis, fertilization, embryo implantation, fetal development, birth, and adolescence-equivalent periods of ontogenesis. The material is complemented by the overview of data from our laboratory documenting the functional presence of the eCB system within cerebral arteries of baboons at different stages of development.

The Endocannabinoid System and Cannabidiol's Promise for the Treatment of Substance Use Disorder

Substance use disorder is characterized by repeated use of a substance, leading to clinically significant distress, making it a serious public health concern. The endocannabinoid system plays an important role in common neurobiological processes underlying substance use disorder, in particular by mediating the rewarding and motivational effects of substances and substance-related cues. In turn, a number of cannabinoid drugs (e.g., rimonabant, nabiximols) have been suggested for potential pharmacological treatment for substance dependence. Recently, cannabidiol (CBD), a non-psychoactive phytocannabinoid found in the cannabis plant, has also been proposed as a potentially effective treatment for the management of substance use disorder. Animal and human studies suggest that these cannabinoids have the potential to reduce craving and relapse in abstinent substance users, by impairing reconsolidation of drug-reward memory, salience of drug cues, and inhibiting the reward-facilitating effect of drugs. Such functions likely arise through the targeting of the endocannabinoid and serotonergic systems, although the exact mechanism is yet to be elucidated. This article seeks to review the role of the endocannabinoid system in substance use disorder and the proposed pharmacological action supporting cannabinoid drugs' therapeutic potential in addictions, with a focus on CBD. Subsequently, this article will evaluate the underlying evidence for CBD as a potential treatment for substance use disorder, across a range of substances including nicotine, alcohol, psychostimulants, opioids, and cannabis. While early research supports CBD's promise, further investigation and validation of CBD's efficacy, across preclinical and clinical trials will be necessary.

Prenatal influences on temperament development: The role of environmental epigenetics

This review summarizes current knowledge and outlines future directions relevant to questions concerning environmental epigenetics and the processes that contribute to temperament development. Links between prenatal adversity, epigenetic programming, and early manifestations of temperament are important in their own right, also informing our understanding of biological foundations for social-emotional development. In addition, infant temperament attributes represent key etiological factors in the onset of developmental psychopathology, and studies elucidating their prenatal foundations expand our understanding of developmental origins of health and disease. Prenatal adversity can take many forms, and this overview is focused on the environmental effects of stress, toxicants, substance use/psychotropic medication, and nutrition. Dysregulation associated with attention-deficit/hyperactivity-disruptive disorders was noted in the context of maternal substance use and toxicant exposures during gestation, as well as stress. Although these links can be made based on the existing literature, currently few studies directly connect environmental influences, epigenetic programming, and changes in brain development/behavior. The chain of events starting with environmental inputs and resulting in alterations to gene expression, physiology, and behavior of the organism is driven by epigenetics. Epigenetics provides the molecular mechanism of how environmental factors impact development and subsequent health and disease, including early brain and temperament development.

Pregnant Women's Current and Intended Cannabis Use in Relation to Their Views Toward Legalization and Knowledge of Potential Harm

OBJECTIVES

The objective of this study was to investigate pregnant women's current use of cannabis and their intended patterns of use with relation to their views on the legalization of cannabis and their knowledge of potential harms.

METHODS

A voluntary, anonymous survey regarding patterns of use of cannabis and views on legalization was distributed to a convenience sample of pregnant women presenting for prenatal care at an outpatient university clinic. Chi-square and Fischer's exact tests were used for analysis using STATA.

RESULTS

Of 306 surveys returned, 35% of women reported currently using cannabis at the time of diagnosis of pregnancy and 34% of those women continued to use. Seventy percent of respondents endorsed the belief that cannabis could be harmful to a pregnancy. Fifty-nine percent of respondents believed that cannabis should be legalized in some form and 10% reported that they would use cannabis more during pregnancy if it were legalized. Those who continued to use cannabis during pregnancy were less likely than those who quit to believe that cannabis use could be harmful during pregnancy (26% vs 75%, P < 0.001). The most common motivation for quitting cannabis use in pregnancy was to avoid being a bad example (74%); in comparison, only 27% of respondents listed a doctor's recommendation as a motivation to quit.

CONCLUSIONS

Cannabis use during pregnancy is relatively common and persistent, despite knowledge of the potential risks of harm. Views toward legalization vary among pregnant women and may impact cannabis use during pregnancy. In a changing legal climate, there is a need for clear messaging on the effects of cannabis use during pregnancy.

Cannabis use during pregnancy: Pharmacokinetics and effects on child development

The broad-based legalization of cannabis use has created a strong need to understand its impact on human health and behavior. The risks that may be associated with cannabis use, particularly for sensitive subgroups such as pregnant women, are difficult to define because of a paucity of dose-response data and the recent increase in cannabis potency. Although there is a large body of evidence detailing the mode of action of Δ⁹-tetrahydrocannabinol (THC) in adults, little work has focused on understanding how cannabis use during pregnancy may impact the development of the fetal nervous system and whether additional plant-derived cannabinoids might participate. This manuscript presents an overview of the historical and contemporary literature focused on the mode of action of THC in the developing brain, comparative pharmacokinetics in both pregnant and nonpregnant model systems and neurodevelopmental outcomes in exposed offspring. Despite growing public health significance, pharmacokinetic studies of THC have focused on nonpregnant adult subjects and there are few published reports on disposition parameters during pregnancy. Data from preclinical species show that THC readily crosses the placenta although fetal exposures appear lower than maternal exposures. The neurodevelopmental data in humans and animals suggest that prenatal exposure to THC may lead to subtle, persistent changes in targeted aspects of higher-level cognition and psychological well-being. There is an urgent need for well-controlled studies in humans and preclinical models on THC as a developmental neurotoxicant. Until more information is available, pregnant women should not assume that using cannabis during pregnancy is safe.

Targeting anandamide metabolism rescues core and associated autistic-like symptoms in rats prenatally exposed to valproic acid

Autism spectrum disorders (ASD) are characterized by altered sociability, compromised communication and stereotyped/repetitive behaviors, for which no specific treatments are currently available. Prenatal exposure to valproic acid (VPA) is a known, although still underestimated, environmental risk factor for ASD. Altered endocannabinoid activity has been observed in autistic patients, and endocannabinoids are known to modulate behavioral traits that are typically affected in ASD. On this basis, we tested the hypothesis that changes in the endocannabinoid tone contribute to the altered phenotype induced by prenatal VPA exposure in rats, with focus on behavioral features that resemble the core and associated symptoms of ASD. In the course of development, VPA-exposed rats showed early deficits in social communication and discrimination, compromised sociability and social play behavior, stereotypies and increased anxiety, thus providing preclinical proof of the long-lasting deleterious effects induced by prenatal VPA exposure. At the neurochemical level, VPA-exposed rats displayed altered phosphorylation of CB1 cannabinoid receptors in different brain areas, associated with changes in anandamide metabolism from infancy to adulthood. Interestingly, enhancing anandamide signaling through inhibition of its degradation rescued the behavioral deficits displayed by VPA-exposed rats at infancy, adolescence and adulthood. This study therefore shows that abnormalities in anandamide activity may underlie the deleterious impact of environmental risk factors on ASD-relevant behaviors and that the endocannabinoid system may represent a therapeutic target for the core and associated symptoms displayed by autistic patients.

Prenatal cannabis exposure - The "first hit" to the endocannabinoid system

As more states and countries legalize medical and/or adult recreational marijuana use, the incidences of prenatal cannabis exposure (PCE) will likely increase. While young people increasingly view marijuana as innocuous, marijuana preparations have been growing in potency in recent years, potentially creating global clinical, public health, and workforce concerns. Unlike fetal alcohol spectrum disorder, there is no phenotypic syndrome associated with PCE. There is also no preponderance of evidence that PCE causes lifelong cognitive, behavioral, or functional abnormalities, and/or susceptibility to subsequent addiction. However, there is compelling circumstantial evidence, based on the principles of teratology and fetal malprogramming, suggesting that pregnant women should refrain from smoking marijuana. The usage of marijuana during pregnancy perturbs the fetal endogenous cannabinoid signaling system (ECSS), which is present and active from the early embryonic stage, modulating neurodevelopment and continuing this role into adulthood. The ECSS is present in virtually every brain structure and organ system, and there is also evidence that this system is important in the regulation of cardiovascular processes. Endocannabinoids (eCBs) undergird a broad spectrum of processes, including the early stages of fetal neurodevelopment and uterine implantation. Delta-9-tetrahydrocannabinol (THC), the psychoactive chemical in cannabis, enters maternal circulation, and readily crosses the placental membrane. THC binds to CB receptors of the fetal ECSS, altering neurodevelopment and possibly rewiring ECSS circuitry. In this review, we discuss the Double-Hit Hypothesis as it relates to PCE. We contend that PCE, similar to a neurodevelopmental teratogen, delivers the first hit to the ECSS, which is compromised in such a way that a second hit (i.e., postnatal stressors) will precipitate the emergence of a specific phenotype. In summary, we conclude that perturbations of the intrauterine milieu via the introduction of exogenous CBs alter the fetal ECSS, predisposing the offspring to abnormalities in cognition and altered emotionality. Based on recent experimental evidence that we will review here, we argue that young women who become pregnant should immediately take a "pregnant pause" from using marijuana.

Striatal but not frontal cortical up-regulation of the epidermal growth factor receptor in rats exposed to immune activation in utero and cannabinoid treatment in adolescence

In utero maternal immune activation (MIA) and cannabinoid exposure during adolescence constitute environmental risk factors for schizophrenia. We investigated these risk factors alone and in combination ("two-hit") on epidermal growth factor receptor (EGFR) and neuregulin-1 receptor (ErbB4) levels in the rat brain. EGFR but not ErbB4 receptor protein levels were significantly increased in the nucleus accumbens and striatum of "two-hit" rats only, with no changes seen at the mRNA level. These findings support region specific EGF-system dysregulation as a plausible mechanism in this animal model of schizophrenia pathogenesis.

MicroRNA: Small RNA mediators of the brains genomic response to environmental stress

The developmental processes that establish the synaptic architecture of the brain while retaining capacity for activity-dependent remodeling, are complex and involve a combination of genetic and epigenetic influences. Dysregulation of these processes can lead to problems with neural circuitry which manifest in humans as a range of neurodevelopmental syndromes, such as schizophrenia, bipolar disorder and fragile X mental retardation. Recent studies suggest that prenatal, postnatal and intergenerational environmental factors play an important role in the aetiology of stress-related psychopathology. A number of these disorders have been shown to display epigenetic changes in the postmortem brain that reflect early life experience. These changes affect the regulation of gene expression though chromatin remodeling (transcriptional) and post-transcriptional influences, especially small noncoding microRNA (miRNA). These dynamic and influential molecules appear to play an important function in both brain development and its adaption to stress. In this review, we examine the role of miRNA in mediating the brain's response to both prenatal and postnatal environmental perturbations and explore how stress- induced alterations in miRNA expression can regulate the stress response via modulation of the immune system. Given the close relationship between environmental stress, miRNA, and brain development/function, we assert that miRNA hold a significant position at the molecular crossroads between neural development and adaptations to environmental stress. A greater understanding of the dynamics that mediate an individual's predisposition to stress-induced neuropathology has major human health benefits and is an important area of research.

Behavioral effects of D3 receptor inhibition and 5-HT4 receptor activation on animals undergoing chronic cannabinoid exposure during adolescence

Chronic exposure to cannabinoids during adolescence results in long-lasting behavioral deficits that match some symptomatologic aspects of schizophrenia. The aim of this study was to investigate the reversibility of the emotional and the cognitive effects of chronic exposure to cannabinoids during adolescence, via subsequent modulation of the serotoninergic 5-HT4 and dopaminergic D3 receptors. RS67333 as a 5-HT4 agonist and U-99194A as a D3 antagonist were administered separately at 1 mg/kg and 20 mg/kg, and in combination at 0.5 mg/kg and 10 mg/kg to adult animals undergoing chronic treatment with the synthetic cannabinoid receptor agonist WIN55,212-2 (1 mg/kg) during adolescence. Animals were tested for anxiety-like behavior and episodic-like memory in the open field and novel object recognition tests respectively 30 minutes after the last drug administration. Chronic WIN55,212-2 treated animals exhibited a lasting disruption of episodic memory and increased anxiety levels. The effect on episodic-like memory were partially restored by acute administration of RS67333 and U-99194A and completely by administration of both drugs in combination at lower doses. However, only RS67333 (20 mg/kg) improved the anxiogenic-like effect of WIN55,212-2. These findings give further support that chronic exposure to cannabinoids during adolescence may be used as an animal model for schizophrenia, and highlight D3 and 5-HT4 receptors as potential targets for an enhanced treatment of the cognitive aspect of this disease.

The Medicinal Cannabis Treatment Agreement: Providing Information to Chronic Pain Patients Through a Written Document

AIM

Pain practitioners would seem to have an obligation to understand and inform their patients on key issues of the evidence base on cannabinoid therapeutics. One way to fulfill this obligation might be to borrow from concepts developed in the prescription of opioids: the use of a written agreement to describe and minimize risks. Regrettably, the widespread adoption of opioids was undertaken while harmful effects were minimized; obviously, no one wants to repeat this misstep.

OBJECTIVE

This article describes a method of educating patients in a manner analogous to other treatment agreements.

BACKGROUND

Surveys have demonstrated that pain is the most common indication for medical use of cannabis. As more individuals gain access to this botanical product through state ballot initiatives and legislative mandate, the pain specialist is likely to be confronted by patients either seeking such treatment where permitted, or otherwise inquiring about its potential benefits and harms, and alternative pharmaceuticals containing cannabinoids.

METHODS

PubMed searches were conducted using the following keywords: cannabis guidelines, harmful effects of cannabis, medical marijuana, medicinal cannabis, opioid cannabis interaction, cannabis dependence and cannabis abuse

RESULTS

: The authors selected individual tenets a medicinal cannabis patient would be asked to review and acknowledge via signature.

CONCLUSIONS

Undoubtedly, the knowledge base concerning risks will be an iterative process as we learn more about the long-term use of medicinal cannabis. But we should start the process now so that patients may be instructed about our current conception of what the use of medicinal cannabis entails.

Distinct roles of the endocannabinoids anandamide and 2-arachidonoylglycerol in social behavior and emotionality at different developmental ages in rats

To date, our understanding of the relative contribution and potential overlapping roles of the endocannabinoids anandamide (AEA) and 2-arachidonoylglycerol (2-AG) in the regulation of brain function and behavior is still limited. To address this issue, we investigated the effects of systemic administration of JZL195, that simultaneously increases AEA and 2-AG signaling by inhibiting their hydrolysis, in the regulation of socio-emotional behavior in adolescent and adult rats. JZL195, administered at the dose of 0.01mg/kg, increased social play behavior, that is the most characteristic social activity displayed by adolescent rats, and increased social interaction in adult animals. At both ages, these behavioral effects were antagonized by the CB1 cannabinoid receptor antagonist SR141716A and were associated with increased brain levels of 2-AG, but not AEA. Conversely, at the dose of 1mg/kg, JZL195 decreased general social exploration in adolescent rats without affecting social play behavior, and induced anxiogenic-like effects in the elevated plus-maze test both in adolescent and adult animals. These effects, mediated by activation of CB1 cannabinoid receptors, were paralleled by simultaneous increase in AEA and 2-AG levels in adolescent rats, and by an increase of only 2-AG levels in adult animals. These findings provide the first evidence for a role of 2-AG in social behavior, highlight the different contributions of AEA and 2-AG in the modulation of emotionality at different developmental ages and suggest that pharmacological inhibition of AEA and 2-AG hydrolysis is a useful approach to investigate the role of these endocannabinoids in neurobehavioral processes.

The influence of cannabinoids on learning and memory processes of the dorsal striatum

Extensive evidence indicates that the mammalian endocannabinoid system plays an integral role in learning and memory. Our understanding of how cannabinoids influence memory comes predominantly from studies examining cognitive and emotional memory systems mediated by the hippocampus and amygdala, respectively. However, recent evidence suggests that cannabinoids also affect habit or stimulus-response (S-R) memory mediated by the dorsal striatum. Studies implementing a variety of maze tasks in rats indicate that systemic or intra-dorsolateral striatum infusions of cannabinoid receptor agonists or antagonists impair habit memory. In mice, cannabinoid 1 (CB1) receptor knockdown can enhance or impair habit formation, whereas Δ(9)THC tolerance enhances habit formation. Studies in human cannabis users also suggest an enhancement of S-R/habit memory. A tentative conclusion based on the available data is that acute disruption of the endocannabinoid system with either agonists or antagonists impairs, whereas chronic cannabinoid exposure enhances, dorsal striatum-dependent S-R/habit memory. CB1 receptors are required for multiple forms of striatal synaptic plasticity implicated in memory, including short-term and long-term depression. Interactions with the hippocampus-dependent memory system may also have a role in some of the observed effects of cannabinoids on habit memory. The impairing effect often observed with acute cannabinoid administration argues for cannabinoid-based treatments for human psychopathologies associated with a dysfunctional habit memory system (e.g. post-traumatic stress disorder and drug addiction/relapse). In addition, the enhancing effect of repeated cannabinoid exposure on habit memory suggests a novel neurobehavioral mechanism for marijuana addiction involving the dorsal striatum-dependent memory system.

Long-term consequences of perinatal and adolescent cannabinoid exposure on neural and psychological processes

Marihuana is the most widely consumed illicit drug, even among adolescents and pregnant women. Given the critical developmental processes that occur in the adolescent and fetal nervous system, marihuana consumption during these stages may have permanent consequences on several brain functions in later adult life. Here, we review what is currently known about the long-term consequences of perinatal and adolescent cannabinoid exposure. The most consistent findings point to long-term impairments in cognitive function that are associated with structural alterations and disturbed synaptic plasticity. In addition, several neurochemical modifications are also evident after prenatal or adolescent cannabinoid exposure, especially in the endocannabinoid, glutamatergic, dopaminergic and opioidergic systems. Important sexual dimorphisms are also evident in terms of the long-lasting effects of cannabinoid consumption during pregnancy and adolescence, and cannabinoids possibly have a protective effect in adolescents who have suffered traumatic life challenges, such as maternal separation or intense stress. Finally, we suggest some future research directions that may encourage further advances in this exciting field.

Neuronal substrates and functional consequences of prenatal cannabis exposure

Cannabis remains one of the world's most widely used substance of abuse amongst pregnant women. Trends of the last 50 years show an increase in popularity in child-bearing women together with a constant increase in cannabis potency. In addition, potent herbal "legal" highs containing synthetic cannabinoids that mimic the effects of cannabis with unknown pharmacological and toxicological effects have gained rapid popularity amongst young adults. Despite the surge in cannabis use during pregnancy, little is known about the neurobiological and psychological consequences in the exposed offspring. In this review, we emphasize the importance of maternal programming, defined as the intrauterine presentation of maternal stimuli to the foetus, in neurodevelopment. In particular, we focus on cannabis-mediated maternal adverse effects, resulting in direct central nervous system alteration or sensitization to late-onset chronic and neuropsychiatric disorders. We compare clinical and preclinical experimental studies on the effects of foetal cannabis exposure until early adulthood, to stress the importance of animal models that permit the fine control of environmental variables and allow the dissection of cannabis-mediated molecular cascades in the developing central nervous system. In sum, we conclude that preclinical experimental models confirm clinical studies and that cannabis exposure evokes significant molecular modifications to neurodevelopmental programs leading to neurophysiological and behavioural abnormalities.

Alteration of imprinted Dlk1-Dio3 miRNA cluster expression in the entorhinal cortex induced by maternal immune activation and adolescent cannabinoid exposure

A significant feature of the cortical neuropathology of schizophrenia is a disturbance in the biogenesis of short non-coding microRNA (miRNA) that regulate translation and stability of mRNA. While the biological origin of this phenomenon has not been defined, it is plausible that it relates to major environmental risk factors associated with the disorder such as exposure to maternal immune activation (MIA) and adolescent cannabis use. To explore this hypothesis, we administered the viral mimic poly I:C to pregnant rats and further exposed some of their maturing offsprings to daily injections of the synthetic cannabinoid HU210 for 14 days starting on postnatal day 35. Whole-genome miRNA expression analysis was then performed on the left and right hemispheres of the entorhinal cortex (EC), a region strongly associated with schizophrenia. Animals exposed to either treatment alone or in combination exhibited significant differences in the expression of miRNA in the left hemisphere, whereas the right hemisphere was less responsive. Hemisphere-associated differences in miRNA expression were greatest in the combined treatment and highly over-represented in a single imprinted locus on chromosome 6q32. This observation was significant as the syntenic 14q32 locus in humans encodes a large proportion of miRNAs differentially expressed in peripheral blood lymphocytes from patients with schizophrenia, suggesting that interaction of early and late environmental insults may affect miRNA expression, in a manner that is relevant to schizophrenia.

Strain- and context-dependent effects of the anandamide hydrolysis inhibitor URB597 on social behavior in rats

Genetic and environmental factors play an important role in the cannabinoid modulation of motivation and emotion. Therefore, the aim of the present study was to test whether anandamide modulation of social behavior is strain- and context-dependent. We tested the effects of the anandamide hydrolysis inhibitor URB597 on social behavior and 50-kHz ultrasonic vocalizations (USVs) in adolescent and adult Wistar and Sprague-Dawley rats tested in different emotionally arousing conditions (familiarity/unfamiliarity to the test cage, low/high light). Under all experimental conditions, adolescent and adult Sprague-Dawley rats displayed higher levels of social behavior and emitted more 50-kHz USVs than Wistar rats. URB597 enhanced social play behavior in adolescent Wistar rats under all experimental conditions. However, URB597 only increased social interaction in adult Wistar rats under unfamiliar/high light conditions. URB597 did not affect adolescent social play behavior and adult social interaction in Sprague-Dawley rats under any experimental condition. Moreover, URB597 increased the USVs emitted during social interaction by adolescent Wistar and adult Sprague-Dawley rats tested under familiar/high light and unfamiliar/high light, respectively. These results show that anandamide has distinct roles in adolescent and adult social behaviors. Anandamide modulation of adolescent social play behavior is strain- but not context-dependent. Conversely, anandamide modulation of adult social behavior and USV emission depends upon both strain and experimental context. Furthermore, these results confirm that profound behavioral differences exist between Wistar and Sprague-Dawley rats, which may explain the sometimes contradictory effects of cannabinoid drugs on emotionality in different strains of rodents.

Prenatal cannabis exposure and infant outcomes: overview of studies

Accumulating evidence from both human and preclinical studies indicates maternal substance use during pregnancy can affect fetal development, birth weight and infant outcomes. Thus, the prenatal period can be regarded as an important and potentially sensitive period of development. In this manuscript, an updated overview of studies on prenatal cannabis exposure in humans is presented, including recent studies conducted within the Generation R study. Findings on fetal growth, birth outcomes, early neonatal behavior and infant behavior and cognitive development are discussed in detail. Preclinical evidence and potential mechanisms are described as well, and recommendations for future studies are provided. It is concluded that evidence seems to suggest that fetal development is affected by prenatal maternal cannabis use, while findings on effects on infant behavior or cognition are inconsistent. Beyond infancy, subtle differences may be found in specific cognitive or behavioral outcomes, although replication studies in which pregnant women and their fetuses are exposed to current and probably higher levels of Δ9-tetrahydrocannabinol and novel designs are needed to come to firm conclusions.

The endocannabinoid system: an emotional buffer in the modulation of memory function

Extensive evidence indicates that endocannabinoids modulate cognitive processes in animal models and human subjects. However, the results of endocannabinoid system manipulations on cognition have been contradictory. As for anxiety behavior, a duality has indeed emerged with regard to cannabinoid effects on memory for emotional experiences. Here we summarize findings describing cannabinoid effects on memory acquisition, consolidation, retrieval and extinction. Additionally, we review findings showing how the endocannabinoid system modulates memory function differentially, depending on the level of stress and arousal associated with the experimental context. Based on the evidence reviewed here, we propose that the endocannabinoid system is an emotional buffer that moderates the effects of environmental context and stress on cognitive processes.

The endocannabinoid transport inhibitor AM404 differentially modulates recognition memory in rats depending on environmental aversiveness

Cannabinoid compounds may influence both emotional and cognitive processes depending on the level of environmental aversiveness at the time of drug administration. However, the mechanisms responsible for these responses remain to be elucidated. The present experiments investigated the effects induced by the endocannabinoid transport inhibitor AM404 (0.5-5 mg/kg, i.p.) on both emotional and cognitive performances of rats tested in a Spatial Open Field task and subjected to different experimental settings, named High Arousal (HA) and Low Arousal (LA) conditions. The two different experimental conditions influenced emotional reactivity independently of drug administration. Indeed, vehicle-treated rats exposed to the LA condition spent more time in the center of the arena than vehicle-treated rats exposed to the HA context. Conversely, the different arousal conditions did not affect the cognitive performances of vehicle-treated animals such as the capability to discriminate a spatial displacement of the objects or an object substitution. AM404 administration did not alter locomotor activity or emotional behavior of animals exposed to both environmental conditions. Interestingly, AM404 administration influenced the cognitive parameters depending on the level of emotional arousal: it impaired the capability of rats exposed to the HA condition to recognize a novel object while it did not induce any impairing effect in rats exposed to the LA condition. These findings suggest that drugs enhancing endocannabinoid signaling induce different effects on recognition memory performance depending on the level of emotional arousal induced by the environmental conditions.