Mesolimbic dopamine dysregulation as a signature of information processing deficits imposed by prenatal THC exposure

Expanding the therapeutic potential of neuro(active)steroids: a promising strategy for hyperdopaminergic behavioral phenotypes

Imbalances in dopamine activity significantly contribute to the pathophysiology of several neuropsychiatric disorders, including addiction, ADHD, schizophrenia, impulse control disorders, and Parkinson's Disease. Neuro(active)steroids, comprising endogenous steroids that finely modulate neuronal activity, are considered crucial regulators of brain function and behavior, with implications in various physiological processes and pathological conditions. Specifically, subclasses of Neuro(active)steroids belonging to the 5α reductase pathway are prominently involved in brain disorders characterized by dopaminergic signaling imbalances. This review highlights the neuromodulatory effects of Neuro(active)steroids on the dopamine system and related aberrant behavioral phenotypes. We critically appraise the role of pregnenolone, progesterone, and allopregnanolone on dopamine signaling. Additionally, we discuss the impact of pharmacological interventions targeting 5α reductase activity in neuropsychiatric conditions characterized by excessive activation of the dopaminergic system, ranging from psychotic (endo)phenotypes and motor complications to decision-making problems and addiction.

Psychotomimetic compensation versus sensitization

It is a paradox that psychotomimetic drugs can relieve symptoms that increase risk of and cooccur with psychosis, such as attention and motivational deficits (e.g., amphetamines), pain (e.g., cannabis) and symptoms of depression (e.g., psychedelics, dissociatives). We introduce the ideas of psychotomimetic compensation and psychotomimetic sensitization to explain this paradox. Psychotomimetic compensation refers to a short-term stressor or drug-induced compensation against stress that is facilitated by engagement of neurotransmitter/modulator systems (endocannabinoid, serotonergic, glutamatergic and dopaminergic) that mediate the effects of common psychotomimetic drugs. Psychotomimetic sensitization occurs after repeated exposure to stress and/or drugs and is evidenced by the gradual intensification and increase of psychotic-like experiences over time. Theoretical and practical implications of this model are discussed.

Fetal Cannabinoid Syndrome: Behavioral and Brain Alterations of the Offspring Exposed to Dronabinol during Gestation and Lactation

This study establishes a fetal cannabinoid syndrome model to evaluate the effects of high doses of dronabinol (synthetic THC) during pregnancy and lactation on behavioral and brain changes in male and female progeny and their susceptibility to alcohol consumption. Female C57BL/6J mice received dronabinol (10 mg/kg/12 h, p.o.) from gestational day 5 to postnatal day 21. On the weaning day, the offspring were separated by sex, and on postnatal day 60, behavioral and neurobiological changes were analyzed. Mice exposed to dronabinol exhibited increased anxiogenic and depressive-like behaviors and cognitive impairment. These behaviors were associated with neurodevelopment-related gene and protein expression changes, establishing, for the first time, an association among behavioral changes, cognitive impairment, and neurobiological alterations. Exposure to dronabinol during pregnancy and lactation disrupted the reward system, leading to increased motivation to consume alcohol in the offspring. All these modifications exhibited sex-dependent patterns. These findings reveal the pronounced adverse effects on fetal neurodevelopment resulting from cannabis use during pregnancy and lactation and strongly suggest the need to prevent mothers who use cannabis in this period from the severe and permanent side effects on behavior and brain development that may occur in their children.

Oral pre- and early postnatal cannabis exposure disinhibits ventral tegmental area dopamine neuron activity but does not influence cocaine preference in offspring in mice

Cannabis consumption has increased from 1.5% to 2.5% in Canada between 2012 and 2019. Clinical studies have indicated effects of prenatal cannabis exposure on birth weight, substance use, and neurodevelopmental disorders, but are confounded by several difficult to control variables. Animal models allow for examination of the mechanism of cannabis-induced changes in neurodevelopment and behavior, while controlling dose and timing. Several animal models of prenatal cannabis exposure exist which provide varying levels of construct validity, control of dose, and exposure to maternal stress. Using a voluntary oral consumption model, mouse dams received 5 mg/kg Δ9-tetrahydrocannabinol (THC) whole cannabis oil in peanut butter daily from gestational day 1 (GD1) to postnatal day 10 (PD10). At GD1, GD18, PD1, PD10, and PD15, maternal plasma was collected; pup brains were collected from GD18 onward. Pup brains had higher levels of THC and cannabidiol at each time point, each of which persisted in maternal plasma and pup brains past the end of treatment (PD15). Male and female adolescent offspring were examined for changes to ventral tegmental area (VTA) dopamine neuron activity and cocaine-seeking behavior. Prenatal and early postnatal (GD1-PD10) cannabis-exposed male, but not female mice had decreased gamma-aminobutyric acid (GABAergic) input, depolarized resting membrane potential, and increased spontaneous firing of VTA dopamine neurons. Cannabis-exposed offspring showed faster decay of N-methyl-D-aspartate (NMDA) currents in both sexes. However, no differences in cocaine-seeking behavior were noted. These data characterize a voluntary prenatal cannabis exposure model and demonstrates VTA dopamine neuronal activity is disinhibited in offspring.

Dynamic Overrepresentation of Accumbal Cues in Food- and Opioid-Seeking Rats after Prenatal THC Exposure

The increasing prevalence of cannabis use during pregnancy has raised significant medical concerns, primarily related to the presence of Δ9-tetrahydrocannabinol (THC), which readily crosses the placenta and impacts fetal brain development. Previous research has identified midbrain dopaminergic neuronal alterations related to maternal THC consumption. However, the enduring consequences that prenatal cannabis exposure (PCE) has on striatum-based processing during voluntary reward pursuit have not been specifically determined. Here, we characterize PCE rats during food (palatable pellets) or opioid (remifentanyl)-maintained reward seeking. We find that the supra motivational phenotype of PCE rats is independent of value-based processing and is instead related to augmented reinforcing efficiency of opioid rewards. Our findings reveal that in utero THC exposure leads to increased cue-evoked dopamine release responses and an overrepresentation of cue-aligned, effort-driven striatal patterns of encoding. Recapitulating findings in humans, drug-related neurobiological adaptations of PCE were more pronounced in males, who similarly showed increased vulnerability for relapse. Collectively, these findings indicate that prenatal THC exposure in male rats engenders a pronounced neurodevelopmental susceptibility to addiction-like disorders later in life.

Characterization of cannabinoid plasma concentration, maternal health, and cytokine levels in a rat model of prenatal Cannabis smoke exposure

Cannabis sativa has gained popularity as a "natural substance", leading many to falsely assume that it is not harmful. This assumption has been documented amongst pregnant mothers, many of whom consider Cannabis use during pregnancy as benign. The purpose of this study was to validate a Cannabis smoke exposure model in pregnant rats by determining the plasma levels of cannabinoids and associated metabolites in the dams after exposure to either Cannabis smoke or injected cannabinoids. Maternal and fetal cytokine and chemokine profiles were also assessed after exposure. Pregnant Sprague-Dawley rats were treated daily from gestational day 6-20 with either room air, i.p. vehicle, inhaled high-Δ9-tetrahydrocannabinol (THC) (18% THC, 0.1% cannabidiol [CBD]) smoke, inhaled high-CBD (0.7% THC, 13% CBD) smoke, 3 mg/kg i.p. THC, or 10 mg/kg i.p. CBD. Our data reveal that THC and CBD, but not their metabolites, accumulate in maternal plasma after repeated exposures. Injection of THC or CBD was associated with fewer offspring and increased uterine reabsorption events. For cytokines and chemokines, injection of THC or CBD up-regulated several pro-inflammatory cytokines compared to control or high-THC smoke or high-CBD smoke in placental and fetal brain tissue, whereas smoke exposure was generally associated with reduced cytokine and chemokine concentrations in placental and fetal brain tissue compared to controls. These results support existing, but limited, knowledge on how different routes of administration contribute to inconsistent manifestations of cannabinoid-mediated effects on pregnancy. Smoked Cannabis is still the most common means of human consumption, and more preclinical investigation is needed to determine the effects of smoke inhalation on developmental and behavioural trajectories.

The Atypical Dopamine Transporter Inhibitor CE-158 Enhances Dopamine Neurotransmission in the Prefrontal Cortex of Male Rats: A Behavioral, Electrophysiological, and Microdialysis Study

BACKGROUND

Dopamine plays a key role in several physiological functions such as motor control, learning and memory, and motivation and reward. The atypical dopamine transporter inhibitor S,S stereoisomer of 5-(((S)-((S)-(3-bromophenyl)(phenyl)methyl)sulfinyl)methyl)thiazole (CE-158) has been recently reported to promote behavioral flexibility and restore learning and memory in aged rats.

METHODS

Adult male rats were i.p. administered for 1 or 10 days with CE-158 at the dose of 1 or 10 mg/kg and tested for extracellular dopamine in the medial prefrontal cortex by means of intracerebral microdialysis and single unit cell recording in the same brain area. Moreover, the effects of acute and chronic CE-158 on exploratory behavior, locomotor activity, prepulse inhibition, working memory, and behavioral flexibility were also investigated.

RESULTS

CE-158 dose-dependently potentiated dopamine neurotransmission in the medial prefrontal cortex as assessed by intracerebral microdialysis. Moreover, repeated exposure to CE-158 at 1 mg/kg was sufficient to increase the number of active pyramidal neurons and their firing frequency in the same brain area. In addition, CE-158 at the dose of 10 mg/kg stimulates exploratory behavior to the same extent after acute or chronic treatment. Noteworthy, the chronic treatment at both doses did not induce any behavioral alterations suggestive of abuse potential (e.g., motor behavioral sensitization) or pro-psychotic-like effects such as disruption of sensorimotor gating or impairments in working memory and behavioral flexibility as measured by prepulse inhibition and Y maze.

CONCLUSIONS

Altogether, these findings confirm CE-158 as a promising pro-cognitive agent and contribute to assessing its preclinical safety profile in a chronic administration regimen for further translational testing.

A comprehensive evaluation of adverse childhood experiences, social-emotional impairments, and neurodevelopmental disorders in cannabis-use disorder: Implications for clinical practice

BACKGROUND

Adverse childhood experiences (ACEs), social-emotional impairments (SEIs), and neurodevelopmental disorders (NDs) are frequent in psychiatric disorders, including substance-use disorders. We aimed to determine the prevalence of ACE, SEI, or ND in individuals with cannabis-use disorder (CUD). We compared individuals with preCUD-onset ACE, SEI, or ND to those without.

METHODS

We crosssectionally studied 323 inpatients or outpatients with a history of past or current CUD, aged 12-35 years (mean age 22.94 ± 4.79), 64.5% of whom were male. The sample was divided into two groups: the non-premorbid (N = 52) and the premorbid ACE/SEI/ND group (N = 271). Within the premorbid group, further subgroups were based on ACEs, SEI, and NDs. We also analyzed other substance use and psychiatric symptoms/diagnoses based on the non-premorbid-premorbid dichotomy in the CUD sample.

RESULTS

Pre-CUD ACE-SEI-ND had higher prevalence of bipolar, schizoaffective, borderline personality, and attention-deficit/hyperactivity disorders, and a history of agitation, hallucinations, and self-injury. The ACE group had higher rates of agitation, depression, delusions, hallucinations, eating disorders, and use of cocaine, amphetamines, and hallucinogens than the SEI or ND. Patients in the premorbid group initiated cannabis use at an earlier age, experienced the first comorbid psychiatric episode earlier, and were hospitalized earlier than those in the non- premorbid ACE-SEI-ND group.

CONCLUSIONS

PreCUD-onset ACE, SEI, or ND conditions in individuals with CUDare linked to earlier onset of comorbid mental illness. Furthermore, ACEs contribute to significant and potentially severe clinical symptoms, as well as the use of substances other than cannabis.

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.

Influence of prenatal cannabinoid exposure on early development and beyond

Public perception surrounding whether cannabis use is harmful during pregnancy often diverges greatly from the recommendations of doctors and healthcare providers. In contrast to the medical guidance of abstinence before, during, and after pregnancy, many women of reproductive age believe cannabis use during pregnancy is associated with little potential harm. Legalization and social cues support public perceptions that cannabis use during pregnancy is safe. Moreover, pregnant women may consider cannabis to be a safe alternative for treating pregnancy related ailments, including morning sickness. Compounding the problem is a lack of medical and federal guidance on safe, low, or high-risk levels of cannabis use. These issues mirror the continuing debate surrounding alcohol use and health, in particular, whether there are safe or lower risk levels of alcohol consumption during pregnancy. Clinical studies to date suffer from several limitations. First, most human studies are correlative in nature, meaning that causal associations cannot be made between in utero cannabis exposure and health and behavioral outcomes later in life. Due to obvious ethical constraints, it is not possible to randomly assign pregnant mothers to cannabis or other drug exposure conditions-a requirement needed to establish causality. In addition, clinical studies often lack quantitative information on maternal exposure (i.e., dose, frequency, and duration), include a small number of individuals, lack replication of outcome measures across cohorts, rely on self-report to establish maternal drug use, and suffer from unmeasured or residual confounding factors. Causal associations between maternal cannabis exposure and offspring outcomes are possible in preclinical cohorts but there is a large amount of heterogeneity across study designs and developmental differences between rodents and humans may limit translatability. In this review, we summarize research from human and preclinical models to provide insight into potential risks associated with prenatal cannabinoid exposure (PCE). Finally, we highlight gaps in knowledge likely to contribute to the growing divide between medical guidance and public attitudes regarding cannabis use during pregnancy.

Sperm DNA methylation alterations from cannabis extract exposure are evident in offspring

Background

Cannabis legalization is expanding and men are the predominant users. We have limited knowledge about how cannabis impacts sperm and whether the effects are heritable.

Results

Whole genome bisulfite sequencing (WGBS) data were generated for sperm of rats exposed to: (1) cannabis extract (CE) for 28 days, then 56 days of vehicle only (~ one spermatogenic cycle); (2) vehicle for 56 days, then 28 days of CE; or (3) vehicle only. Males were then mated with drug-naïve females to produce F1 offspring from which heart, brain, and sperm tissues underwent analyses. There were 3321 nominally significant differentially methylated CpGs in F0 sperm identified via WGBS with select methylation changes validated via bisulfite pyrosequencing. Significant methylation changes validated in F0 sperm of the exposed males at the gene 2-Phosphoxylose Phosphatase 1 (Pxylp1) were also detectable in their F1 sperm but not in controls. Changes validated in exposed F0 sperm at Metastasis Suppressor 1-Like Protein (Mtss1l) were also present in F1 hippocampal and nucleus accumbens (NAc) of the exposed group compared to controls. For Mtss1l, a significant sex-specific relationship between DNA methylation and gene expression was demonstrated in the F1 NAc. Phenotypically, rats born to CSE-exposed fathers exhibited significant cardiomegaly relative to those born to control fathers.

Conclusions

This is the first characterization of the effect of cannabis exposure on the entirety of the rat sperm methylome. We identified CE-associated methylation changes across the sperm methylome, some of which persisted despite a “washout” period. Select methylation changes validated via bisulfite pyrosequencing, and genes associated with methylation changes were involved in early developmental processes. Preconception CE exposure is associated with detectable changes in offspring DNA methylation that are functionally related to changes in gene expression and cardiomegaly.

These results support that paternal preconception exposure to cannabis can influence offspring outcomes.

Transgenerational Sex-dependent Disruption of Dopamine Function Induced by Maternal Immune Activation

Several epidemiological studies suggest an association between maternal infections during pregnancy and the emergence of neurodevelopmental disorders in the offspring, such as autism and schizophrenia. Animal models broadened the knowledge about the pathophysiological mechanisms that develop from prenatal infection to the onset of psychopathological phenotype. Mounting evidence supports the hypothesis that detrimental effects of maternal immune activation might be transmitted across generations. Here, we explored the transgenerational effects on the dopamine system of a maternal immune activation model based on the viral mimetic polyriboinosinic-polyribocytidilic acid. We assessed dopamine neurons activity in the ventral tegmental area by in vivo electrophysiology. Furthermore, we studied two behavioral tests strictly modulated by the mesolimbic dopamine system, i.e., the open field in response to amphetamine and the prepulse inhibition of the startle reflex in response to the D2 agonist apomorphine. Second-generation adult male rats did not display any deficit in sensorimotor gating; however, they displayed an altered activity of ventral tegmental area dopamine neurons, indexed by a reduced spontaneous firing rate and a heightened motor activation in response to amphetamine administration in the open field. On the other hand, second-generation female rats were protected from ancestors' polyriboinosinic-polyribocytidilic acid treatment, as they did not show any alteration in dopamine cell activity or in behavioral tests. These results confirm that maternal immune activation negatively influences, in a sex-dependent manner, neurodevelopmental trajectories of the dopamine system across generations.

Effects of Prenatal Nicotine, THC, or Co-Exposure on Cognitive Behaviors in Adolescent Male and Female Rats

INTRODUCTION

Although there has been a decrease in the prevalence of tobacco smoking, exposure to nicotine during pregnancy remains a substantial problem worldwide. Further, given the recent escalation in e-cigarette use and legalization of cannabis, it has become essential to understand the effects of nicotine and cannabinoid co-exposure during early developmental stages.

AIMS AND METHODS

We systematically examined the effects of nicotine and/or THC prenatal exposure on cognitive behaviors in male and female offspring. Dams were exposed to nicotine vape or vehicle, and oral edible THC or vehicle, throughout pregnancy. Adolescent offspring were then tested in the prepulse inhibition test, novel object recognition task, and novelty suppressed feeding task.

RESULTS

At birth, pups from mothers exposed to nicotine vape or oral THC exhibited reduced body weight, compared to control pups. Prenatal nicotine vape exposure resulted in a decreased baseline startle reactivity in adolescent male and female rats, and in females, enhanced sensorimotor gating in the prepulse inhibition test. Prenatal nicotine and THC co-exposure resulted in significant deficits in the prepulse inhibition test in males. Deficits in short-term memory were also found in males prenatally exposed to THC, either alone or with nicotine co-exposure, and in females exposed to THC alone. Finally, in males, a modest increase in anxiety-associated behaviors was found with THC or nicotine exposure in the latency to approach a novel palatable food.

CONCLUSIONS

These studies demonstrate differential effects of prenatal exposure to e-cigarette nicotine vape and/or edible THC on cognitive function, with differing effects within male and female groups.

IMPLICATIONS

These studies demonstrate an impact of nicotine, THC, or co-exposure during early developmental stages in utero on behavioral outcomes in adolescence. These findings have important translational implications given the continued use of nicotine and THC containing products by pregnant women worldwide, which can be applied to support healthcare and policy efforts restricting nicotine and THC use during pregnancy.

Cannabinoids: Emerging developments in neuropsychopharmacology and biological psychiatry

Cannabinoids from the cannabis plant were one of the earliest psychoactive phytochemicals harnessed by humanity for their medicinal properties and remain one of the most frequently used and misused classes of chemicals in the world. Despite our long-standing history with cannabinoids, much more is said than is known regarding how these molecules influence the brain and behavior. We are in a rapidly evolving discovery phase regarding the neuroscience of cannabinoids. This period of insight began in the mid-1990s when it was discovered that phytocannabinoids (e.g., delta-9-tetrahydrocannabinol) act on G protein-coupled receptors (i.e., CB₁/CB₂) in the brain to produce their psychoactive effects. Shortly thereafter, it was discovered that endogenous ligands (i.e., endocannabinoids) exist for these receptor targets and, that they are synthetized on demand under a variety of physiological conditions. Thus, we can now study how phytochemicals, endogenous ligands, and synthetic/metabolic enzymes of the endocannabinoid system influence the brain and behavior by activating known receptor targets. Our increased ability to study cannabinoid interactions with the brain and behavior coincides with an increase in international interest in utilizing cannabinoids as a medicine. At the same time, the potency of, and administration routes by which cannabinoids are used is rapidly changing. And, these trends in cannabinoid misuse are producing lasting neural adaptations that have implications for mental health. In this special edition, we will summarize our recent period of discovery regarding how: 1) phytocannabinoids, synthetic cannabinoids and endocannabinoids act on the brain to produce behavioral effects; 2) cannabinoids can be harnessed to produce pharmacotherapeutic utility in the field of medicine; and 3) use of increasingly more cannabinoid variants through unique routes of administration alter the brain and behavior, especially when used in critical developmental periods like pregnancy and adolescence.

Prenatal THC Does Not Affect Female Mesolimbic Dopaminergic System in Preadolescent Rats

Cannabis use among pregnant women is increasing worldwide along with permissive sociocultural attitudes toward it. Prenatal cannabis exposure (PCE), however, is associated with adverse outcome among offspring, ranging from reduced birth weight to child psychopathology. We have previously shown that male rat offspring prenatally exposed to Δ9-tetrahydrocannabinol (THC), a rat model of PCE, exhibit extensive molecular, cellular, and synaptic changes in dopamine neurons of the ventral tegmental area (VTA), resulting in a susceptible mesolimbic dopamine system associated with a psychotic-like endophenotype. This phenotype only reveals itself upon a single exposure to THC in males but not females. Here, we characterized the impact of PCE on female behaviors and mesolimbic dopamine system function by combining in vivo single-unit extracellular recordings in anesthetized animals and ex vivo patch clamp recordings, along with neurochemical and behavioral analyses. We find that PCE female offspring do not show any spontaneous or THC-induced behavioral disease-relevant phenotypes. The THC-induced increase in dopamine levels in nucleus accumbens was reduced in PCE female offspring, even when VTA dopamine activity in vivo and ex vivo did not differ compared to control. These findings indicate that PCE impacts mesolimbic dopamine function and its related behavioral domains in a sex-dependent manner and warrant further investigations to decipher the mechanisms determining this sex-related protective effect from intrauterine THC exposure.