The Endocannabinoid System and Anxiety

Sexually dimorphic effects of monoacylglycerol lipase inhibitor MJN110 on stress-related behaviour and drinking in Marchigian Sardinian alcohol-preferring rats

BACKGROUND AND PURPOSE

The endocannabinoid (eCB) system plays an important homeostatic role in the regulation of stress circuits and has emerged as a therapeutic target to treat stress disorders and alcohol use disorder (AUD). Extensive research has elucidated a role for the eCB anandamide (AEA), but less is known about 2-arachidonoylglycerol (2-AG) mediated signalling.

EXPERIMENTAL APPROACH

We pharmacologically enhanced eCB signalling by inhibiting the 2-AG metabolizing enzyme, monoacylglycerol lipase (MAGL), in male and female Marchigian Sardinian alcohol-preferring (msP) rats, a model of innate alcohol preference and stress hypersensitivity, and in control Wistar rats. We tested the acute effect of the selective MAGL inhibitor MJN110 in alleviating symptoms of alcohol drinking, anxiety, irritability and fear.

KEY RESULTS

A single systemic administration of MJN110 increased 2-AG levels in the central amygdala, prelimbic and infralimbic cortex but did not acutely alter alcohol drinking. MAGL inhibition reduced aggressive behaviours in female msPs, and increased defensive behaviours in male msPs, during the irritability test. Moreover, in the novelty-induced hypophagia test, MJN110 selectively enhanced palatable food consumption in females, mitigating stress-induced food suppression. Lastly, msP rats showed increased conditioned fear behaviour compared with Wistar rats, and MJN110 reduced context-associated conditioned fear responses, but not cue-probed fear expression, in male msPs.

CONCLUSIONS AND IMPLICATIONS

Acute inhibition of MAGL attenuated some stress-related responses in msP rats but not voluntary alcohol drinking. Our results provide new insights into the sex dimorphism documented in stress-induced responses. Sex-specific eCB-based approaches should be considered in the clinical development of therapeutics.

Perturbation of 3D nuclear architecture, epigenomic aging and dysregulation, and cannabinoid synaptopathy reconfigures conceptualization of cannabinoid pathophysiology: part 2-Metabolome, immunome, synaptome

The second part of this paper builds upon and expands the epigenomic-aging perspective presented in Part 1 to describe the metabolomic and immunomic bases of the epigenomic-aging changes and then considers in some detail the application of these insights to neurotoxicity, neuronal epigenotoxicity, and synaptopathy. Cannabinoids are well-known to have bidirectional immunomodulatory activities on numerous parts of the immune system. Immune perturbations are well-known to impact the aging process, the epigenome, and intermediate metabolism. Cannabinoids also impact metabolism via many pathways. Metabolism directly impacts immune, genetic, and epigenetic processes. Synaptic activity, synaptic pruning, and, thus, the sculpting of neural circuits are based upon metabolic, immune, and epigenomic networks at the synapse, around the synapse, and in the cell body. Many neuropsychiatric disorders including depression, anxiety, schizophrenia, bipolar affective disorder, and autistic spectrum disorder have been linked with cannabis. Therefore, it is important to consider these features and their complex interrelationships in reaching a comprehensive understanding of cannabinoid dependence. Together these findings indicate that cannabinoid perturbations of the immunome and metabolome are important to consider alongside the well-recognized genomic and epigenomic perturbations and it is important to understand their interdependence and interconnectedness in reaching a comprehensive appreciation of the true nature of cannabinoid pathophysiology. For these reasons, a comprehensive appreciation of cannabinoid pathophysiology necessitates a coordinated multiomics investigation of cannabinoid genome-epigenome-transcriptome-metabolome-immunome, chromatin conformation, and 3D nuclear architecture which therefore form the proper mechanistic underpinning for major new and concerning epidemiological findings relating to cannabis exposure.

Perturbation of 3D nuclear architecture, epigenomic dysregulation and aging, and cannabinoid synaptopathy reconfigures conceptualization of cannabinoid pathophysiology: part 1-aging and epigenomics

Much recent attention has been directed toward the spatial organization of the cell nucleus and the manner in which three-dimensional topologically associated domains and transcription factories are epigenetically coordinated to precisely bring enhancers into close proximity with promoters to control gene expression. Twenty lines of evidence robustly implicate cannabinoid exposure with accelerated organismal and cellular aging. Aging has recently been shown to be caused by increased DNA breaks. These breaks rearrange and maldistribute the epigenomic machinery to weaken and reverse cellular differentiation, cause genome-wide DNA demethylation, reduce gene transcription, and lead to the inhibition of developmental pathways, which contribute to the progressive loss of function and chronic immune stimulation that characterize cellular aging. Both cell lineage-defining superenhancers and the superanchors that control them are weakened. Cannabis exposure phenocopies the elements of this process and reproduces DNA and chromatin breakages, reduces the DNA, RNA protein and histone synthesis, interferes with the epigenomic machinery controlling both DNA and histone modifications, induces general DNA hypomethylation, and epigenomically disrupts both the critical boundary elements and the cohesin motors that create chromatin loops. This pattern of widespread interference with developmental programs and relative cellular dedifferentiation (which is pro-oncogenic) is reinforced by cannabinoid impairment of intermediate metabolism (which locks in the stem cell-like hyper-replicative state) and cannabinoid immune stimulation (which perpetuates and increases aging and senescence programs, DNA damage, DNA hypomethylation, genomic instability, and oncogenesis), which together account for the diverse pattern of teratologic and carcinogenic outcomes reported in recent large epidemiologic studies in Europe, the USA, and elsewhere. It also accounts for the prominent aging phenotype observed clinically in long-term cannabis use disorder and the 20 characteristics of aging that it manifests. Increasing daily cannabis use, increasing use in pregnancy, and exponential dose-response effects heighten the epidemiologic and clinical urgency of these findings. Together, these findings indicate that cannabinoid genotoxicity and epigenotoxicity are prominent features of cannabis dependence and strongly indicate coordinated multiomics investigations of cannabinoid genome-epigenome-transcriptome-metabolome, chromatin conformation, and 3D nuclear architecture. Considering the well-established exponential dose-response relationships, the diversity of cannabinoids, and the multigenerational nature of the implications, great caution is warranted in community cannabinoid penetration.

Anxiety associated with palatable food withdrawal is reversed by the selective FAAH inhibitor PF-3845: A regional analysis of the contribution of endocannabinoid signaling machinery

OBJECTIVE

Consumption of energy-dense palatable "comfort" food can alleviate stress and negative emotions, while abrupt withdrawal from a palatable diet can worsen these symptoms, causing difficulties with adherence to weight-loss diets. Currently, no pharmacological treatment is effective for obesity-related anxiety, so we investigated the endocannabinoid system (ECS), and specifically the fatty acid amide hydrolase (FAAH), as an interesting emerging target in this context because of its key role in the regulation of both energy homeostasis and emotional behavior.

METHODS

Rats were subjected to exposure and subsequent abstinence from a palatable cafeteria diet. During abstinence period, rats were treated with the selective FAAH inhibitor PF-3845 (10 mg/kg; intraperitoneal administration every other day).

RESULTS

Abstinent rats displayed an anxiogenic-like behavior and changes in the proteins of ECS signaling machinery in brain areas involved both in anxiety and food intake regulation. In particular, withdrawal caused a reduction of the expression of cannabinoid receptors in the nucleus accumbens and of enzymes diacylglycerol lipase alpha and monoacylglycerol lipase (MAGL) in the amygdala. Pharmacological inhibition of FAAH exerted an anxiolytic-like effect in abstinent animals and increased both MAGL expression in amygdala and CB2 expression in prefrontal cortex.

DISCUSSION

Overall, our results suggest that emotional disturbances associated with dieting are coupled with region-specific alterations in the cerebral expression of the ECS and that the enhancement of the endocannabinoid signaling by FAAH inhibition might represent a novel pharmacological strategy for the treatment of anxiety related to abstinence from palatable food.

PUBLIC SIGNIFICANCE

The present study focused on evaluating the role of the endocannabinoid system in modulating withdrawal from naturally rewarding activities that have an impact on mood, such as feeding. The variations observed in the emotional behavior of abstinent rats was linked to neuroadaptations of the ECS in specific brain areas.

Clinical Epigenomic Explanation of the Epidemiology of Cannabinoid Genotoxicity Manifesting as Transgenerational Teratogenesis, Cancerogenesis and Aging Acceleration

As global interest in the therapeutic potential of cannabis and its' derivatives for the management of selected diseases increases, it is increasingly imperative that the toxic profile of cannabinoids be thoroughly understood in order to correctly assess the balance between the therapeutic risks and benefits. Modern studies across a number of jurisdictions, including Canada, Australia, the US and Europe have confirmed that some of the most worrying and severe historical reports of both congenital anomalies and cancer induction following cannabis exposure actually underestimate the multisystem thousand megabase-scale transgenerational genetic damage. These findings from teratogenic and carcinogenic literature are supported by recent data showing the accelerated patterns of chronic disease and the advanced DNA methylation epigenomic clock age in cannabis exposed patients. Together, the increased multisystem carcinogenesis, teratogenesis and accelerated aging point strongly to cannabinoid-related genotoxicity being much more clinically significant than it is widely supposed and, thus, of very considerable public health and multigenerational impact. Recently reported longitudinal epigenome-wide association studies elegantly explain many of these observed effects with considerable methodological sophistication, including multiple pathways for the inhibition of the normal chromosomal segregation and DNA repair, the inhibition of the basic epigenetic machinery for DNA methylation and the demethylation and telomerase acceleration of the epigenomic promoter hypermethylation characterizing aging. For cancer, 810 hits were also noted. The types of malignancy which were observed have all been documented epidemiologically. Detailed epigenomic explications of the brain, heart, face, uronephrological, gastrointestinal and limb development were provided, which amply explained the observed teratological patterns, including the inhibition of the key morphogenic gradients. Hence, these major epigenomic insights constituted a powerful new series of arguments which advanced both our understanding of the downstream sequalae of multisystem multigenerational cannabinoid genotoxicity and also, since mechanisms are key to the causal argument, inveighed strongly in favor of the causal nature of the relationship. In this introductory conceptual overview, we present the various aspects of this novel synthetic paradigmatic framework. Such concepts suggest and, indeed, indicate numerous fields for further investigation and basic science research to advance the exploration of many important issues in biology, clinical medicine and population health. Given this, it is imperative we correctly appraise the risk-benefit ratio for each potential cannabis application, considering the potency, severity of disease, stage of human development and duration of use.

Cannabinoids to Improve Health-Related Quality of Life in Patients with Neurological or Oncological Disease: A Meta-Analysis

Background: Cannabinoids have been suggested to alleviate frequently experienced symptoms of reduced mental well-being such as anxiety and depression. Mental well-being is an important subdomain of health-related quality of life (HRQoL). Reducing symptoms and maintaining HRQoL are particularly important in malignant primary brain tumor patients, as treatment options are often noncurative and prognosis remains poor. These patients frequently report unprescribed cannabinoid use, presumably for symptom relieve. As studies on brain tumor patients specifically are lacking, we performed a meta-analysis of the current evidence on cannabinoid efficacy on HRQoL and mental well-being in oncological and neurological patients. Methods: We performed a systematic PubMed, PsychINFO, Embase, and Web of Science search according to PRISMA guidelines on August 2 and 3, 2021. We included randomized controlled trials (RCTs) that assessed the effects of tetrahydrocannabinol (THC) or cannabidiol (CBD) on general HRQoL and mental well-being. Pooled effect sizes were calculated using Hedges g. Risk of bias of included studies was assessed using Cochrane's Risk of Bias tool. Results: We included 17 studies: 4 in oncology and 13 in central nervous system (CNS) disease. Meta-analysis showed no effect of cannabinoids on general HRQoL (g=-0.02 confidence interval [95% CI -0.11 to 0.06]; p=0.57) or mental well-being (g=-0.02 [95% CI -0.16 to 0.13]; p=0.81). Conclusions: RCTs in patients with cancer or CNS disease showed no effect of cannabinoids on HRQoL or mental well-being. However, studies were clinically heterogeneous and since many glioma patients currently frequently use cannabinoids, future studies are necessary to evaluate its value in this specific population.

Sex-dependent differences in the anxiolytic-like effect of cannabidiol in the elevated plus-maze

RATIONALE

Cannabidiol (CBD), the major non-psychoactive constituent of cannabis, has therapeutic potential for the treatment of anxiety. Most preclinical studies investigate only acute effects of CBD and only in males, yet the drug is most likely to be used over a sustained period in clinical practice.

OBJECTIVES

The objectives of this study were to investigate the anxiolytic-like effect of CBD in female rats compared to males and to determine whether the responsiveness of females was influenced by the stage of the estrous cycle.

METHODS

We carried out experiments to compare the effect of CBD in male and female rats in the elevated plus maze (EPM) in response to acute and short-term (4 days) administration through a complete cycle in females.

RESULTS

Male and female rats behaved in a similar manner in the EPM, but females in the late diestrus (LD) phase exhibited more anxiety-like behavior than at other stages, the difference reaching statistical significance compared to proestrus stages. CBD produced anxiolytic-like effects in both sexes, but female rats were responsive only in LD and 10-fold lower dose than males. After sub-chronic (4 days) treatment, responsiveness to CBD was maintained in females in LD, but females in proestrus remained unresponsive to CBD treatment.

CONCLUSIONS

We suggest that there are sex differences in the anxiolytic-like effects of CBD in rats that reflect different underlying mechanisms: based on literature data, gonadal hormone status linked to GABA_A receptor expression in females, and 5-HT_1A receptor activation in males.

Effects of ayahuasca on the endocannabinoid system of healthy volunteers and in volunteers with social anxiety disorder: Results from two pilot, proof-of-concept, randomized, placebo-controlled trials

OBJECTIVE

To assess endocannabinoid (anandamide, AEA; 2-arachidonoylglycerol, 2-AG) plasma levels in healthy volunteers and in volunteers with social anxiety disorder (SAD) after a single oral dose of ayahuasca or placebo.

METHODS

Post hoc analysis of endocannabinoid plasma levels (baseline, 90 and 240 min after drug intake) from two parallel-group, randomized, placebo-controlled trials. In Study 1, 20 healthy volunteers ingested ayahuasca (average 1.58 mg/ml dimethyltryptamine (DMT)) or placebo, and in Study 2, 17 volunteers with SAD received ayahuasca (average 0.680 mg/ml DMT) or placebo.

RESULTS

A significant difference was observed in AEA concentrations in Study 2 after ayahuasca intake (Χ² (2) = 6.5, p = 0.03, Friedman test), and near significant differences (increases) were observed between baseline and 90 (Z = 0, p = 0.06, Wilcoxon test) and 240 (Z = 10, p = 0.06) minutes after ayahuasca intake.

CONCLUSIONS

Although our findings suggest that ayahuasca could modulate AEA levels in SAD patients, the high interindividual variability in both trials and the small samples preclude definitive conclusions. More research with larger samples is needed to better understand the effects of ayahuasca and other hallucinogens in the endocannabinoid system.

Cannabinoid CB1 Receptor Involvement in the Actions of CBD on Anxiety and Coping Behaviors in Mice

The anxiolytic and antidepressant properties of cannabidiol (CBD) have been evaluated in several studies. However, the molecular mechanisms involved in these actions remain unclear. A total of 130 male mice were used. CBD’s ability to modulate emotional disturbances (anxiety and depressive-like behaviors) was evaluated at different doses in wild-type (CD1; 10, 20 and 30 mg/kg; i.p.) and knockout (CB1KO, CB2KO; GPR55KO; 20 mg/kg) mice. Moreover, CBD effects (20 mg/kg; i.p.) were evaluated in mice previously treated with the CB1r-antagonist SR141716A (2mg/kg; i.p.). Relative gene expression analyses of Cnr1 and Cnr2, Gpr55 and GABA(A)α2 and γ2 receptor subunits were performed in the amygdala (AMY) and hippocampus (HIPP) of CD1 mice. CBD (10 and 20 mg/kg) showed anxiolytic and antidepressant actions in CD1 mice, being more effective at 20 mg/kg. Its administration did not induce anxiolytic actions in CB1KO mice, contrary to CB2KO and GPR55KO. In all of them, the lack of cannabinoid receptors did not modify the antidepressant activity of CBD. Interestingly, the administration of the CB1r antagonist SR141716A blocked the anxiolytic-like activity of CBD. Real-time PCR studies revealed a significant reduction in Cnr1 and GABA(A)α2 and γ2 gene expression in the HIPP and AMY of CD1 mice treated with CBD. Opposite changes were observed in the Cnr2. Indeed, Gpr55 was increased in the AMY and reduced in the HIPP. CB1r appears to play a relevant role in modulating the anxiolytic actions of CBD. Moreover, this study revealed that CBD also modified the gene expression of GABA(A) subunits α2 and γ2 and CB1r, CB2r and GPR55, in a dose- and brain-region-dependent manner, supporting a multimodal mechanism of action for CBD.

Anti-aversive effect of 2-arachidonoylglycerol in the dorsolateral periaqueductal gray of male rats in contextual fear conditioning and Vogel tests

The endocannabinoid system modulates the stress coping strategies in the dorsolateral periaqueductal grey (dlPAG). The most relevant endocannabinoids, anandamide and 2-arachidonoylglycerol (2-AG) exert inhibitory control over defensive reactions mediated by the dlPAG. However, the protective role of anandamide is limited by its lack of effect in higher concentrations. Thus, the 2-AG emerges as a complementary target for developing new anxiolytic compounds. Nevertheless, the role of 2-AG on stress responsivity may vary according to the nature of the stimulus. In this study, we verified whether the dlPAG injection of 2-AG or inhibitors of its hydrolysis induce anxiolytic-like effects in male Wistar rats exposed to behavioral models in which physical stress (mild electric shock) is a critical component, namely the contextual fear conditioning test (CFC) and the Vogel conflict test (VCT). We also investigated the contribution of cannabinoid receptor type 1 (CB1) and type 2 (CB2) in such effects. The facilitation of 2-AG signaling in the dlPAG reduced contextual fear expression and exhibited an anxiolytic-like effect in the VCT in a mechanism dependent on activation of CB1 and CB2. However, the VCT required a higher dose than CFC. Further, the monoacylglycerol inhibitors, which inhibit the hydrolysis of 2-AG, were effective only in the CFC. In conclusion, we confirmed the anti-aversive properties of 2-AG in the dlPAG through CB1 and CB2 mechanisms. However, these effects could vary according to the type of stressor and the anxiety model employed.

Mental health and quality of life in a population of recreative cannabis users in Brazil

Cannabis is the third most used recreational drug worldwide. Despite the popularity of cannabis use among Brazilians, information about frequent cannabis users outside clinical contexts remains scarce. This is a cross-sectional study of a non-probabilistic sample of 7405 Brazilian adults (6620 [89.4%] cannabis users and 785 [10.6%] non-users) who answered an online survey that collected demographic data, cannabis and other substance use information (initial substance use, lifetime and past-month use), and standardized scales to assess quality of life, subjective well-being, anxiety, and depression scores. Among cannabis users, 17.1% of the participants self-classified themselves as occasional users, 64.6% as habitual users, and 7.7% as dysfunctional users. Participants were mostly young male adults, with at least high-school education, employed, without children. The highest scores for quality of life were observed among habitual cannabis users, followed by occasional users, while both non-users and dysfunctional users presented less favorable scores. Subjective measures of well-being were higher among habitual and occasional users than among non-users, whereas dysfunctional users were the most affected. Poor quality of life, depression or anxiety were more prevalent among dysfunctional users, but non-users of cannabis reported more depression or anxiety symptoms and less quality of life than both occasional and habitual users. The results obtained in this study are particularly relevant because they refer to a sample predominantly composed of habitual cannabis users from the general population, a rarely represented group in other surveys. The fact that cannabis use is generally associated with increased risk of adverse health outcomes was not observed in this study.

Local Anesthetic Efficacy in Marijuana Users and Nonusers: A Pilot Study

OBJECTIVE

Despite the common clinical impression that patients with a history of drug use are challenging to anesthetize with local anesthesia, literature on this clinical phenomenon is sparse. The objective of this pilot study was to assess if differences in local anesthetic efficacy for dental treatment exist between marijuana users and nonusers.

METHODS

Subjects were healthy adult males and females who qualified as either chronic marijuana users or nonusers. All subjects had an asymptomatic, vital maxillary lateral incisor that responded to an electric pulp test (EPT). A standard maxillary infiltration injection technique was employed using 1.7 mL 2% lidocaine with 1:100,000 epinephrine over the test tooth, and the tooth was tested with an EPT at 3-minute intervals.

RESULTS

A total of 88% of nonusers (15/17) and 61% of users (11/18) were successfully anesthetized, defined as anesthesia onset within 10 minutes and lasting at least 15 minutes. The difference in the proportion of anesthetized subjects was not statistically significant (P = .073). For subjects with successful anesthesia, there was no significant difference between nonusers and users in the onset or duration of anesthesia.

CONCLUSION

No significant differences in local anesthetic efficacy with respect to local anesthetic success, onset, or duration of action were found between chronic marijuana users and nonusers. However, larger studies are likely needed to provide more definitive evidence.

A review of the effects of acute and chronic cannabinoid exposure on the stress response

While cannabis has been used for centuries for its stress-alleviating properties, the effects of acute and chronic cannabinoid exposure on responses to stress remain poorly understood. This review provides an overview of studies that measured stress-related endpoints following acute or chronic cannabinoid exposure in humans and animals. Acute cannabinoid exposure increases basal concentrations of stress hormones in rodents and humans and has dose-dependent effects on stress reactivity in humans and anxiety-like behavior in rodents. Chronic cannabis exposure is associated with dampened stress reactivity, a blunted cortisol awakening response (CAR), and flattened diurnal cortisol slope in humans. Sex differences in these effects remain underexamined, with limited evidence for sex differences in effects of cannabinoids on stress reactivity in rodents. Future research is needed to better understand sex differences in the effects of cannabis on the stress response, as well as downstream impacts on mental health and stress-related disorders.

HPA Axis in the Pathomechanism of Depression and Schizophrenia: New Therapeutic Strategies Based on Its Participation

The hypothalamic-pituitary-adrenal (HPA) axis is involved in the pathophysiology of many neuropsychiatric disorders. Increased HPA axis activity can be observed during chronic stress, which plays a key role in the pathophysiology of depression. Overactivity of the HPA axis occurs in major depressive disorder (MDD), leading to cognitive dysfunction and reduced mood. There is also a correlation between the HPA axis activation and gut microbiota, which has a significant impact on the development of MDD. It is believed that the gut microbiota can influence the HPA axis function through the activity of cytokines, prostaglandins, or bacterial antigens of various microbial species. The activity of the HPA axis in schizophrenia varies and depends mainly on the severity of the disease. This review summarizes the involvement of the HPA axis in the pathogenesis of neuropsychiatric disorders, focusing on major depression and schizophrenia, and highlights a possible correlation between these conditions. Although many effective antidepressants are available, a large proportion of patients do not respond to initial treatment. This review also discusses new therapeutic strategies that affect the HPA axis, such as glucocorticoid receptor (GR) antagonists, vasopressin V1B receptor antagonists and non-psychoactive CB1 receptor agonists in depression and/or schizophrenia.

Microglial Cannabinoid Type 1 Receptor Regulates Brain Inflammation in a Sex-Specific Manner

Background: Neuroinflammation is a key feature shared by most, if not all, neuropathologies. It involves complex biological processes that act as a protective mechanism to fight against the injurious stimuli, but it can lead to tissue damage if self-perpetuating. In this context, microglia, the main cellular actor of neuroinflammation in the brain, are seen as a double-edged sword. By phagocyting neuronal debris, these cells can not only provide tissue repair but can also contribute to neuronal damage by releasing harmful substances, including inflammatory cytokines. The mechanisms guiding these apparent opposing actions are poorly known. The endocannabinoid system modulates the release of inflammatory factors such as cytokines and could represent a functional link between microglia and neuroinflammatory processes. According to transcriptomic databases and in vitro studies, microglia, the main source of cytokines in pathological conditions, express the cannabinoid type 1 receptor (CB1R). Methods: We thus developed a conditional mouse model of CB1R deletion specifically in microglia, which was subjected to an immune challenge (peripheral lipopolysaccharide injection). Results: Our results reveal that microglial CB1R differentially controls sickness behavior in males and females. Conclusion: These findings add to the comprehension of neuroinflammatory processes and might be of great interest for future studies aimed at developing therapeutic strategies for brain disorders with higher prevalence in men.

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.

The endocannabinoidome in neuropsychiatry: Opportunities and potential risks

The endocannabinoid system (ECS) comprises two cognate endocannabinoid receptors referred to as CB1R and CB2R_. ECS dysregulation is apparent in neurodegenerative/neuro-psychiatric disorders including but not limited to schizophrenia, major depressive disorder and potentially bipolar disorder. The aim of this paper is to review mechanisms whereby both receptors may interact with neuro-immune and neuro-oxidative pathways, which play a pathophysiological role in these disorders. CB1R is located in the presynaptic terminals of GABAergic, glutamatergic, cholinergic, noradrenergic and serotonergic neurons where it regulates the retrograde suppression of neurotransmission. CB1R plays a key role in long-term depression, and, to a lesser extent, long-term potentiation, thereby modulating synaptic transmission and mediating learning and memory. Optimal CB1R activity plays an essential neuroprotective role by providing a defense against the development of glutamate-mediated excitotoxicity, which is achieved, at least in part, by impeding AMPA-mediated increase in intracellular calcium overload and oxidative stress. Moreover, CB1R activity enables optimal neuron-glial communication and the function of the neurovascular unit. CB2R receptors are detected in peripheral immune cells and also in central nervous system regions including the striatum, basal ganglia, frontal cortex, hippocampus, amygdala as well as the ventral tegmental area. CB2R upregulation inhibits the presynaptic release of glutamate in several brain regions. CB2R activation also decreases neuroinflammation partly by mediating the transition from a predominantly neurotoxic "M1" microglial phenotype to a more neuroprotective "M2" phenotype. CB1R and CB2R are thus novel drug targets for the treatment of neuro-immune and neuro-oxidative disorders including schizophrenia and affective disorders.

Abstinence from chronic methylphenidate exposure modifies cannabinoid receptor 1 levels in the brain in a dose-dependent manner

INTRODUCTION

Methylphenidate (MP) is a widely used psychostimulant prescribed for Attention Deficit Hyperactivity Disorder, and is also used illicitly by healthy individuals. Chronic exposure to MP has been shown to affect physiology, behavior, and neurochemistry.

METHODS

The present study examined its effect on the endocannabinoid system. Adolescent rats had daily oral access to either water (control), low dose MP (4/10 mg/kg), or high dose MP (30/60 mg/kg). After 13 weeks of exposure, half of the rats in each group were euthanized, however the remaining rats underwent a four-week long abstinence period. Cannabinoid receptor 1 binding (CB1) was measured with in vitro autoradiography using [3H] SR141716A.

RESULTS

Rats who underwent a 4-week abstinence period after exposure to chronic HD MP showed increased binding compared to rats with no abstinence period in several cortical and basal ganglia regions of the brain. In contrast to this, rats who underwent a 4-week abstinence period after exposure to chronic LD MP showed lower binding compared to rats with no abstinence period in mainly the basal ganglia regions and in the hindlimb region of the somatosensory cortex. Following 4 weeks of drug abstinence, rats who were previously given HD MP showed higher [ 3H] SR141716A binding than rats given LD MP in many of the cortical and basal ganglia regions examined. These results highlight biphasic effects of MP treatment on cannabinoid receptor levels. Abstinence from HD MP seemed to increase CB1 receptor levels while abstinence from LD MP seemed to decrease CB1 levels.

CONCLUSION

Given the prolific expression of cannabinoid receptors throughout the brain, many types of behaviors may be affected as a result of MP abstinence. Further research will be needed to help identify these behavioral changes.

Cannabis use and posttraumatic stress disorder comorbidity: Epidemiology, biology and the potential for novel treatment approaches

Cannabis use is increasing among some demographics in the United States and is tightly linked to anxiety, trauma, and stress reactivity at the epidemiological and biological level. Stress-coping motives are highly cited reasons for cannabis use. However, with increased cannabis use comes the increased susceptibility for cannabis use disorder (CUD). Indeed, CUD is highly comorbid with posttraumatic stress disorder (PTSD). Importantly, endogenous cannabinoid signaling systems play a key role in the regulation of stress reactivity and anxiety regulation, and preclinical data suggest deficiencies in this signaling system could contribute to the development of stress-related psychopathology. Furthermore, endocannabinoid deficiency states, either pre-existing or induced by trauma exposure, could provide explanatory insights into the high rates of comorbid cannabis use in patients with PTSD. Here we review clinical and preclinical literature related to the cannabis use-PTSD comorbidity, the role of endocannabinoids in the regulation of stress reactivity, and potential therapeutic implications of recent work in this area.

Cannabinoids, Inner Ear, Hearing, and Tinnitus: A Neuroimmunological Perspective

Cannabis has been used for centuries for recreational and therapeutic purposes. Whereas, the recreative uses are based on the psychotropic effect of some of its compounds, its therapeutic effects range over a wide spectrum of actions, most of which target the brain or the immune system. Several studies have found cannabinoid receptors in the auditory system, both at peripheral and central levels, thus raising the interest in cannabinoid signaling in hearing, and especially in tinnitus, which is affected also by anxiety, memory, and attention circuits where cannabinoid effects are well described. Available studies on animal models of tinnitus suggest that cannabinoids are not likely to be helpful in tinnitus treatment and could even be harmful. However, the pharmacology of cannabinoids is very complex, and most studies focused on neural CB1R-based responses. Cannabinoid effects on the immune system (where CB2Rs predominate) are increasingly recognized as essential in understanding nervous system pathological responses, and data on immune cannabinoid targets have emerged in the auditory system as well. In addition, nonclassical cannabinoid targets (such as TRP channels) appear to play an important role in the auditory system as well. This review will focus on neuroimmunological mechanisms for cannabinoid effects and their possible use as protective and therapeutic agents in the ear and auditory system, especially in tinnitus.

Imbalance of Endocannabinoid/Lysophosphatidylinositol Receptors Marks the Severity of Alzheimer's Disease in a Preclinical Model: A Therapeutic Opportunity

Alzheimer's disease (AD) is the most common form of neurodegeneration and dementia. The endocannabinoid (ECB) system has been proposed as a novel therapeutic target to treat AD. The present study explores the expression of the ECB system, the ECB-related receptor GPR55, and cognitive functions (novel object recognition; NOR) in the 5xFAD (FAD: family Alzheimer's disease) transgenic mouse model of AD. Experiments were performed on heterozygous (HTZ) and homozygous (HZ) 11 month old mice. Protein expression of ECB system components, neuroinflammation markers, and β-amyloid (Aβ) plaques were analyzed in the hippocampus. According to the NOR test, anxiety-like behavior and memory were altered in both HTZ and HZ 5xFAD mice. Furthermore, both animal groups displayed a reduction of cannabinoid (CB1) receptor expression in the hippocampus, which is related to memory dysfunction. This finding was associated with indirect markers of enhanced ECB production, resulting from the combination of impaired monoacylglycerol lipase (MAGL) degradation and increased diacylglycerol lipase (DAGL) levels, an effect observed in the HZ group. Regarding neuroinflammation, we observed increased levels of CB2 receptors in the HZ group that positively correlate with Aβ's accumulation. Moreover, HZ 5xFAD mice also exhibited increased expression of the GPR55 receptor. These results highlight the importance of the ECB signaling for the AD pathogenesis development beyond Aβ deposition.

The "Entourage Effect": Terpenes Coupled with Cannabinoids for the Treatment of Mood Disorders and Anxiety Disorders

Mood disorders are the most prevalent mental conditions encountered in psychiatric practice. Numerous patients suffering from mood disorders present with treatment-resistant forms of depression, co-morbid anxiety, other psychiatric disorders and bipolar disorders. Standardized essential oils (such as that of Lavender officinalis) have been shown to exert clinical efficacy in treating anxiety disorders. As endocannabinoids are suggested to play an important role in major depression, generalized anxiety and bipolar disorders, Cannabis sativa was suggested for their treatment. The endocannabinoid system is widely distributed throughout the body including the brain, modulating many functions. It is involved in mood and related disorders, and its activity may be modified by exogenous cannabinoids. CB1 and CB2 receptors primarily serve as the binding sites for endocannabinoids as well as for phytocannabinoids, produced by cannabis inflorescences. However, ‘cannabis’ is not a single compound product but is known for its complicated molecular profile, producing a plethora of phytocannabinoids alongside a vast array of terpenes. Thus, the “entourage effect” is the suggested positive contribution derived from the addition of terpenes to cannabinoids. Here, we review the literature on the effects of cannabinoids and discuss the possibility of enhancing cannabinoid activity on psychiatric symptoms by the addition of terpenes and terpenoids. Possible underlying mechanisms for the anti-depressant and anxiolytic effects are reviewed. These natural products may be an important potential source for new medications for the treatment of mood and anxiety disorders.

2-Arachidonoylglycerol Modulation of Anxiety and Stress Adaptation: From Grass Roots to Novel Therapeutics

Over the past decade there has been a surge of interest in the development of endocannabinoid-based therapeutic approaches for the treatment of diverse neuropsychiatric conditions. Although initial preclinical and clinical development efforts focused on pharmacological inhibition of fatty acid amide hydrolase to elevate levels of the endocannabinoid anandamide, more recent efforts have focused on inhibition of monoacylglycerol lipase (MAGL) to enhance signaling of the most abundant and efficacious endocannabinoid ligand, 2-arachidonoylglycerol (2-AG). We review the biochemistry and physiology of 2-AG signaling and preclinical evidence supporting a role for this system in the regulation of anxiety-related outcomes and stress adaptation. We review preclinical evidence supporting MAGL inhibition for the treatment of affective, trauma-related, and stress-related disorders; describe the current state of MAGL inhibitor drug development; and discuss biological factors that could affect MAGL inhibitor efficacy. Issues related to the clinical advancement of MAGL inhibitors are also discussed. We are cautiously optimistic, as the field of MAGL inhibitor development transitions from preclinical to clinical and theoretical to practical, that pharmacological 2-AG augmentation could represent a mechanistically novel therapeutic approach for the treatment of affective and stress-related neuropsychiatric disorders.

Stress-induced blood brain barrier disruption: Molecular mechanisms and signaling pathways

Stress is a nonspecific response to a threat or noxious stimuli with resultant damaging consequences. Stress is believed to be an underlying process that can trigger central nervous system disorders such as depression, anxiety, and post-traumatic stress disorder. Though the pathophysiological basis is not completely understood, data have consistently shown a pivotal role of inflammatory mediators and hypothalamo-pituitary-adrenal (HPA) axis activation in stress induced disorders. Indeed emerging experimental evidences indicate a concurrent activation of inflammatory signaling pathways and not only the HPA axis, but also, peripheral and central renin-angiotensin system (RAS). Furthermore, recent experimental data indicate that the HPA and RAS are coupled to the signaling of a range of central neuro-transmitter, -mediator and -peptide molecules that are also regulated, at least in part, by inflammatory signaling cascades and vice versa. More recently, experimental evidences suggest a critical role of stress in disruption of the blood brain barrier (BBB), a neurovascular unit that regulates the movement of substances and blood-borne immune cells into the brain parenchyma, and prevents peripheral injury to the brain substance. However, the mechanisms underlying stress-induced BBB disruption are not exactly known. In this review, we summarize studies conducted on the effects of stress on the BBB and integrate recent data that suggest possible molecular mechanisms and signaling pathways underlying stress-induced BBB disruption. Key molecular targets and pharmacological candidates for treatment of stress and related illnesses are also summarized.

Chronic Psychosocial Stress Causes Increased Anxiety-Like Behavior and Alters Endocannabinoid Levels in the Brain of C57Bl/6J Mice

Introduction: Chronic stress causes a variety of physiological and behavioral alterations, including social impairments, altered endocrine function, and an increased risk for psychiatric disorders. Thereby, social stress is one of the most effective stressful stimuli among mammals and considered to be one of the major risk factors for the onset and progression of neuropsychiatric diseases. For analyzing the effects of social stress in mice, the resident/intruder paradigm of social defeat is a widely used model. Although the chronic social defeat stress model has been extensively studied, little is known about the effects of repeated or chronic social defeat stress on the endocannabinoid system (ECS). The present study aimed to understand the effects of chronic social stress on anxiety behavior and the levels of endocannabinoids (ECs) and two N-acylethanolamines (NAEs) in different brain regions of mice. Materials and Methods: Two-month-old, male C57Bl/6J mice were exposed to chronic psychosocial stress for 3 weeks. The effects of stress on anxiety behavior were measured using the light-dark box and hole board test. The EC levels of 2-arachidonoyl glycerol (2-AG) and anandamide (N-arachidonoylethanolamine [AEA]), as well as the levels of two NAEs (oleoylethanolamide [OEA] and palmitoylethanolamide), were analyzed by liquid chromatography-tandem mass spectrometry in the hippocampus, cerebellum, and cortex. Results: In comparison with control mice (n=12), mice exposed to social defeat stress (n=11) showed increased anxiety behaviors in the light-dark box and hole board test and gained significantly more weight during the experimental period. Additionally, chronic social stress induced differential alterations in the brain levels of 2-AG and AEA. More precisely, 2-AG levels were higher in the cortex and cerebellum, whereas reduced AEA levels were found in the hippocampus. Furthermore, we observed lower OEA levels in the hippocampus. Conclusion: The current study confirms that the ECS plays an essential role in stress responses, whereby its modulation seems to be brain region dependent.

Medicinal cannabis for psychiatric disorders: a clinically-focused systematic review

BACKGROUND

Medicinal cannabis has received increased research attention over recent years due to loosening global regulatory changes. Medicinal cannabis has been reported to have potential efficacy in reducing pain, muscle spasticity, chemotherapy-induced nausea and vomiting, and intractable childhood epilepsy. Yet its potential application in the field of psychiatry is lesser known.

METHODS

The first clinically-focused systematic review on the emerging medical application of cannabis across all major psychiatric disorders was conducted. Current evidence regarding whole plant formulations and plant-derived cannabinoid isolates in mood, anxiety, sleep, psychotic disorders and attention deficit/hyperactivity disorder (ADHD) is discussed; while also detailing clinical prescription considerations (including pharmacogenomics), occupational and public health elements, and future research recommendations. The systematic review of the literature was conducted during 2019, assessing the data from all case studies and clinical trials involving medicinal cannabis or plant-derived isolates for all major psychiatric disorders (neurological conditions and pain were omitted).

RESULTS

The present evidence in the emerging field of cannabinoid therapeutics in psychiatry is nascent, and thereby it is currently premature to recommend cannabinoid-based interventions. Isolated positive studies have, however, revealed tentative support for cannabinoids (namely cannabidiol; CBD) for reducing social anxiety; with mixed (mainly positive) evidence for adjunctive use in schizophrenia. Case studies suggest that medicinal cannabis may be beneficial for improving sleep and post-traumatic stress disorder, however evidence is currently weak. Preliminary research findings indicate no benefit for depression from high delta-9 tetrahydrocannabinol (THC) therapeutics, or for CBD in mania. One isolated study indicates some potential efficacy for an oral cannabinoid/terpene combination in ADHD. Clinical prescriptive consideration involves caution in the use of high-THC formulations (avoidance in youth, and in people with anxiety or psychotic disorders), gradual titration, regular assessment, and caution in cardiovascular and respiratory disorders, pregnancy and breast-feeding.

CONCLUSIONS

There is currently encouraging, albeit embryonic, evidence for medicinal cannabis in the treatment of a range of psychiatric disorders. Supportive findings are emerging for some key isolates, however, clinicians need to be mindful of a range of prescriptive and occupational safety considerations, especially if initiating higher dose THC formulas.

Endocannabinoid Signaling Collapse Mediates Stress-Induced Amygdalo-Cortical Strengthening

Functional coupling between the amygdala and the dorsomedial prefrontal cortex (dmPFC) has been implicated in the generation of negative affective states; however, the mechanisms by which stress increases amygdala-dmPFC synaptic strength and generates anxiety-like behaviors are not well understood. Here, we show that the mouse basolateral amygdala (BLA)-prelimbic prefrontal cortex (plPFC) circuit is engaged by stress and activation of this pathway in anxiogenic. Furthermore, we demonstrate that acute stress exposure leads to a lasting increase in synaptic strength within a reciprocal BLA-plPFC-BLA subcircuit. Importantly, we identify 2-arachidonoylglycerol (2-AG)-mediated endocannabinoid signaling as a key mechanism limiting glutamate release at BLA-plPFC synapses and the functional collapse of multimodal 2-AG signaling as a molecular mechanism leading to persistent circuit-specific synaptic strengthening and anxiety-like behaviors after stress exposure. These data suggest that circuit-specific impairment in 2-AG signaling could facilitate functional coupling between the BLA and plPFC and the translation of environmental stress to affective pathology.

Pharmacotherapy of anxiety disorders in the 21st century: A call for novel approaches

While limited advances have occurred in the past 30 years in the pharmacological management of anxiety and stress-related disorders, novel molecular pathways both within and without the monoamine systems are currently under investigation and offer promising new avenues for more effective future treatments. Enhancing psychotherapy approaches with pharmacological compounds offers the potential to not only transform the standard of care of these conditions, but more broadly would introduce a paradigm shift in the way medications and their role in psychiatric care are conceptualised. Although further human trials and more translational research are sorely needed, continuing to pursue innovative mechanisms and treatments is hoped to yield substantial results in the coming decades and a departure from the reliance on chemical agents of the 20th century.

Role of the endocannabinoid system in the dorsal hippocampus in the cardiovascular changes and delayed anxiety-like effect induced by acute restraint stress in rats

BACKGROUND

The dorsal hippocampus has a central role in modulating cardiovascular responses and behavioral adaptation to stress. The dorsal hippocampus also plays a key role in stress-associated mental disorders. The endocannabinoid system is widely expressed in the dorsal hippocampus and modulates defensive behaviors under stressful conditions. The endocannabinoid anandamide activates cannabinoid type 1 receptors and is metabolized by the fatty acid amide hydrolase enzyme.

AIMS

We sought to verify whether cannabinoid type 1 receptors modulate stress-induced cardiovascular changes, and if pharmacological fatty acid amide hydrolase inhibition in the dorsal hippocampus would prevent the cardiovascular responses and the delayed anxiogenic-like behavior evoked by restraint stress in rats via cannabinoid type 1 receptors.

METHODS

Independent groups received intra-dorsal-hippocampal injections of N-(piperidin-1yl)-5-(4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-hpyrazole-3-carboxamide (AM251; cannabinoid type 1 receptor antagonist/inverse agonist, 10-300 pmol) and/or cyclohexyl carbamic acid 3'-carbamoyl-biphenyl-3-yl ester (URB597; fatty acid amide hydrolase inhibitor, 10 pmol) before the restraint stress session. Cardiovascular response during restraint stress or later behavioral parameters were evaluated.

RESULTS

Acute restraint stress altered the cardiovascular response, characterized by increased heart rate and mean arterial pressure, as well as decreased tail cutaneous temperature. It also induced a delayed anxiogenic-like effect, evidenced by reduced open arm exploration in the elevated plus maze 24 h after stress. AM251 exacerbated the stress-induced cardiovascular responses after injection into the dorsal hippocampus. In contrast, local injection of URB597 prevented the cardiovascular response and the delayed (24 h) behavioral consequences of restraint stress, effects attenuated by pretreatment with AM251.

CONCLUSION

Our data corroborate previous results indicating that the hippocampal endocannabinoid system modulates the outcome of stress exposure and suggest that this could involve modulation of the cardiovascular response during stress exposure.

A review on inflammatory cytokine-induced alterations of the brain as potential neural biomarkers in post-traumatic stress disorder

The heterogeneity of post-traumatic stress disorder (PTSD) symptoms indicates that multiple neurobiological mechanisms underlie the pathophysiology of the condition. However, no generally accepted PTSD biomarkers in clinical practice currently exist. The sequential responses to recurrent and chronic stress by the hypothalamic-pituitary-adrenal (HPA) axis and the autonomic nervous system (ANS) system are considered to play a significant role in the onset and progression of PTSD. Decreased activity of the HPA axis and parasympathetic nervous system, along with increased activity of the sympathetic nervous system, have been observed in PTSD, which may lead to increased levels of proinflammatory cytokines. Such heightened activity of the immune system may cause alterations in the structure and function of brain regions-for example, the amygdala, hippocampus, medial prefrontal cortex, anterior cingulate cortex, and insula-through changes in levels of serotonin and kynurenine pathway metabolites, and direct neurotoxic effects of cytokines. Although chronic inflammation-induced alterations in brain regions critical in controlling emotional behavior and fear regulation may represent a strong candidate biomarker of PTSD, future studies are necessary to further elucidate inflammation-associated neural biomarkers of PTSD. Continued research on therapeutic methods that involve the normalization of the HPA axis, ANS, and immune system is expected to contribute to the development of novel ways to treat PTSD.

Cannabis and the Anxiety of Fragmentation-A Systems Approach for Finding an Anxiolytic Cannabis Chemotype

Cannabis sativa is a medicinal herb with a diverse range of chemotypes that can exert both anxiolytic and anxiogenic effects on humans. Medical cannabis patients receiving organically grown cannabis from a single source were surveyed about the effectiveness of cannabis for treating anxiety. Patients rated cannabis as highly effective overall for treating anxiety with an average score of 8.03 on a Likert scale of 0 to 10 (0 = not effective, 10 = extremely effective). Patients also identified which strains they found the most or least effective for relieving their symptoms of anxiety. To find correlations between anxiolytic activity and chemotype, the top four strains voted most and least effective were analyzed by HPLC-MS/MS to quantify cannabinoids and GC-MS to quantify terpenes. Tetrahydrocannabinol (THC) and trans-nerolidol have statistically significant correlations with increased anxiolytic activity. Guiaol, eucalyptol, γ-terpinene, α-phellandrene, 3-carene, and sabinene hydrate all have significant correlations with decreased anxiolytic activity. Further studies are needed to better elucidate the entourage effects that contribute to the anxiolytic properties of cannabis varieties.

Repeated social defeat-induced neuroinflammation, anxiety-like behavior and resistance to fear extinction were attenuated by the cannabinoid receptor agonist WIN55,212-2

Psychosocial stress contributes to the development of psychiatric disorders. Repeated social defeat (RSD) is a murine stressor that causes a release of inflammatory monocytes into circulation. Moreover, RSD-induced anxiety-like behavior is dependent on the recruitment of these monocytes to the brain. Activation of the endocannabinoid (ECB) system may modulate both neuroendocrine and inflammatory responses mediated by stress. Therefore, we hypothesized that a cannabinoid receptor agonist would attenuate RSD-induced inflammation, anxiety, and stress sensitization. To test this hypothesis, mice received an injection of the synthetic cannabinoid_1/2 receptor agonist, WIN55,212-2 (WIN; 1 mg/kg, intraperitoneally) daily for six consecutive days, 30 min before each exposure to RSD. Anxiety-like behavior, immune activation, neuroinflammation, and microglial reactivity were determined 14 h after RSD. RSD-induced anxiety-like behavior in the open field and in the EPM was reversed by WIN55,212-2. Moreover, WIN55,212-2 reduced the accumulation of inflammatory monocytes in circulation and brain after RSD and attenuated RSD-induced interleukin-1β (IL-1β) messenger RNA (mRNA) expression in microglia/macrophages. Increased ex vivo reactivity of microglia/monocytes to lipopolysaccharides (LPS) after RSD was also attenuated by WIN55,212-2. Next, fear expression, extinction, and recall were evaluated 24 and 48 h, respectively, after contextual fear conditioning, which took place 7 days after RSD. Here, RSD caused prolonged fear expression and impaired fear extinction recall, which was associated with increased IL-1β mRNA in the brain. Moreover, these stress-induced effects were reversed by WIN55,212-2. In conclusion, activation of cannabinoid receptors limited the immune and neuroinflammatory responses to RSD and reversed the short-term and long-term behavioral deficits associated with RSD.

The Endocannabinoid Reuptake Inhibitor WOBE437 Is Orally Bioavailable and Exerts Indirect Polypharmacological Effects via Different Endocannabinoid Receptors

Different anandamide (AEA) transport inhibitors show antinociceptive and antiinflammatory effects in vivo, but due to their concomitant inhibition of fatty acid amide hydrolase (FAAH) and overall poor bioavailability, they cannot be used unequivocally to study the particular role of endocannabinoid (EC) transport in pathophysiological conditions in vivo. Here, the potent and selective endocannabinoid reuptake inhibitor WOBE437, which inhibits AEA and 2-arachidonoylglycerol (2-AG) transport, was tested for its oral bioavailability to the brain. WOBE437 is assumed to locally increase EC levels in tissues in which facilitated EC reuptake intermediates subsequent hydrolysis. Given the marked polypharmacology of ECs, we hypothesized to see differential effects on distinct EC receptors in animal models of acute and chronic pain/inflammation. In C57BL6/J male mice, WOBE437 was orally bioavailable with an estimated t_max value of ≤20 min in plasma (C_max ∼ 2000 pmol/mL after 50 mg/kg, p.o.) and brain (C_max ∼ 500 pmol/g after 50 mg/kg, p.o.). WOBE437 was cleared from the brain after approximately 180 min. In addition, in BALB/c male mice, acute oral administration of WOBE437 (50 mg/kg) exhibited similar brain concentrations after 60 min and inhibited analgesia in the hot plate test in a cannabinoid CB1 receptor-dependent manner, without inducing catalepsy or affecting locomotion. WOBE437 significantly elevated AEA in the somatosensory cortex, while showing dose-dependent biphasic effects on 2-AG levels in plasma but no significant changes in N-acylethanolamines other than AEA in any of the tissues. In order to explore the presumed polypharmacology mediated via elevated EC levels, we tested this EC reuptake inhibitor in complete Freud's adjuvant induced monoarthritis in BALB/c mice as a model of chronic inflammation. Repetitive doses of WOBE437 (10 mg/kg, i.p.) attenuated allodynia and edema via cannabinoid CB2, CB1, and PPARγ receptors. The allodynia inhibition of WOBE437 treatment for 3 days was fully reversed by antagonists of any of the receptors. In the single dose treatment the CB2 and TRPV1 antagonists significantly blocked the effect of WOBE437. Overall, our results show the broad utility of WOBE437 for animal experimentation for both p.o. and i.p. administrations. Furthermore, the data indicate the possible involvement of EC reuptake/transport in pathophysiological processes related to pain and inflammation.