CB1 receptor stimulation in specific brain areas differently modulate anxiety-related behaviour

The lateral septum partakes the regulation of propofol-induced anxiety-like behavior

Repeated exposure to propofol during early brain development is associated with anxiety disorders in adulthood, yet the mechanisms underlying propofol-induced susceptibility to anxiety disorders remain elusive. The lateral septum (LS), primarily composed of γ-aminobutyric acidergic (GABAergic) neurons, serves as a key brain region in the regulation of anxiety. However, it remains unclear whether LS GABAergic neurons are implicated in propofol-induced anxiety. Therefore, we conducted c-Fos immunostaining of whole-brain slices from mice exposed to propofol during early life. Our findings indicate that propofol exposure activates GABAergic neurons in the LS. Selective activation of LS GABAergic neurons resulted in increased anxiety-like behavior, while selective inhibition of these neurons reduced such behaviors. These results suggest that the LS is a critical brain region involved in propofol-induced anxiety. Furthermore, we investigated the molecular mechanism of propofol-induced anxiety in the LS. Microglia activation underlies the development of anxiety. Immunofluorescence staining and Western blot analysis of LS revealed activated microglia and significantly elevated levels of phospho-NF-κB p65 protein. Additionally, a decrease in the number of neuronal spines was observed. Our study highlights the crucial role of the LS in the development of anxiety-like behavior in adulthood following childhood propofol exposure, accompanied by the activation of inflammatory pathways.

UK Medical Cannabis Registry: a case series analyzing clinical outcomes of medical cannabis therapy for generalized anxiety disorder patients

This study aims to analyze changes in health-related quality of life (HRQoL) and safety in patients with generalized anxiety disorder (GAD) prescribed a homogenous selection of cannabis-based medicinal products (CBMPs). Patients prescribed Adven CBMPs (Curaleaf International, UK) for GAD were identified from the UK Medical Cannabis Registry. Primary outcomes were changes in patient-reported outcome measures (PROMs) from baseline up to 12 months, including GAD-7, Single-Item Sleep Quality Scale (SQS), and EQ-5D-5L. Adverse events were recorded using CTCAE version 4.0. A total of 120 patients were identified for inclusion, of which 38 (31.67%), 52 (43.33%), and 30 (25.00%) were prescribed oils, dried flower, and both formulations of CBMP. Associated improvements in GAD-7, SQS, and EQ-5D-5L at 1, 3, 6, and 12 months were observed compared to baseline (P < 0.010). There were 24 (20.00%) patients who reported 442 (368.33%) adverse events, most of which were mild (n = 184, 41.63%) and moderate (n = 197, 44.57%). This study reports an association between initiation of a homogeneous CBMP therapy and improvements in anxiety severity and HRQoL in individuals with GAD. Moreover, therapy was well-tolerated at 12 months follow-up. Further investigation through randomized controlled trials will ultimately be required to determine causation.

Basolateral Amygdala Cannabinoid CB1 Receptor Controls Formation and Elimination of Social Fear Memory

Patients with post-traumatic stress disorder (PTSD) usually manifest persistence of the traumatic memory for a long time after the event, also known as resistance to extinction learning. Numerous studies have shown that the endocannabinoid system, specifically the cannabinoid type-1 receptor (CB1R), plays an important role in traumatic memory. However, the effect of basolateral amygdala (BLA) CB1R in social fear memory formation and elimination is still unclear. Here, we built a mouse model of social avoidance induced by acute social defeat stress to investigate the role of BLA CB1R in social fear memory formation and anxiety- and depression-like behavior. Anterograde knockout of CB1R in BLA neurons facilitates social fear memory formation and manifests an anxiolytic effect but does not influence sociability and social novelty. Retrograde knockout of CB1R in BLA promotes social fear memory formation and shows an anxiogenic effect but does not affect sociability and social novelty. Moreover, intracerebral injection of the CB1R antagonist AM251 in BLA during the memory reconsolidation time window eliminates social fear memory. Our findings suggest the CB1R of BLA can be used as a novel molecular target in social fear memory formation and elimination and potential PTSD therapy with memory retrieval and AM251.

Cannabinoids in Medicine: A Multifaceted Exploration of Types, Therapeutic Applications, and Emerging Opportunities in Neurodegenerative Diseases and Cancer Therapy

In this review article, we embark on a thorough exploration of cannabinoids, compounds that have garnered considerable attention for their potential therapeutic applications. Initially, this article delves into the fundamental background of cannabinoids, emphasizing the role of endogenous cannabinoids in the human body and outlining their significance in studying neurodegenerative diseases and cancer. Building on this foundation, this article categorizes cannabinoids into three main types: phytocannabinoids (plant-derived cannabinoids), endocannabinoids (naturally occurring in the body), and synthetic cannabinoids (laboratory-produced cannabinoids). The intricate mechanisms through which these compounds interact with cannabinoid receptors and signaling pathways are elucidated. A comprehensive overview of cannabinoid pharmacology follows, highlighting their absorption, distribution, metabolism, and excretion, as well as their pharmacokinetic and pharmacodynamic properties. Special emphasis is placed on the role of cannabinoids in neurodegenerative diseases, showcasing their potential benefits in conditions such as Alzheimer's disease, Parkinson's disease, Huntington's disease, and multiple sclerosis. The potential antitumor properties of cannabinoids are also investigated, exploring their potential therapeutic applications in cancer treatment and the mechanisms underlying their anticancer effects. Clinical aspects are thoroughly discussed, from the viability of cannabinoids as therapeutic agents to current clinical trials, safety considerations, and the adverse effects observed. This review culminates in a discussion of promising future research avenues and the broader implications for cannabinoid-based therapies, concluding with a reflection on the immense potential of cannabinoids in modern medicine.

Hippocampus: Molecular, Cellular, and Circuit Features in Anxiety

Anxiety disorders are currently a major psychiatric and social problem, the mechanisms of which have been only partially elucidated. The hippocampus serves as a major target of stress mediators and is closely related to anxiety modulation. Yet so far, its complex anatomy has been a challenge for research on the mechanisms of anxiety regulation. Recent advances in imaging, virus tracking, and optogenetics/chemogenetics have permitted elucidation of the activity, connectivity, and function of specific cell types within the hippocampus and its connected brain regions, providing mechanistic insights into the elaborate organization of the hippocampal circuitry underlying anxiety. Studies of hippocampal neurotransmitter systems, including glutamatergic, GABAergic, cholinergic, dopaminergic, and serotonergic systems, have contributed to the interpretation of the underlying neural mechanisms of anxiety. Neuropeptides and neuroinflammatory factors are also involved in anxiety modulation. This review comprehensively summarizes the hippocampal mechanisms associated with anxiety modulation, based on molecular, cellular, and circuit properties, to provide tailored targets for future anxiety treatment.

Activation of ventral hippocampal CB1 receptors inhibits ketamine-induced anxiogenic-like behavior: Alteration of BDNF/c-Fos levels in the mouse hippocampus

Considering the increasing usage of ketamine as a recreational drug with hallucinogenic properties and also scarce studies about receptor systems responsible for its effects, in the present study we aimed to investigate whether the activation of the ventral hippocampal (VH) CB1 cannabinoid receptors affects the anxiety-like behaviors induced by ketamine. Also, the levels of BDNF and c-Fos proteins in the mouse hippocampus were measured following the treatments. For this purpose, male NMRI mice were cannulated bilaterally in the VH with a stereotaxic apparatus. Anxiety properties and protein changes were measured using elevated plus-maze (EPM) and western blotting respectively. The results revealed that intraperitoneal (i.p.) administration of ketamine (5-20 mg/kg) significantly decreased the percentage of open arm time (%OAT) and open arm entry (%OAE) in the EPM with no alteration in the locomotor activity suggesting an anxiogenic-like behavior to ketamine. Furthermore, ketamine administration (10 mg/kg, i.p.) increased BDNF and c-Fos levels in the hippocampus. Interestingly, activation of the VH CB1 receptors by ACPA (0.5-4 ng/mouse) inhibited the anxiogenic-like behaviors produced by ketamine, whereas the microinjection of the same doses of ACPA into VH by itself had no effect on the EPM parameters. Hippocampal levels of BDNF and c-Fos decreased after treatment with combined ketamine with ACPA. These results suggest the therapeutic potency of cannabinoid receptor agonists for ketamine-induced anxiogenic-related responses. This effect might be at least partially mediated by the alteration of BDNF and c-Fos signaling in the hippocampus.

Bed nucleus of the stria terminalis CB1 receptors and the FAAH enzyme modulate anxiety behavior depending on previous stress exposure

The endocannabinoid (eCB) anandamide (AEA) is synthesized on-demand in the post-synaptic terminal and can act on presynaptic cannabinoid type 1 (CB1) receptors, decreasing the release of neurotransmitters, including glutamate. AEA action is ended through enzymatic hydrolysis via FAAH (fatty acid amid hydrolase) in the post-synaptic neuron. eCB system molecules are widely expressed in brain areas involved in the modulation of fear and anxiety responses, including the Bed Nucleus of the Stria Terminalis (BNST), which is involved in the integration of autonomic, neuroendocrine, and behavioral regulation. The presence of the CB1 and FAAH was described in the BNST; however, their role in the modulation of defensive reactions is not fully comprehended. In the present work we aimed at investigating the role of AEA and CB1 receptors in the BNST in modulating anxiety-related behaviors. Adult male Wistar rats received local BNST injections of the CB1 receptor antagonist AM251 (0.1-0.6 nmol) and/or the FAAH inhibitor (URB597; 0.001-0.1 nmol) and were evaluated in the elevated plus maze (EPM) test, with or without previous acute restraint stress (2 h) exposure, or in the contextual fear conditioning. We observed that although AM251 and URB597 had no effects on the EPM, they increased and decreased, respectively, the conditioned fear response. Supporting a possible influence of stress in these differences, URB597 was able to prevent the restraint stress-induced anxiogenic effect in the EPM. The present data, therefore, suggest that eCB signaling in the BNST is recruited during more aversive situations to counteract the stress effect.

Ventral hippocampal diacylglycerol lipase-alpha deletion decreases avoidance behaviors and alters excitation-inhibition balance

The endogenous cannabinoid, 2-arachidonoylglycerol (2-AG), plays a key role in the regulation of anxiety- and stress-related behavioral phenotypes and may represent a novel target for the treatment of anxiety disorders. However, recent studies have suggested a more complex role for 2-AG signaling in the regulation of stress responsivity, including increases in acute fear responses after 2-AG augmentation under some conditions. Thus, 2-AG signaling within distinct brain regions and circuits could regulate anxiety-like behavior and stress responsivity in opposing manners. The ventral hippocampus (vHPC) is a critical region for emotional processing, anxiety-like behaviors, and stress responding. Here, we use a conditional knock-out of the 2-AG synthesis enzyme, diacylglycerol lipase α (DAGLα), to study the role of vHPC 2-AG signaling in the regulation of affective behavior. We show that vHPC DAGLα deletion decreases avoidance behaviors both basally and following an acute stress exposure. Genetic deletion of vHPC DAGLα also promotes stress resiliency, with no effect on fear acquisition, expression, or contextual fear generalization. Using slice electrophysiology, we demonstrate that vHPC DAGLα deletion shifts vHPC activity towards enhanced inhibition. Together, these data indicate endogenous 2-AG signaling in the vHPC promotes avoidance and increases stress reactivity, confirming the notion that 2-AG signaling within distinct brain regions may exert divergent effects on anxiety states and stress adaptability.

THC, CBD, and Anxiety: A review of recent findings on the anxiolytic and anxiogenic effects of cannabis' primary cannabinoids

Purpose of review

In the context of ongoing decriminalization and legalization of cannabis, a better understanding of how THC and CBD impact anxiety is critical to elucidate the risks of recreational cannabis use as well as to establish the therapeutic potential of cannabis products for anxiety-related applications.

Recent findings

Recent literature supports anxiogenic effects of THC administration, which may be attenuated among regular cannabis users. Data regarding anxiolytic effects of CBD administration are mixed. Most newer studies contradict earlier findings in reporting no effects of CBD on anxiety in healthy participants, whereas inconsistent results have been reported among individuals with anxiety disorders, substance use disorders, and other clinical populations.

Summary

Future research is needed to reconcile heterogenous findings, explore sex differences in the effects of THC and CBD on anxiety, as well as to assess how effects change with extended exposure, the impact of different CBD doses, and interactions between THC, CBD, and other cannabis compounds.

Fatty acid amide hydrolase inhibition and N-arachidonoylethanolamine modulation by isoflavonoids: A novel target for upcoming antidepressants

Modulation of the endocannabinoid system (ECS) is a novel putative target for therapeutic intervention in depressive disorders. Altering concentrations of one of the principal endocannabinoids, N‐arachidonoylethanolamine, also known as anandamide (AEA) can affect depressive‐like behaviors through several mechanisms including anti‐inflammatory, hormonal, and neural circuit alterations. Recently, isoflavonoids, a class of plant‐derived compounds, have been of therapeutic interest given their ability to modulate the metabolism of the endogenous ligands of the ECS. To determine the therapeutic potential of isoflavonoids, we screened several candidate compounds (Genistein, Biochanin‐A, and 7‐hydroxyflavone) in silico to determine their binding properties with fatty acid amide hydrolase (FAAH), the primary degrative enzyme for AEA. We further validated the ability of these compounds to inhibit FAAH and determined their effects on depressive‐like and locomotor behaviors in the forced swim test (FST) and open field test in male and female mice. We found that while genistein was the most potent FAAH inhibitor, 7‐hydroxyflavone was most effective at reducing immobility time in the forced swim test. Finally, we measured blood corticosterone and prefrontal cortex AEA concentrations following the forced swim test and found that all tested compounds decreased corticosterone and increased AEA, demonstrating that isoflavonoids are promising therapeutic targets as FAAH inhibitors.

Increased cannabis intake during the COVID-19 pandemic is associated with worsening of depression symptoms in people with PTSD

BACKGROUND

Some evidence suggests substance use affects clinical outcomes in people with posttraumatic stress disorder (PTSD). However, more work is required to examine links between mental health and cannabis use in PTSD during exposure to external stressors such as the COVID-19 pandemic. This study assessed mental health factors in individuals with self-reported PTSD to: (a) determine whether stress, anxiety, and depression symptoms were associated with changes in cannabis consumption across the pandemic, and (b) to contrast the degree to which clinically significant perceived symptom worsening was associated with changes in cannabis intake.

METHOD

Data were obtained as part of a larger web-based population survey from April 3rd to June 24th 2020 (i.e., first wave of the pandemic in Canada). Participants (N = 462) with self-reported PTSD completed questionnaires to assess mental health symptoms and answered questions pertaining to their cannabis intake. Participants were categorized according to whether they were using cannabis or not, and if using, whether their use frequency increased, decreased, or remained unchanged during the pandemic.

RESULTS

Findings indicated an overall perceived worsening of stress, anxiety, and depression symptoms across all groups. A higher-than-expected proportion of individuals who increased their cannabis consumption reached threshold for minimal clinically important worsening of depression, X²(3) = 10.795, p = 0.013 (Cramer's V = 0.166).

CONCLUSION

Overall, those who increased cannabis use during the pandemic were more prone to undergo meaningful perceived worsening of depression symptoms. Prospective investigations will be critical next steps to determine the directionality of the relationship between cannabis and depressive symptoms.

Safety and Efficacy of Medical Cannabis in Autism Spectrum Disorder Compared with Commonly Used Medications

Objective: The objective of this study was to evaluate the safety and efficacy of medications commonly used in autism spectrum disorder (ASD) and compare this to what current research has shown regarding medical cannabis use in this population. Methods: Searches were performed to collect information surrounding currently used medications and their safety and efficacy profiles, biologic plausibility of cannabis use for symptoms of ASD, and studies detailing cannabis' safety and efficacy profile for use in the ASD population. Results were used to compare medications to cannabis as a proposed treatment. Results: The heterogeneity of ASD produces great difficulties in finding appropriate treatment, leading to many medication changes or treatment trials throughout a patient's life. Commonly prescribed medications display varying levels of efficacy, safety, and tolerability between patients and symptoms targeted. Some of the most common side effects cited are also considered the most troubling symptoms associated with ASD; aggression, anxiety, irritability, and a negative effect on cognition, leading many patients to discontinue use as the side effects outweigh benefits. Recent case reports and retrospective studies have displayed the potential efficacy, safety, and tolerability of cannabidiol (CBD)-rich medical cannabis use for treating both core symptoms of ASD and many comorbid symptoms such as irritability and sleep problems. Studies have also identified circulating endocannabinoids as a possible biomarker for ASD, providing another possible method of diagnosis. Conclusions: Currently, there are no approved medications for the core symptoms of ASD and only two medications Food and Drug Administration approved for associated irritability. Prescribed medications for symptoms associated with ASD display varying levels of efficacy, safety, and tolerability among the heterogeneous ASD population. At the time of this study there are no published placebo-controlled trials of medical cannabis for ASD and the observational studies have limitations. CBD-rich medical cannabis seems to be an effective, tolerable, and relatively safe option for many symptoms associated with ASD, however, the long-term safety is unknown at this time.

Effects of endocannabinoid system modulation on social behaviour: A systematic review of animal studies

There is a clear link between psychiatric disorders and social behaviour, and evidence suggests the involvement of the endocannabinoid system (ECS). A systematic review of preclinical literature was conducted using MEDLINE (PubMed) and PsychINFO databases to examine whether pharmacological and/or genetic manipulations of the ECS alter social behaviours in wildtype (WT) animals or models of social impairment (SIM). Eighty studies were included. Risk of bias (RoB) was assessed using SYRCLE's RoB tool. While some variability was evident, studies most consistently found that direct cannabinoid receptor (CBR) agonism decreased social behaviours in WT animals, while indirect CBR activation via enzyme inhibition or gene-knockout increased social behaviours. Direct and, more consistently, indirect CBR activation reversed social deficits in SIM. These CBR-mediated effects were often sex- and developmental-phase-dependent and blocked by CBR antagonism. Overall, ECS enzyme inhibition may improve social behaviour in SIM, suggesting the potential usefulness of ECS enzyme inhibition as a therapeutic approach for social deficits. Future research should endeavour to elucidate ECS status in neuropsychiatric disorders characterized by social deficits.

Higher trait neuroticism is associated with greater fatty acid amide hydrolase binding in borderline and antisocial personality disorders

Borderline personality disorder (BPD) and antisocial personality disorder (ASPD) are the two most frequently diagnosed and researched DSM-5 personality disorders, and both are characterized by high levels of trait neuroticism. Fatty acid amide hydrolase (FAAH), an enzyme of the endocannabinoid system (ECS), has been linked to regulation of mood through modulation of anandamide, an endocannabinoid. We hypothesized that prefrontal cortex (PFC) FAAH binding would relate to trait neuroticism in personality disorders. Thirty-one individuals with personality disorders (20 with BPD and 11 with ASPD) completed the investigation. All participants completed the revised NEO Personality Inventory, which yields standardized scores (e.g., T scores) for the traits of neuroticism, openness, conscientiousness, agreeableness, and extraversion. All participants were medication free and were not utilizing illicit substances as determined by drug urinalysis. Additionally, none of the participants had a comorbid major depressive episode, bipolar disorder, psychotic disorder, or substance use disorder. Each participant underwent one [¹¹C]CURB PET scan. Consistent with our hypothesis, neuroticism was positively correlated with PFC FAAH binding (r = 0.42, p = 0.021), controlling for genotype. Neuroticism was also positively correlated with dorsal putamen FAAH binding (r = 0.53, p = 0.0024), controlling for genotype. Elevated brain FAAH is an endophenotype for high neuroticism in BPD and ASPD. Novel pharmacological therapeutics that inhibit FAAH could emerge as potential new treatments for BPD and ASPD with high neuroticism.

Cannabis containing equivalent concentrations of delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD) induces less state anxiety than THC-dominant cannabis

RATIONALE

Delta-9-tetrahydrocannabinol (THC), an active component of cannabis, can cause anxiety in some users during intoxication. Cannabidiol (CBD), another constituent of cannabis, has anxiolytic properties suggesting that cannabis products containing CBD in addition to THC may produce less anxiety than THC-only products. Findings to date around this issue have been inconclusive and could conceivably depend on moderating factors such as baseline anxiety levels in users.

OBJECTIVE

The present study examined whether anxiety following single doses of vaporised THC, CBD and THC/CBD might be explained by state and trait anxiety levels at baseline.

METHODS

A placebo-controlled, randomised, within-subjects study including 26 healthy recreational cannabis users tested the effects of vaporised THC-dominant cannabis (13.75 mg THC), CBD-dominant cannabis (13.75 mg CBD), THC/CBD-equivalent cannabis (13.75 mg THC/13.75 mg CBD) and placebo cannabis on anxiety. Self-rated trait anxiety was assessed with the State-Trait Anxiety Inventory (STAI). State levels of anxiety were objectively assessed with a computer-based emotional Stroop task (EST) and subjectively rated with the STAI-state questionnaire and a visual analogue scale.

RESULTS

Both THC and THC/CBD significantly increased self-rated state anxiety compared to placebo. State anxiety after THC/CBD was significantly lower than after THC alone. THC-induced anxiety was independent of anxiety at baseline. When baseline anxiety was low, CBD completely counteracted THC-induced anxiety; however, when baseline anxiety was high, CBD did not counteract THC-induced anxiety. There were no effects of any treatment condition on the EST.

CONCLUSION

Overall, the study demonstrated that the THC/CBD-equivalent cannabis induces less state anxiety than THC-dominant cannabis.

Receptor mechanisms underlying the CNS effects of cannabinoids: CB1 receptor and beyond

Cannabis legalization continues to progress in many US states and other countries. Δ9-tetrahydrocannabinol (Δ9-THC) is the major psychoactive constituent in cannabis underlying both its abuse potential and the majority of therapeutic applications. However, the neural mechanisms underlying cannabis action are not fully understood. In this chapter, we first review recent progress in cannabinoid receptor research, and then examine the acute CNS effects of Δ9-THC or other cannabinoids (WIN55212-2) with a focus on their receptor mechanisms. In experimental animals, Δ9-THC or WIN55212-2 produces classical pharmacological effects (analgesia, catalepsy, hypothermia, hypolocomotion), biphasic changes in affect (reward vs. aversion, anxiety vs. anxiety relief), and cognitive deficits (spatial learning and memory, short-term memory). Accumulating evidence indicates that activation of CB1Rs underlies the majority of Δ9-THC or WIN55121-2's pharmacological and behavioral effects. Unexpectedly, glutamatergic CB1Rs preferentially underlie cannabis action relative to GABAergic CB1Rs. Functional roles for CB1Rs expressed on astrocytes and mitochondria have also been uncovered. In addition, Δ9-THC or WIN55212-2 is an agonist at CB2R, GPR55 and PPARγ receptors and recent studies implicate these receptors in a number of their CNS effects. Other receptors (such as serotonin, opioid, and adenosine receptors) also modulate Δ9-THC's actions and their contributions are detailed. This chapter describes the neural mechanisms underlying cannabis action, which may lead to new discoveries in cannabis-based medication development for the treatment of cannabis use disorder and other human diseases.

Modulation of Neurolipid Signaling and Specific Lipid Species in the Triple Transgenic Mouse Model of Alzheimer's Disease

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder and the most common cause of dementia in aging populations. Recently, the regulation of neurolipid-mediated signaling and cerebral lipid species was shown in AD patients. The triple transgenic mouse model (3xTg-AD), harboring βAPP_Swe, PS1_M146V, and tau_P301L transgenes, mimics many critical aspects of AD neuropathology and progressively develops neuropathological markers. Thus, in the present study, 3xTg-AD mice have been used to test the involvement of the neurolipid-based signaling by endocannabinoids (eCB), lysophosphatidic acid (LPA), and sphingosine 1-phosphate (S1P) in relation to the lipid deregulation. [³⁵S]GTPγS autoradiography was used in the presence of specific agonists WIN55,212-2, LPA and CYM5442, to measure the activity mediated by CB₁, LPA₁, and S1P₁ G_i/0 coupled receptors, respectively. Consecutive slides were used to analyze the relative intensities of multiple lipid species by MALDI Mass spectrometry imaging (MSI) with microscopic anatomical resolution. The quantitative analysis of the astrocyte population was performed by immunohistochemistry. CB₁ receptor activity was decreased in the amygdala and motor cortex of 3xTg-AD mice, but LPA₁ activity was increased in the corpus callosum, motor cortex, hippocampal CA1 area, and striatum. Conversely, S1P₁ activity was reduced in hippocampal areas. Moreover, the observed modifications on PC, PA, SM, and PI intensities in different brain areas depend on their fatty acid composition, including decrease of polyunsaturated fatty acid (PUFA) phospholipids and increase of species containing saturated fatty acids (SFA). The regulation of some lipid species in specific brain regions together with the modulation of the eCB, LPA, and S1P signaling in 3xTg-AD mice indicate a neuroprotective adaptation to improve neurotransmission, relieve the myelination dysfunction, and to attenuate astrocyte-mediated neuroinflammation. These results could contribute to identify new therapeutic strategies based on the regulation of the lipid signaling in familial AD patients.

Brief Report: Suspected Cannabis-Induced Mania and Psychosis in Young Adult Males with Autism Spectrum Disorder

There is increasing interest in investigating cannabis for behavioral symptoms in individuals with autism spectrum disorder (ASD). The potential role of dysregulated cannabinoid signaling contributing to the pathophysiology of ASD is an area of active investigation. Results from retrospective and uncontrolled trials of cannabis in subjects with ASD have been published, reporting both potential benefits and adverse effects. Here, we describe the clinical course of three young adult males with ASD who developed mania or psychosis after the consistent use of cannabidiol and delta-9-tetrahydrocannabinol. Caution should be utilized with cannabis use in individuals with ASD until large-scale, replicated randomized controlled trials demonstrating efficacy, safety and tolerability have been published.

The endocannabinoid system in social anxiety disorder: from pathophysiology to novel therapeutics

Social anxiety disorder (SAD) is a highly prevalent psychiatric disorder that presents with an early age of onset, chronic disease course, and increased risk of psychiatric comorbidity. Current treatment options for SAD are associated with low response rates, suboptimal efficacy, and possible risk of adverse effects. Investigation of new neurobiological mechanisms may aid in the identification of more specific therapeutic targets for the treatment of this disorder. Emerging evidence suggests that the endogenous cannabinoid system, also referred to as the endocannabinoid system (ECS), could play a potential role in the pathophysiology of SAD. This review discusses the known pathophysiological mechanisms of SAD, the potential role of the ECS in this disorder, current drugs targeting the ECS, and the potential of these novel compounds to enhance the therapeutic armamentarium for SAD. Further investigational efforts, specifically in human populations, are warranted to improve our knowledge of the ECS in SAD.

CB1 and CB2 receptors in the bed nucleus of the stria terminalis differently modulate anxiety-like behaviors in rats

The endocannabinoid system is implicated in anxiety, but the brain sites involved are not completely understood. The bed nucleus of the stria terminalis (BNST) has been related to anxiety and responses to aversive threats. Besides, endocannabinoid neurotransmission acting via CB₁ receptors was identified in the BNST. However, the presence of CB₂ receptors and the role of BNST endocannabinoid system in anxiety-like behaviors have never been reported. Therefore, this study investigated the presence of CB₁ and CB₂ receptors in the BNST and their role in anxiety-like behaviors. For this, gene expression of the endocannabinoid receptors was evaluated in samples from anterior and posterior BNST. Besides, behaviors were evaluated in the elevated plus-maze (EPM) in unstressed rats (trait anxiety-like behavior) and after exposure to restraint stress (restraint-evoked anxiety-like behavior) in rats treated with either the CB₁ receptor antagonist AM251 or the CB₂ receptor antagonist JTE907 into the anterior BNST. The presence of CB₁ and CB₂ receptors gene expression was identified in anterior and posterior divisions of the BNST. Bilateral microinjection of AM251 into the anterior BNST dose-dependently increased EPM open arms exploration in unstressed animals and inhibited the anxiety-like behavior in the EPM evoked by restraint. Conversely, intra-BNST microinjection of JTE907 decreased EPM open arms exploration in a dose-dependent manner and inhibited restraint-evoked behavioral changes in the EPM. Taken together, these results indicate that CB₁ and CB₂ receptors present in the BNST are involved in control of anxiety-like behaviors, and control by the latter is affected by previous stress experience.

Sex differences in the acute effects of oral and vaporized cannabis among healthy adults

Policy changes have increased access to cannabis for individuals with little or no prior exposure. Few studies have examined sex differences in cannabis effects among individuals with sporadic cannabis use or for nonsmoked routes of cannabis administration. Data from four double-blind, placebo-controlled studies were pooled to compare the acute pharmacodynamic effects of vaporized and oral cannabis in male (n = 27) and female (n = 23) participants who used cannabis infrequently (no use ≥30 days prior to randomization). Analyses compared peak change-from-baseline scores between male and female participants for subjective drug effects, cognitive/psychomotor performance, cardiovascular effects, and blood concentrations of Δ9-tetrahydrocannabinol (THC) and its primary metabolites (11-OH-THC, THC-COOH) after exposure to placebo cannabis or cannabis containing low-dose (5 or 10 mg) or high-dose THC (20 or 25 mg). Overall, cannabis elicited dose-orderly increases in subjective effects, impairment of cognitive/psychomotor performance, heart rate, and blood cannabinoid concentrations. Females exhibited greater peak blood 11-OH-THC concentrations and reported greater peak subjective ratings of "drug effect" that remained when controlling for body weight. When controlling for both body weight and peak blood cannabinoid concentrations, ratings of "anxious/nervous," "heart racing," and "restless" were significantly higher for females than males. Although additional research is needed to elucidate sex differences in responses to cannabis at a wider range of THC doses, other routes of administration, and products with diverse chemical composition, the current data indicate that public health messaging and clinical decision making around the use of cannabinoids should recommend lower starting doses for females and warnings about acute anxiogenic reactions.

Endocannabinoid Receptors in the CNS: Potential Drug Targets for the Prevention and Treatment of Neurologic and Psychiatric Disorders

The endocannabinoid system participates in the regulation of CNS homeostasis and functions, including neurotransmission, cell signaling, inflammation and oxidative stress, as well as neuronal and glial cell proliferation, differentiation, migration and survival. Endocannabinoids are produced by multiple cell types within the CNS and their main receptors, CB₁ and CB₂, are expressed in both neurons and glia. Signaling through these receptors is implicated in the modulation of neuronal and glial alterations in neuroinflammatory, neurodegenerative and psychiatric conditions, including Alzheimer’s, Parkinson’s and Huntington’s disease, multiple sclerosis, amyotrophic lateral sclerosis, stroke, epilepsy, anxiety and depression. The therapeutic potential of endocannabinoid receptors in neurological disease has been hindered by unwelcome side effects of current drugs used to target them; however, due to their extensive expression within the CNS and their involvement in physiological and pathological process in nervous tissue, they are attractive targets for drug development. The present review highlights the potential applications of the endocannabinoid system for the prevention and treatment of neurologic and psychiatric disorders.

Endocannabinoids, cannabinoids and the regulation of anxiety

Cannabis has been used for hundreds of years, with its ability to dampen feelings of anxiety often reported as a primary reason for use. Only recently has the specific role cannabinoids play in anxiety been thoroughly investigated. Here we discuss the body of evidence describing how endocannabinoids and exogenous cannabinoids are capable of regulating the generation and termination of anxiety states. Disruption of the endogenous cannabinoid (eCB) system following genetic manipulation, pharmacological intervention or stress exposure reliably leads to the generation of an anxiety state. On the other hand, upregulation of eCB signaling is capable of alleviating anxiety-like behaviors in multiple paradigms. When considering exogenous cannabinoid administration, cannabinoid receptor 1 (CB1) agonists have a biphasic, dose-dependent effect on anxiety such that low doses are anxiolytic while high doses are anxiogenic, a phenomenon that is evident in both rodent models and humans. Translational studies investigating a loss of function mutation in the gene for fatty acid amide hydrolase, the enzyme responsible for metabolizing AEA, have also shown that AEA signaling regulates anxiety in humans. Taken together, evidence reviewed here has outlined a convincing argument for cannabinoids being powerful regulators of both the manifestation and amelioration of anxiety symptoms, and highlights the therapeutic potential of targeting the eCB system for the development of novel classes of anxiolytics. This article is part of the special issue on 'Cannabinoids'.

Endocannabinoid system in the neurodevelopment of GABAergic interneurons: implications for neurological and psychiatric disorders

In mature mammalian brains, the endocannabinoid system (ECS) plays an important role in the regulation of synaptic plasticity and the functioning of neural networks. Besides, the ECS also contributes to the neurodevelopment of the central nervous system. Due to the increase in the medical and recreational use of cannabis, it is inevitable and essential to elaborate the roles of the ECS on neurodevelopment. GABAergic interneurons represent a group of inhibitory neurons that are vital in controlling neural network activity. However, the role of the ECS in the neurodevelopment of GABAergic interneurons remains to be fully elucidated. In this review, we provide a brief introduction of the ECS and interneuron diversity. We focus on the process of interneuron development and the role of ECS in the modulation of interneuron development, from the expansion of the neural stem/progenitor cells to the migration, specification and maturation of interneurons. We further discuss the potential implications of the ECS and interneurons in the pathogenesis of neurological and psychiatric disorders, including epilepsy, schizophrenia, major depressive disorder and autism spectrum disorder.

Role of PPARs in Progression of Anxiety: Literature Analysis and Signaling Pathways Reconstruction

Peroxisome proliferator-activated receptor (PPAR) group includes three isoforms encoded by PPARG, PPARA, and PPARD genes. High concentrations of PPARs are found in parts of the brain linked to anxiety development, including hippocampus and amygdala. Among three PPAR isoforms, PPARG demonstrates the highest expression in CNS, where it can be found in neurons, astrocytes, and glial cells. Herein, the highest PPARG expression occurs in amygdala. However, little is known considering possible connections between PPARs and anxiety behavior. We reviewed possible connections between PPARs and anxiety. We used the Pathway Studio software (Elsevier). Signal pathways were created according to previously developed algorithms. SNEA was performed in Pathway Studio. Current study revealed 14 PPAR-regulated proteins linked to anxiety. Possible mechanism of PPAR involvement in neuroinflammation protection is proposed. Signal pathway reconstruction and reviewing aimed to reveal possible connection between PPARG and CCK-ergic system was conducted. Said analysis revealed that PPARG-dependent regulation of MME and ACE peptidase expression may affect levels of nonhydrolysed, i.e., active CCK-4. Impairments in PPARG regulation and following MME and ACE peptidase expression impairments in amygdala may be the possible mechanism leading to pathological anxiety development, with brain CCK-4 accumulation being a key link. Literature data analysis and signal pathway reconstruction and reviewing revealed two possible mechanisms of peroxisome proliferator-activated receptors involvement in pathological anxiety: (1) cytokine expression and neuroinflammation mechanism and (2) regulation of peptidases targeted to anxiety-associated neuropeptides, primarily CCK-4, mechanism.

The effectiveness of inhaled Cannabis flower for the treatment of agitation/irritability, anxiety, and common stress

BACKGROUND

An observational research design was used to evaluate which types of commonly labeled Cannabis flower product characteristics are associated with changes in momentary feelings of distress-related symptoms.

METHODS

We used data from 2306 patient-directed cannabis administration sessions among 670 people who used the real-time Cannabis effects recording software, Releaf App, between June 6, 2016, and February 23, 2019, for tracking the effects of Cannabis flower consumption. Fixed effects multivariable panel regression techniques were used to establish overall relief by symptom type and to determine which labeled product characteristics (e.g., subspecies/subtype, inhalation method, and major cannabinoid contents) showed the strongest correlation with changes in momentary feelings of agitation/irritability, anxiety, and stress, along with experienced side effects.

RESULTS

In total, a decrease in symptom intensity levels was reported in 95.51% of Cannabis usage sessions, an increase in 2.32% of sessions, and no change in 2.16% of sessions. Fixed effects models showed, on average, respondents recorded a maximum symptom intensity reduction of 4.33 points for agitation/irritability (SE = 0.20, p < 0.01), 3.47 points for anxiety (SE = 0.13, p < 0.01), and 3.98 for stress (SE = 0.12, p < 0.01) on an 11-point visual analog scale. Fixed effects regressions showed that, controlling for time-invariant user characteristics, mid and high tetrahydrocannabinol (THC) levels were the primary independent predictor of increased symptom relief, and that when broken out by symptom type, this effect was only statistically significant for our largest sample of users, those reporting anxiety rather than agitation/irritability or stress. Cannabidiol (CBD) levels were generally not associated with changes in symptom intensity levels. In a minority of cannabis use sessions (< 13%), cannabis users reported anxiogenic-related negative side effects (e.g., feeling anxious, irritable, paranoid, rapid pulse, or restless), whereas in a majority of sessions (about 66%), users reported positive anxiolytic side effects (e.g., feeling chill, comfy, happy, optimistic, peaceful, or relaxed).

CONCLUSIONS

The findings suggest the majority of patients in our sample experienced relief from distress-related symptoms following consumption of Cannabis flower, and that among product characteristics, higher THC levels were the strongest predictors of relief.

Antinociceptive and anxiolytic-like effects of a neo-clerodane diterpene from Salvia semiatrata aerial parts

CONTEXT

Salvia semiatrata Zucc. (Lamiaceae) is a species used as a tranquilizer and to relieve pain in folk medicine in Santiago Huauclilla, Oaxaca, Mexico.

OBJECTIVE

To evaluate the antinociceptive and anxiolytic-like effects of S. semiatrata extracts and identify a bioactive metabolite.

MATERIALS AND METHODS

The extracts were obtained by maceration of S. semiatrata aerial parts using solvents in increasing polarity (hexane, ethyl acetate and methanol). A neo-clerodane diterpene was extracted from the ethyl acetate fraction using open column chromatography. Identification of this metabolite was performed by crystallography, ¹H NMR, ¹³C NMR, ATR-IR, ECD, MS and elemental analysis. The antinociceptive activity was explored using the writhing and formalin tests. Whereas, the anxiolytic-like responses were analysed in the open-field, hole-board and plus-maze tests. All the treatments were administered using oral gavage in male CD1 mice and explored 30 min after administration of the individual extracts (300 mg/kg) or the compound 1 (0.1, 1 or 10 mg/kg).

RESULTS

All the extracts produced significant reduction in the nociceptive and anxiety-like behaviour compared to mice treated with the vehicle (0.5% tween 80 in saline solution). The spectroscopic analysis corroborated the presence of the neo-clerodane diterpene 7-keto-neoclerodan-3,13-dien-18,19:15,16-diolide (1), as partial responsible of the antinociceptive and anxiolytic-like effects, which produced a dose-dependent response in the writhing test with an ED₅₀=4.15 mg/kg. Discussion and conclusions: These results reinforce the medicinal properties of S. semiatrata in folk medicine, where participation of a neo-clerodane diterpene was evidenced in the inhibitory central nervous system activity of this species.

Role of Cannabinoid Receptors in Psychological Disorder

Cannabinoid receptors, located throughout the body, are part of the endocannabinoid system. Cannabinoid CB1 and CB2 receptors are G protein-coupled receptors present from the early stages of gestation, which is involved in various physiological processes, including appetite, pain-sensation, mood, and memory. Due to the lipophilic nature of cannabinoids, it was initially thought that these compounds exert several biological effects by disrupting the cell membrane nonspecifically. Recent biochemical and behavioral findings have demonstrated that blockade of CB1 receptors engenders antidepressant-like neurochemical changes (increases in extracellular levels of monoamines in cortical but not subcortical brain regions) and behavioral effects consistent with antidepressant/antistress activity. We aim to define various roles of cannabinoid receptors in modulating signaling pathways and association with several pathophysiological conditions.

Synthetic cannabinoid CP-55,940 induces apoptosis in a human skeletal muscle model via regulation of CB1 receptors and L-type Ca2+ channels

Rhabdomyolysis has been reported in patients who abuse synthetic cannabinoids. However, no studies have yet assessed whether these cases reflect the direct cytotoxicity of synthetic cannabinoids on skeletal muscle, a possibility that the present study sought to address. Specifically, this study investigated the cytotoxicity of the synthetic cannabinoid CP-55,940, a compound that acts equally on both types of cannabinoid receptors (CB₁ and CB₂), in a human embryonic rhabdomyosarcoma (RD) cell line. Exposure of these cells to CP-55,940 resulted in concentration-dependent decreases in cell viability. These effects were attenuated by pre-incubation with AM251 (30 µM), a selective CB₁ receptor antagonist, but not by pre-incubation with AM630 (30 µM), a selective CB₂ receptor antagonist. Following treatment with CP-55,940, RD cells exhibited apoptosis, as indicated by the accumulation of annexin-V, activation of caspase-3, and a loss of the mitochondrial membrane potential. Additionally, CP-55,940 treatment of RD cells led to increases in intracellular Ca²⁺ levels. CP-55,940-induced cell death was significantly attenuated in the absence of extracellular Ca²⁺, and was partially decreased by pre-incubation with verapamil (5 µM) or diltiazem (5 µM), compounds that block the L-type Ca²⁺ channel. Our results indicate that the cytotoxicity of CP-55,940 towards RD cells (skeletal muscle cells) is mediated by the CB₁ receptor, but not by the CB₂ receptor. Our results further suggest that calcium influx through the L-type channel may play an important role in the apoptosis induced by these compounds.

Cannabinoid Receptors: An Update on Cell Signaling, Pathophysiological Roles and Therapeutic Opportunities in Neurological, Cardiovascular, and Inflammatory Diseases

The identification of the human cannabinoid receptors and their roles in health and disease, has been one of the most significant biochemical and pharmacological advancements to have occurred in the past few decades. In spite of the major strides made in furthering endocannabinoid research, therapeutic exploitation of the endocannabinoid system has often been a challenging task. An impaired endocannabinoid tone often manifests as changes in expression and/or functions of type 1 and/or type 2 cannabinoid receptors. It becomes important to understand how alterations in cannabinoid receptor cellular signaling can lead to disruptions in major physiological and biological functions, as they are often associated with the pathogenesis of several neurological, cardiovascular, metabolic, and inflammatory diseases. This review focusses mostly on the pathophysiological roles of type 1 and type 2 cannabinoid receptors, and it attempts to integrate both cellular and physiological functions of the cannabinoid receptors. Apart from an updated review of pre-clinical and clinical studies, the adequacy/inadequacy of cannabinoid-based therapeutics in various pathological conditions is also highlighted. Finally, alternative strategies to modulate endocannabinoid tone, and future directions are also emphasized.

Kaempferol Facilitated Extinction Learning in Contextual Fear Conditioned Rats via Inhibition of Fatty-Acid Amide Hydrolase

Background: Fear, stress, and anxiety-like behaviors originate from traumatic events in life. Stress response is managed by endocannabinoids in the body by limiting the uncontrolled retrieval of aversive memories. Pharmacotherapy-modulating endocannabinoids, especially anandamide, presents a promising tool for treating anxiety disorders. Here, we investigated the effect of kaempferol, a flavonoid, in the extinction of fear related memories and associated anxiety-like behavior. Methods: The ability of kaempferol to inhibit fatty-acid amide hydrolase (FAAH, the enzyme that catabolizes anandamide) was assessed in vitro using an enzyme-linked immunosorbent assay (ELISA) kit. For animal studies (in vivo), the extinction learning was evaluated using contextual fear conditioning (CFC, a behavioral paradigm based on ability to learn and remember aversive stimuli). Furthermore, an elevated plus-maze (EPM) model was used for measuring anxiety-like behavior, while serum corticosterone served as a biochemical indicator of anxiety. Lastly, the interaction of kaempferol with FAAH enzyme was also assessed in silico (computational study). Results: Our data showed that kaempferol inhibited the FAAH enzyme with an IC₅₀ value of 1 µM. In CFC, it reduced freezing behavior in rats. EPM data demonstrated anxiolytic activity as exhibited by enhanced number of entries and time spent in the open arm. No change in blood corticosterone levels was noted. Our computational study showed that Kaempferol interacted with the catalytic amino acids (SER241, PHE192, PHE381, and THR377) of FAAH enzyme Conclusion: Our study demonstrate that kaempferol facilitated the extinction of aversive memories along with a reduction of anxiety. The effect is mediated through the augmentation of endocannabinoids via the inhibition of FAAH enzyme.

Cannabis, a cause for anxiety? A critical appraisal of the anxiogenic and anxiolytic properties

BACKGROUND

Cannabis has been documented for use in alleviating anxiety. However, certain research has also shown that it can produce feelings of anxiety, panic, paranoia and psychosis. In humans, Δ9-tetrahydrocannabinol (THC) has been associated with an anxiogenic response, while anxiolytic activity has been attributed mainly to cannabidiol (CBD). In animal studies, the effects of THC are highly dose-dependent, and biphasic effects of cannabinoids on anxiety-related responses have been extensively documented. A more precise assessment is required of both the anxiolytic and anxiogenic potentials of phytocannabinoids, with an aim towards the development of the 'holy grail' in cannabis research, a medicinally-active formulation which may assist in the treatment of anxiety or mood disorders without eliciting any anxiogenic effects.

OBJECTIVES

To systematically review studies assessing cannabinoid interventions (e.g. THC or CBD or whole cannabis interventions) both in animals and humans, as well as recent epidemiological studies reporting on anxiolytic or anxiogenic effects from cannabis consumption.

METHOD

The articles selected for this review were identified up to January 2020 through searches in the electronic databases OVID MEDLINE, Cochrane Central Register of Controlled Trials, PubMed, and PsycINFO.

RESULTS

Acute doses of CBD were found to reduce anxiety both in animals and humans, without having an anxiogenic effect at higher doses. Epidemiological studies tend to support an anxiolytic effect from the consumption of either  CBD or THC, as well as whole plant cannabis. Conversely, the available human clinical studies demonstrate a common anxiogenic response to THC (especially at higher doses).

CONCLUSION

Based on current data, cannabinoid therapies (containing primarily CBD) may provide a more suitable treatment for people with pre-existing anxiety or as a potential adjunctive role in managing anxiety or stress-related disorders. However, further research is needed to explore other cannabinoids and phytochemical constituents present in cannabis (e.g. terpenes) as anxiolytic interventions. Future clinical trials involving patients with anxiety disorders are warranted due to the small number of available human studies.

Effects of ∆9-tetrahydrocannabinol on aversive memories and anxiety: a review from human studies

BACKGROUND

Posttraumatic stress disorder (PTSD) may stem from the formation of aberrant and enduring aversive memories. Some PTSD patients have recreationally used Cannabis, probably aiming at relieving their symptomatology. However, it is still largely unknown whether and how Cannabis or its psychotomimetic compound Δ⁹-tetrahydrocannabinol (THC) attenuates the aversive/traumatic memory outcomes. Here, we seek to review and discuss the effects of THC on aversive memory extinction and anxiety in healthy humans and PTSD patients.

METHODS

Medline, PubMed, Cochrane Library, and Central Register for Controlled Trials databases were searched to identify peer-reviewed published studies and randomized controlled trials in humans published in English between 1974 and July 2020, including those using only THC and THC combined with cannabidiol (CBD). The effect size of the experimental intervention under investigation was calculated.

RESULTS

At low doses, THC can enhance the extinction rate and reduce anxiety responses. Both effects involve the activation of cannabinoid type-1 receptors in discrete components of the corticolimbic circuitry, which could couterbalance the low "endocannabinoid tonus" reported in PTSD patients. The advantage of associating CBD with THC to attenuate anxiety while minimizing the potential psychotic or anxiogenic effect produced by high doses of THC has been reported. The effects of THC either alone or combined with CBD on aversive memory reconsolidation, however, are still unknown.

CONCLUSIONS

Current evidence from healthy humans and PTSD patients supports the THC value to suppress anxiety and aversive memory expression without producing significant adverse effects if used in low doses or when associated with CBD. Future studies are guaranteed to address open questions related to their dose ratios, administration routes, pharmacokinetic interactions, sex-dependent differences, and prolonged efficacy.

Endocannabinoid System Components as Potential Biomarkers in Psychiatry

The high heterogeneity of psychiatric disorders leads to a lack of diagnostic precision. Therefore, the search of biomarkers is a fundamental aspect in psychiatry to reach a more personalized medicine. The endocannabinoid system (ECS) has gained increasing interest due to its involvement in many different functional processes in the brain, including the regulation of emotions, motivation, and cognition. This article reviews the role of the main components of the ECS as biomarkers in certain psychiatric disorders. Studies carried out in rodents evaluating the effects of pharmacological and genetic manipulation of cannabinoid receptors or endocannabinoids (eCBs) degrading enzymes were included. Likewise, the ECS-related alterations occurring at the molecular level in animal models reproducing some behavioral and/or neuropathological aspects of psychiatric disorders were reviewed. Furthermore, clinical studies evaluating gene or protein alterations in post-mortem brain tissue or in vivo blood, plasma, and cerebrospinal fluid (CSF) samples were analyzed. Also, the results from neuroimaging studies using positron emission tomography (PET) or functional magnetic resonance (fMRI) were included. This review shows the close involvement of cannabinoid receptor 1 (CB1r) in stress regulation and the development of mood disorders [anxiety, depression, bipolar disorder (BD)], in post-traumatic stress disorder (PTSD), as well as in the etiopathogenesis of schizophrenia, attention deficit hyperactivity disorder (ADHD), or eating disorders (i.e. anorexia and bulimia nervosa). On the other hand, recent results reveal the potential therapeutic action of the endocannabinoid tone manipulation by inhibition of eCBs degrading enzymes, as well as by the modulation of cannabinoid receptor 2 (CB2r) activity on anxiolytic, antidepressive, or antipsychotic associated effects. Further clinical research studies are needed; however, current evidence suggests that the components of the ECS may become promising biomarkers in psychiatry to improve, at least in part, the diagnosis and pharmacological treatment of psychiatric disorders.

Effects of the synthetic cannabinoid 5F-AMB on anxiety and recognition memory in mice

RATIONALE

N-[[1-(5-fluoropentyl)-1H-indazol-3-yl]carbonyl]-L-valine methyl ester (5F-AMB) is a synthetic cannabinoid that has been distributed recently. Although inhalation of 5F-AMB produces adverse effects, such as impaired memory and disturbed consciousness, in humans, the psychopharmacological effects of 5F-AMB in rodents have not been investigated.

OBJECTIVES

We first examined the effects of intraperitoneal and intracerebroventricular injections of 5F-AMB on anxiety-like behavior and locomotor activity in the open field (OF) test and recognition memory in the novel object recognition test (NOR) in C57BL/6J mice. We also examined whether a cannabinoid 1 (CB1) receptor antagonist AM251 blocks the effects of 5F-AMB. We next examined the effects of 5F-AMB infusion into the medial prefrontal cortex (mPFC), a brain region associated with anxiety and memory, on these tests.

RESULTS

Intraperitoneal injection of 5F-AMB (0.3 mg/kg) dramatically decreased locomotor activity in the OF, and this effect was partially reversed by AM251 (3 mg/kg). Intracerebroventricular infusion of 5F-AMB (10 nmol) produced an anxiolytic effect in the OF and impaired acquisition, but not retrieval, of recognition memory in the NOR, and these effects were blocked by co-infusion of AM251 (1.8 nmol). Bilateral intra-mPFC infusion of 5F-AMB (10 pmol/side) similarly produced impaired recognition memory acquisition, but no anxiolytic effect.

CONCLUSIONS

The results demonstrate that centrally administered 5F-AMB produces anxiolytic effect and impaired recognition memory acquisition via activation of CB1 receptors, while systemic 5F-AMB severely impaired locomotor activity. The mPFC is involved in 5F-AMB-induced impairment of recognition memory acquisition. However, other brain region(s) may contribute to the 5F-AMB-induced anxiolytic effect.

Joint effects of stress and chronic cannabis use on prospective memory

RATIONALE

Prospective memory pervades our daily lives and failures can have detrimental consequences. This ability to execute delayed intentions may be impacted by stress, yet few studies have examined these effects. Moreover, as many cannabis users report using cannabis to cope with stress, it is important to understand how stress impacts memory in cannabis users.

OBJECTIVES

We assessed the effects of acute and chronic stress on prospective memory to examine whether stress differentially impacts prospective memory in cannabis users vs. non-users.

METHODS

Forty cannabis users and 42 non-users were assigned an episodic and a habitual prospective memory test before completing either the stress or no stress condition of the Maastricht Acute Stress Test (MAST). Participants were instructed to execute the habitual test during the MAST and the episodic test shortly after the MAST. Chronic stress was measured using the Perceived Stress Scale, and acute stress was measured using subjective ratings and cortisol.

RESULTS

There was a main effect of acute stress indicating that stress detrimentally impacted habitual prospective memory performance. Although there was not a significant stress x cannabis interaction, further planned comparisons indicated the habitual prospective memory impairment was selective to cannabis users. There were also significant negative correlations between (i) episodic prospective memory and both subjective stress as well as chronic stress, and (ii) habitual prospective memory and change in subjective stress.

CONCLUSIONS

This study is the first to reveal detrimental effects of acute stress on prospective memory performance, which may be exacerbated in cannabis users.

Δ-9-Tetrahydrocannabinol and Cannabidiol produce dissociable effects on prefrontal cortical executive function and regulation of affective behaviors

The use of cannabis for therapeutic and recreational purposes is growing exponentially. Nevertheless, substantial questions remain concerning the potential cognitive and affective side-effects associated with cannabis exposure. In particular, the effects of specific marijuana-derived phytocannabinoids on neural regions such as the prefrontal cortex (PFC) are of concern, given the role of the PFC in both executive cognitive function and affective processing. The main biologically active phytocannabinoids, ∆-9-tetrahydrocannabinol (THC) and cannabidiol (CBD), interact with multiple neurotransmitter systems important for these processes directly within the PFC. Considerable evidence has demonstrated that acute or chronic THC exposure may induce psychotomimetic effects, whereas CBD has been shown to produce potentially therapeutic effects for both psychosis and/or anxiety-related symptoms. Using an integrative combination of cognitive and affective behavioral pharmacological assays in rats, we report that acute intra-PFC infusions of THC produce anxiogenic effects while producing no impairments in executive function. In contrast, acute infusions of intra-PFC CBD impaired attentional set-shifting and spatial working memory, without interfering with anxiety or sociability behaviors. In contrast, intra-PFC CBD reversed the cognitive impairments induced by acute glutamatergic antagonism within the PFC, and blocked the anxiogenic properties of THC, suggesting that the therapeutic properties of CBD within the PFC may be present only during pathologically aberrant states within the PFC. Interestingly, the effects of PFC THC vs. CBD were found to be mediated through dissociable CB1 vs. 5-HT_1A-dependent receptor signaling mechanisms, directly in the PFC.

Integrating endocannabinoid signaling in the regulation of anxiety and depression

Brain endogenous cannabinoid (eCB) signaling seems to harmonize appropriate behavioral responses, which are essential for the organism's long-term viability and homeostasis. Dysregulation of eCB signaling contributes to negative emotional states and increased stress responses. An understanding of the underlying neural cell populations and neural circuit regulation will enable the development of therapeutic strategies to mitigate behavioral maladaptation and provide insight into the influence of eCB on the neural circuits involved in anxiety and depression. This review focuses on recent evidence that has added a new layer of complexity to the idea of targeting the eCB system for therapeutic benefits in neuropsychiatric disease and on the future research direction of neural circuit modulation.

New Perspectives on the Use of Cannabis in the Treatment of Psychiatric Disorders

Following the discovery of the endocannabinoid system and its potential as a therapeutic target for various pathological conditions, growing interest led researchers to investigate the role of cannabis and its derivatives for medical purposes. The compounds Δ9-tetrahydrocannabinol and cannabidiol are the most abundant phytocannabinoids found in cannabis extracts, as well as the most studied. The present review aims to provide an overview of the current evidence for their beneficial effects in treating psychiatric disorders, including schizophrenia, anxiety, and depression. Nevertheless, further investigations are required to clarify many pending issues, especially those relative to the assessment of benefits and risks when using cannabis for therapeutic purposes, thereby also helping national and federal jurisdictions to remain updated.

Zebrafish models relevant to studying central opioid and endocannabinoid systems

The endocannabinoid and opioid systems are two interplaying neurotransmitter systems that modulate drug abuse, anxiety, pain, cognition, neurogenesis and immune activity. Although they are involved in such critical functions, our understanding of endocannabinoid and opioid physiology remains limited, necessitating further studies, novel models and new model organisms in this field. Zebrafish (Danio rerio) is rapidly emerging as one of the most effective translational models in neuroscience and biological psychiatry. Due to their high physiological and genetic homology to humans, zebrafish may be effectively used to study the endocannabinoid and opioid systems. Here, we discuss current models used to target the endocannabinoid and opioid systems in zebrafish, and their potential use in future translational research and high-throughput drug screening. Emphasizing the high degree of conservation of the endocannabinoid and opioid systems in zebrafish and mammals, we suggest zebrafish as an excellent model organism to study these systems and to search for the new drugs and therapies targeting their evolutionarily conserved mechanisms.

Bidirectional influence of amygdala β1-adrenoceptors blockade on cannabinoid signaling in contextual and auditory fear memory

The basolateral amygdala (BLA) is a major target and modulator of stress and has a critical role in the neural circuitry presenting learned fear behaviors. On the other hand, both the endocannabinoid and noradrenergic systems may be involved in regulating the stress responses, fear, and anxiety. Considering the aforementioned, we have investigated the involvement of the BLA β₁-adrenoceptors in conditioned fear responses induced by ACPA, a CB1 receptor (CB1R) agonist. In adult male NMRI mice, freezing responses to context and cue were measured using a Pavlovian fear conditioning apparatus. Pre-training intra-BLA microinjection of xamoterol (0.01 and 0.02 µg/mouse), a partial β₁-adrenoceptor agonist, or atenolol (0.5 µg/mouse), a β₁-adrenoceptor antagonist, decreased freezing behavior, which suggests an impairment of contextual and auditory fear retrieval. Similar results were found with pre-training intraperitoneal administration of ACPA (0.5 mg/kg). A sub-threshold dose of xamoterol, infused into the BLA, decreased ACPA (0.005 and 0.05 mg/kg) effect on both memories, while atenolol increased ACPA response to the context at the middle dose and decreased ACPA response to the tone at the lower dose. It can be concluded that the blockade of BLA β₁-adrenoceptors differentially affects ACPA response on the contextual and auditory conditioned fear memories.

Sex-specific effects of CB1 receptor antagonism and stress in adolescence on anxiety, corticosterone concentrations, and contextual fear in adulthood in rats

There is a paucity of research regarding the role of endogenous cannabinoid signalling in adolescence on brain and behaviour development. We previously demonstrated effects of repeated CB1 receptor antagonism in adolescence on socioemotional behaviours and neural protein expression 24-48 h after the last drug administration in female rats, with no effect in males. Here we investigate whether greater effects would be manifested after a lengthier delay. In Experiment 1, male and female rats were administered either 1 mg / kg of the CB1 receptor-selective antagonist AM251, vehicle (VEH), or did not receive injections (NoINJ) daily on postnatal days (PND) 30-44 either alone (no adolescent confinement stress; noACS), or in tandem with 1 h ACS. On PND 70, adolescent AM251 exposure reduced anxiety in an elevated plus maze in males, irrespective of ACS, with no effects in females. On PND 73, there were no group differences in either sex in plasma corticosterone concentrations before or after 30 min of restraint stress, although injection stress resulted in higher baseline concentrations in males. Brains were collected on PND 74, with negligible effects of either AM251 or ACS on protein markers of synaptic plasticity and of the endocannabinoid system in the hippocampus and medial prefrontal cortex. In Experiment 2, rats from both sexes were treated with vehicle or AM251 on PND 30-44 and were tested for contextual fear conditioning and extinction in adulthood. AM251 females had greater fear recall than VEH females 24 h after conditioning, with no group differences in within- or between-session fear extinction. There were no group differences in long-term extinction memory, although AM251 females froze more during a reconditioning trial compared with VEH females. There were no group differences on any of the fear conditioning measures in males. Together, these findings indicate a modest, sex-specific role of CB1 receptor signalling in adolescence on anxiety-like behaviour in males and conditioned fear behaviour in females.

Prefrontal endocannabinoids, stress controllability and resilience: A hypothesis

Stressor exposure is a predisposing risk factor for many psychiatric conditions such as PTSD and depression. However, stressors do not influence all individuals equally and in response to an identical stressor some individuals may be vulnerable while others are resilient. While various biological and behavioral factors contribute to vulnerability versus resilience, an individual's degree of control over the stressor is among the most potent. Even with only one experience with control over stress, behavioral control has been shown to have acute and long-lasting stress-mitigating effects. This suggests that control both blunts the response to acute stress and prepares the subject to be resilient to future stressors. In this review, we first summarize the evidence which suggests the ventromedial prefrontal cortex (vmPFC) is a critical component of stressor controllability circuits and a locus of neuroplasticity supporting the acute and long-lasting consequences of control. We next review the central endocannabinoid (eCB) system as a possible mediator of short and long-term synaptic transmission in the vmPFC, and offer a hypothesis whereby eCBs regulate vmPFC circuits engaged when a subject has control over stress and may contribute to the encoding of acute stress coping into long lasting stressor resilience.