Enhancement of endocannabinoid signaling and the pharmacotherapy of depression

The endocannabinoid system is involved in the anxiety-like behavior induced by dual-frequency 2.65/0.8 GHz electromagnetic radiation in mice

As wireless communication devices gain popularity, concerns about the potential risks of environmental exposure to complex frequency electromagnetic radiation (EMR) on mental health have become a public health issue. Historically, EMR research has predominantly focused on single- frequency electromagnetic waves, neglecting the study of multi-frequency electromagnetic waves, which more accurately represent everyday life. To address these concerns, our study compared the emotional effects of single-frequency and dual-frequency EMR while exploring potential molecular mechanisms and intervention targets. Our results revealed that single-frequency EMR at 2.65 or 0.8 GHz did not induce anxiety-like behavior in mice. However, exposure to dual-frequency EMR at 2.65/0.8 GHz significantly led to anxiety-like behavior in mice. Further analysis of mouse sera revealed substantial increases in corticosterone and corticotrophin releasing hormone levels following exposure to 2.65/0.8 GHz EMR. Transcriptome sequencing indicated a significant decrease in the expression of Cnr1, encoding cannabinoid receptor 1 Type (CB1R), in the cerebral. This finding was consistently verified through western blot analysis, revealing a substantial reduction in CB1R content. Additionally, a significant decrease in the endocannabinoid 2-arachidonoylglycerol was observed in the cerebral cortex. Remarkably, administering the cannabinoid receptor agonist Win55-212-2 significantly alleviated the anxiety-like behavior, and the cannabinoid receptor antagonist AM251 effectively counteracted the anti-anxiety effects of Win55-212-2. In summary, our research confirmed that dual-frequency EMR is more likely to induce anxiety-like behavior in mice than single-frequency EMR, with implications for the hypothalamic-pituitary-adrenal axis and the endocannabinoid system. Furthermore, our findings suggest that Win55-212-2 may represent a novel avenue for researching and developing anti-EMR drugs.

A Novel Anti-Inflammatory Formulation Comprising Celecoxib and Cannabidiol Exerts Antidepressant and Anxiolytic Effects

Background: Ample research shows that anti-inflammatory drugs, particularly celecoxib, exert antidepressant effects, especially in patients with microglia activation. However, substantial cardiovascular adverse effects limit celecoxib's usefulness. Given that cannabidiol (CBD) exerts anti-inflammatory, microglia-suppressive, and antidepressant effects, we hypothesized that it may potentiate the therapeutic effects of celecoxib. Methods: The effects of celecoxib, CBD, and their combination were examined in murine models of antidepressant- and anxiolytic-like behavioral responsiveness, including the forced swim test (FST), elevated plus maze (EPM), lipopolysaccharide (LPS)-induced neuroinflammation, and chronic social defeat stress (CSDS), as well as in microglia cell cultures. Results: Acute administration of a combination of celecoxib plus CBD, at doses that had no effects by themselves (10 and 5 mg/kg, respectively), produced significant antidepressant- and anxiolytic-like effects in the FST and EPM, in male and female mice. In the LPS model, combinations of celecoxib (10 or 20 mg/kg) plus CBD (30 mg/kg) reversed the anxiety-like behavior in the open-field test (OFT) and anhedonia in the sucrose preference test (SPT), with minimal effects of celecoxib or CBD by themselves. In the CSDS paradigm, a combination of celecoxib plus CBD (each at 30 mg/kg) reversed the deficits in the OFT, EPM, social exploration, and SPT, whereas celecoxib or CBD by themselves had partial effects. In BV2 microglia cultures stimulated with LPS or α-synuclein, CBD markedly potentiated the suppressive effects of celecoxib over TNFα (tumor necrosis factor-α) and IL (interleukin)-1β secretion. Conclusions: Combinations of celecoxib plus CBD produce efficacious antidepressant- and anxiolytic-like effects, which may depend on their synergistic microglia-suppressive effects.

The Main Therapeutic Applications of Cannabidiol (CBD) and Its Potential Effects on Aging with Respect to Alzheimer's Disease

The use of cannabinoids (substances contained specifically in hemp plants) for therapeutic purposes has received increased attention in recent years. Presently, attention is paid to two main cannabinoids: delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD). With respect to the psychotropic effects and dependence potential of THC (though it is very mild), its use is associated with certain restrictions, and thus the therapeutic properties of CBD are frequently emphasized because there are no limitations associated with the risk of dependence. Therefore, this review covers the main pharmacodynamic and pharmacokinetic features of CBD (including characteristics of endocannabinoidome) with respect to its possible beneficial effects on selected diseases in clinical practice. A substantial part of the text deals with the main effects of CBD on aging, including Alzheimer's disease and related underlying mechanisms.

The cannabinoid system and microglia in health and disease

Recent years have yielded significant advances in our understanding of microglia, the immune cells of the central nervous system (CNS). Microglia are key players in CNS development, immune surveillance, and the maintenance of proper neuronal function throughout life. In the healthy brain, homeostatic microglia have a unique molecular signature. In neurological diseases, microglia become activated and adopt distinct transcriptomic signatures, including disease-associated microglia (DAM) implicated in neurodegenerative disorders. Homeostatic microglia synthesise the endogenous cannabinoids 2-arachidonoylglycerol and anandamide and express the cannabinoid receptors CB1 and CB2 at constitutively low levels. Upon activation, microglia significantly increase their synthesis of endocannabinoids and upregulate their expression of CB2 receptors, which promote a protective microglial phenotype by enhancing their production of neuroprotective factors and reducing their production of pro-inflammatory factors. Here, we summarise the effects of the microglial cannabinoid system in the CNS demyelinating disease multiple sclerosis, the neurodegenerative diseases Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis, chronic inflammatory and neuropathic pain, and psychiatric disorders including depression, anxiety and schizophrenia. We discuss the therapeutic potential of cannabinoids in regulating microglial activity and highlight the need to further investigate their specific microglia-dependent immunomodulatory effects.

Serotonin 2A receptors and cannabinoids

Accumulating evidence has proven that both exogenous cannabinoids as well as imbalances in the endocannabinoid system are involved in the onset and development of mental disorders such as anxiety, depression, or schizophrenia. Extensive recent research in this topic has mainly focused on the molecular mechanisms by which cannabinoid agonists may contribute to the pathophysiology of these disorders. Initially, serotonin neurotransmitter garnered most attention due to its relationship to mood disorders and mental diseases, with little attention to specific receptors. To date, the focus has redirected toward the understanding of different serotonin receptors, through a demonstration of its versatile pharmacology and synergy with different modulators. Serotonin 2A receptors are a good example of this phenomenon, and the complex signaling that they trigger appears of high relevance in the context of mental disorders, especially in schizophrenia. This chapter will analyze most relevant attributes of serotonin 2A receptors and the endocannabinoid system, and will highlight the evidence toward the functional bidirectional interaction between these elements in the brain as well as the impact of the endocannabinoid system dysregulation on serotonin 2A receptors functionality.

Do Adolescent Exposure to Cannabinoids and Early Adverse Experience Interact to Increase the Risk of Psychiatric Disorders: Evidence from Rodent Models

There have been growing concerns about the protracted effects of cannabis use in adolescents on emotion and cognition outcomes, motivated by evidence of growing cannabis use in adolescents, evidence linking cannabis use to various psychiatric disorders, and the increasingly perceived notion that cannabis is harmless. At the same time, studies suggest that cannabinoids may have therapeutic potential against the impacts of stress on the brain and behavior, and that young people sometimes use cannabinoids to alleviate feelings of depression and anxiety (i.e., “self-medication”). Exposure to early adverse life events may predispose individuals to developing psychopathology in adulthood, leading researchers to study the causality between early life factors and cognitive and emotional outcomes in rodent models and to probe the underlying mechanisms. In this review, we aim to better understand the long-term effects of cannabinoids administered in sensitive developmental periods (mainly adolescence) in rodent models of early life stress. We suggest that the effects of cannabinoids on emotional and cognitive function may vary between different sensitive developmental periods. This could potentially affect decisions regarding the use of cannabinoids in clinical settings during the early stages of development and could raise questions regarding educating the public as to potential risks associated with cannabis use.

Exo- and Endo-cannabinoids in Depressive and Suicidal Behaviors

Cannabis (marijuana) has been known to humans for thousands of years but its neurophysiological effects were sparsely understood until recently. Preclinical and clinical studies in the past two decades have indisputably supported the clinical proposition that the endocannabinoid system plays an important role in the etiopathogeneses of many neuropsychiatric disorders, including mood and addictive disorders. In this review, we discuss the existing knowledge of exo- and endo-cannabinoids, and role of the endocannabinoid system in depressive and suicidal behavior. A dysfunction in this system, located in brain regions such as prefrontal cortex and limbic structures is implicated in mood regulation, impulsivity and decision-making, may increase the risk of negative mood and cognition as well as suicidality. The literature discussed here also suggests that the endocannabinoid system may be a viable target for treatments of these neuropsychiatric conditions.

Inhibition of fatty acid amide hydrolase prevents pathology in neurovisceral acid sphingomyelinase deficiency by rescuing defective endocannabinoid signaling

Acid sphingomyelinase deficiency (ASMD) leads to cellular accumulation of sphingomyelin (SM), neurodegeneration, and early death. Here, we describe the downregulation of the endocannabinoid (eCB) system in neurons of ASM knockout (ASM‐KO) mice and a ASMD patient. High SM reduced expression of the eCB receptor CB₁ in neuronal processes and induced its accumulation in lysosomes. Activation of CB₁ receptor signaling, through inhibition of the eCB‐degrading enzyme fatty acid amide hydrolase (FAAH), reduced SM levels in ASM‐KO neurons. Oral treatment of ASM‐KO mice with a FAAH inhibitor prevented SM buildup; alleviated inflammation, neurodegeneration, and behavioral alterations; and extended lifespan. This treatment showed benefits even after a single administration at advanced disease stages. We also found CB₁ receptor downregulation in neurons of a mouse model and a patient of another sphingolipid storage disorder, Niemann–Pick disease type C (NPC). We showed the efficacy of FAAH inhibition to reduce SM and cholesterol levels in NPC patient‐derived cells and in the brain of a NPC mouse model. Our findings reveal a pathophysiological crosstalk between neuronal SM and the eCB system and offer a new treatment for ASMD and other sphingolipidoses.

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.

Physiology of the Endocannabinoid System During Development

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

Effects of cannabidiol in males and females in two different rat models of depression

The current study explores the therapeutic potential of Cannabidiol (CBD), a compound in the Cannabis plant, using both sexes of 2 "depressive-like" genetic models, Wistar Kyoto (WKY) and Flinders Sensitive Line (FSL) rats. Rats ingested CBD (30 mg/kg) orally. In the saccharin preference test, following a previous report of a pro-hedonic effect of CBD in male WKY, we now found similar results in female WKY. CBD also decreased immobility in the forced swim test in males (both strains) and in female WKY. These findings suggest a role for CBD in treating mental disorders with prominent symptoms of helplessness and anhedonia.

Metabolomics of postprandial plasma alterations: a comprehensive Japanese study

While endogenous metabolites in plasma can be used as clinical biomarkers, intra-day variations should be carefully considered. The postprandial effect is a large contributing factor and is dependent on regional features (e.g. meals, ethnicity). Thus, for clinical application, regional-specific postprandial baseline data are required. In this study, 10 healthy Japanese volunteers of different ages and genders ate the same meal, and blood samples were taken 30 min before and 1 h after the meal challenge. Plasma metabolomics was conducted and metabolites that significantly changed with the meal challenge were extracted. Principal component analysis of the data from 1101 metabolites showed a postprandial shift with a common direction despite marked individual variation. Pathway enrichment analysis demonstrated known postprandial effects, including the energy utilization shift from lipolysis to glycolysis and the elevation of bile acids for lipid absorption. Other postprandial metabolic changes were observed, including decreases in orexigenic signals and increases of food-derived components. The postprandial alteration accumulated in this study will be used for the understanding of Japanese clinical metabolomics for health promotion in Japan.

Endocannabinoid-Mediated Plasticity in Nucleus Accumbens Controls Vulnerability to Anxiety after Social Defeat Stress

Chronic social defeat stress (CSDS) is a clinically relevant model of mood disorders. The relationship between the CSDS model and a physiologically pertinent paradigm of synaptic plasticity is not known. Here, we found that cluster analysis of the emotional behavior states of mice exposed to CSDS allowed their segregation into anxious and non-anxious groups. Endocannabinoid-mediated spike-timing dependent plasticity (STDP) in the nucleus accumbens was attenuated in non-anxious mice and abolished in anxious mice. Anxiety-like behavior in stressed animals was specifically correlated with their ability to produce STDP. Pharmacological enhancement of 2-arachidonoyl glycerol (2-AG) signaling in the nucleus accumbens normalized the anxious phenotype and STDP in anxious mice. These data reveal that endocannabinoid modulation of synaptic efficacy in response to a naturalistic activity pattern is both a molecular correlate of behavioral adaptability and a crucial factor in the adaptive response to chronic stress.

Cannabis for posttraumatic stress disorder: A neurobiological approach to treatment

The endocannabinoid system is intricately involved in regulation of the neurobiological processes, which underlie the symptomatology of posttraumatic stress disorder (PTSD). This article discusses the neurobiological underpinnings of PTSD and the use of cannabis for treating PTSD in the New Mexico Medical Cannabis Program.

Developmental regulation of fear learning and anxiety behavior by endocannabinoids

The developing brain undergoes substantial maturation into adulthood and the development of specific neural structures occurs on differing timelines. Transient imbalances between developmental trajectories of corticolimbic structures, which are known to contribute to regulation over fear learning and anxiety, can leave an individual susceptible to mental illness, particularly anxiety disorders. There is a substantial body of literature indicating that the endocannabinoid (eCB) system critically regulates stress responsivity and emotional behavior throughout the life span, making this system a novel therapeutic target for stress- and anxiety-related disorders. During early life and adolescence, corticolimbic eCB signaling changes dynamically and coincides with different sensitive periods of fear learning, suggesting that eCB signaling underlies age-specific fear learning responses. Moreover, perturbations to these normative fluctuations in corticolimbic eCB signaling, such as stress or cannabinoid exposure, could serve as a neural substrate contributing to alterations to the normative developmental trajectory of neural structures governing emotional behavior and fear learning. In this review, we first introduce the components of the eCB system and discuss clinical and rodent models showing eCB regulation of fear learning and anxiety in adulthood. Next, we highlight distinct fear learning and regulation profiles throughout development and discuss the ontogeny of the eCB system in the central nervous system, and models of pharmacological augmentation of eCB signaling during development in the context of fear learning and anxiety.

Facilitatory effect of AM281 on recognition memory in rats

BACKGROUND

Our approach was to determine the influence of a single systemic administration of AM281, synthetic cannabinoid structurally similar to SR141716A, on recognition memory in rats.

METHODS

To assess the influence of AM281 on acquisition of information the compound was given intraperitoneally once, at the doses of 0.1, 0.5, 1.0 or 2.0mg/kg, 15min before learning trial (T1) and in order to evaluate its influence on consolidation process AM281 was given at indicated doses, immediately after T1 trial in an object recognition test. Since cannabinoids may alter motor function and affect anxiety, the influence of AM281 on psychomotor activity and anxiety was evaluated in an open-field and elevated plus maze test, respectively.

RESULTS

Administration of AM281 at the doses: 0.1, 0.5 and 1.0mg/kg significantly improved acquisition of information, while 0.1 and 0.5mg/kg of AM281 significantly facilitated consolidation process. Not only did AM281 not affect locomotor and exploratory activity, but also anxiety.

CONCLUSION

This is the first evidence that AM281 exerts facilitatory effect on recognition memory in rats. This effect seems to be memory specific because no alterations in animals' psychomotor activity and anxiety were observed.

Monoacylglycerol lipase inhibition blocks chronic stress-induced depressive-like behaviors via activation of mTOR signaling

The endocannabinoid (eCB) system regulates mood, emotion, and stress coping, and dysregulation of the eCB system is critically involved in pathophysiology of depression. The eCB ligand 2-arachidonoylglycerol (2-AG) is inactivated by monoacylglycerol lipase (MAGL). Using chronic unpredictable mild stress (CUS) as a mouse model of depression, we examined how 2-AG signaling in the hippocampus was altered in depressive-like states and how this alteration contributed to depressive-like behavior. We report that CUS led to impairment of depolarization-induced suppression of inhibition (DSI) in mouse hippocampal CA1 pyramidal neurons, and this deficiency in 2-AG-mediated retrograde synaptic depression was rescued by MAGL inhibitor JZL184. CUS induced depressive-like behaviors and decreased mammalian target of rapamycin (mTOR) activation in the hippocampus, and these biochemical and behavioral abnormalities were ameliorated by chronic JZL184 treatments. The effects of JZL184 were mediated by cannabinoid CB1 receptors. Genetic deletion of mTOR with adeno-associated viral (AAV) vector carrying the Cre recombinase in the hippocampus of mTORf/f mice recapitulated depressive-like behaviors induced by CUS and abrogated the antidepressant-like effects of chronic JZL184 treatments. Our results suggest that CUS decreases eCB-mTOR signaling in the hippocampus, leading to depressive-like behaviors, whereas MAGL inhibitor JZL184 produces antidepressant-like effects through enhancement of eCB-mTOR signaling.

Long-term consequences of perinatal fatty acid amino hydrolase inhibition

BACKGROUND AND PURPOSE

Fatty acid amide hydrolase inhibitors show promise as a treatment for anxiety, depression and pain. Here we investigated whether perinatal exposure to URB597, a fatty acid amide hydrolase inhibitor, alters brain development and affects behaviour in adult mice.

EXPERIMENTAL APPROACH

Mouse dams were treated daily from gestational day 10.5 to 16.5 with 1, 3 or 10 mg kg−1 URB597. MS was used to measure a panel of endocannabinoids and related lipid compounds and brain development was assessed at embryonic day 16.5. Separate cohorts of mouse dams were treated with 10 mg kg−1 URB597, from gestational day 10.5 to postnatal day 7, and the adult offspring were assessed with a battery of behavioural tests.

KEY RESULTS

Perinatal URB597 exposure elevated anandamide and related N-acyl amides. URB597 did not induce signs of toxicity or affect dam weight gain, neurogenesis or axonal development at embryonic day 16.5. It did lead to subtle behavioural deficits in adult offspring, manifested by reduced cocaine-conditioned preference, increased depressive behaviours and impaired working memory. Anxiety levels, motor function and sensory-motor gating were not significantly altered.

CONCLUSIONS AND IMPLICATIONS

Taken together, the present results highlight how exposure to elevated levels of anandamide and related N-acyl amides during brain development can lead to subtle alterations in behaviour in adulthood.

LINKED ARTICLES

This article is part of a themed section on Cannabinoids 2013. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2014.171.issue-6

Metabolic disturbances connecting obesity and depression

Obesity markedly increases the odds of developing depression. Depressed mood not only impairs motivation, quality of life and overall functioning but also increases the risks of obesity complications. Abdominal obesity is a better predictor of depression and anxiety risk than overall adipose mass. A growing amount of research suggests that metabolic abnormalities stemming from central obesity that lead to metabolic disease may also be responsible for the increased incidence of depression in obesity. As reviewed here, a higher mass of dysfunctional adipose tissue is associated with several metabolic disturbances that are either directly or indirectly implicated in the control of emotions and mood. To better comprehend the development of depression in obesity, this review pulls together select findings addressing the link between adiposity, diet and negative emotional states and discusses the evidence that alterations in glucocorticoids, adipose-derived hormones, insulin and inflammatory signaling that are characteristic of central obesity may be involved.

Substrate-selective COX-2 inhibition decreases anxiety via endocannabinoid activation

Augmentation of endogenous cannabinoid (eCB) signaling represents an emerging approach to the treatment of affective disorders. Cyclooxygenase-2 (COX-2) oxygenates arachidonic acid to form prostaglandins, but also inactivates eCBs in vitro. However, the viability of COX-2 as a therapeutic target for in vivo eCB augmentation has not been explored. Using medicinal chemistry and in vivo analytical and behavioral pharmacological approaches, we found that COX-2 is important for the regulation of eCB levels in vivo. We used a pharmacological strategy involving substrate-selective inhibition of COX-2 to augment eCB signaling without affecting related non-eCB lipids or prostaglandin synthesis. Behaviorally, substrate-selective inhibition of COX-2 reduced anxiety-like behaviors in mice via increased eCB signaling. Our data suggest a key role for COX-2 in the regulation of eCB signaling and indicate that substrate-selective pharmacology represents a viable approach for eCB augmentation with broad therapeutic potential.

Selective inhibition of alpha/beta-hydrolase domain 6 attenuates neurodegeneration, alleviates blood brain barrier breakdown, and improves functional recovery in a mouse model of traumatic brain injury

2-arachidonylglycerol (2-AG) is the most abundant endocannabinoid in the central nervous system and is elevated after brain injury. Because of its rapid hydrolysis, however, the compensatory and neuroprotective effect of 2-AG is short-lived. Although inhibition of monoacylglycerol lipase, a principal enzyme for 2-AG degradation, causes a robust increase of brain levels of 2-AG, it also leads to cannabinoid receptor desensitization and behavioral tolerance. Alpha/beta hydrolase domain 6 (ABHD6) is a novel 2-AG hydrolytic enzyme that accounts for a small portion of 2-AG hydrolysis, but its inhibition is believed to elevate the levels of 2-AG within the therapeutic window without causing side effect. Using a mouse model of traumatic brain injury (TBI), we found that post-insult chronic treatment with a selective ABHD6 inhibitor WWL70 improved motor coordination and working memory performance. WWL70 treatment reduced lesion volume in the cortex and neurodegeneration in the dendate gyrus. It also suppressed the expression of inducible nitric oxide synthase and cyclooxygenase-2 and enhanced the expression of arginase-1 in the ipsilateral cortex at 3 and 7 days post-TBI, suggesting microglia/macrophages shifted from M1 to M2 phenotypes after treatment. The blood-brain barrier dysfunction at 3 and 7 days post-TBI was dramatically reduced. Furthermore, the beneficial effects of WWL70 involved up-regulation and activation of cannabinoid type 1 and type 2 receptors and were attributable to the phosphorylation of the extracellular signal regulated kinase and the serine/threonine protein kinase AKT. This study indicates that the fine-tuning of 2-AG signaling by modulating ABHD6 activity can exert anti-inflammatory and neuroprotective effects in TBI.

GPR55, a G-protein coupled receptor for lysophosphatidylinositol, plays a role in motor coordination

The G-protein coupled receptor 55 (GPR55) is activated by lysophosphatidylinositols and some cannabinoids. Recent studies found prominent roles for GPR55 in neuropathic/inflammatory pain, cancer and bone physiology. However, little is known about the role of GPR55 in CNS development and function. To address this question, we performed a detailed characterization of GPR55 knockout mice using molecular, anatomical, electrophysiological, and behavioral assays. Quantitative PCR studies found that GPR55 mRNA was expressed (in order of decreasing abundance) in the striatum, hippocampus, forebrain, cortex, and cerebellum. GPR55 deficiency did not affect the concentrations of endocannabinoids and related lipids or mRNA levels for several components of the endocannabinoid system in the hippocampus. Normal synaptic transmission and short-term as well as long-term synaptic plasticity were found in GPR55 knockout CA1 pyramidal neurons. Deleting GPR55 function did not affect behavioral assays assessing muscle strength, gross motor skills, sensory-motor integration, motor learning, anxiety or depressive behaviors. In addition, GPR55 null mutant mice exhibited normal contextual and auditory-cue conditioned fear learning and memory in a Pavlovian conditioned fear test. In contrast, when presented with tasks requiring more challenging motor responses, GPR55 knockout mice showed impaired movement coordination. Taken together, these results suggest that GPR55 plays a role in motor coordination, but does not strongly regulate CNS development, gross motor movement or several types of learned behavior.

Cannabinoids and monoamine neurotransmission with focus on monoamine oxidase

Progress in understanding the mechanisms of action of cannabinoids was made after discovery of cannabinoid receptors and finding their endogenous ligands. New findings are obtained using both endogenous cannabinoids and plant or synthetic cannabinoids. Activation of cannabinoid receptors on synaptic terminals results in regulation of ion channels, neurotransmitter release and synaptic plasticity. Neuromodulation of synapses by cannabinoids is proving to have a wide range of functional effects, making them potential targets as medical preparations in a variety of illnesses, including some neurodegenerative and mental disorders. Brain monoamines are involved in many of the same processes affected by neuropsychiatric disorders and by different psychotropic drugs, including cannabinoids. Basic information is summarized in the paper about mechanisms of action of cannabinoids on monoaminergic systems, with a view to inhibition of monoamine oxidase.

Dysfunction in fatty acid amide hydrolase is associated with depressive-like behavior in Wistar Kyoto rats

Background

While the etiology of depression is not clearly understood at the present time, this mental disorder is thought be a complex and multifactorial trait with important genetic and environmental contributing factors.

Methodology/Principal Findings

The role of the endocannabinoid (eCB) system in depressive behavior was examined in Wistar Kyoto (WKY) rat strain, a genetic model of depression. Our findings revealed selective abnormalities in the eCB system in the brains of WKY rats compared to Wistar (WIS) rats. Immunoblot analysis indicated significantly higher levels of fatty acid amide hydrolase (FAAH) in frontal cortex and hippocampus of WKY rats with no alteration in the level of N-arachidonyl phosphatidyl ethanolamine specific phospholipase-D (NAPE-PLD). Significantly higher levels of CB1 receptor-mediated G-protein coupling and lower levels of anandamide (AEA) were found in frontal cortex and hippocampus of WKY rats. While the levels of brain derived neurotropic factor (BDNF) were significantly lower in frontal cortex and hippocampus of WKY rats compared to WIS rats, pharmacological inhibition of FAAH elevated BDNF levels in WKY rats. Inhibition of FAAH enzyme also significantly increased sucrose consumption and decreased immobility in the forced swim test in WKY rats.

Conclusions/Significance

These findings suggest a critical role for the eCB system and BDNF in the genetic predisposition to depressive-like behavior in WKY rats and point to the potential therapeutic utility of eCB enhancing agents in depressive disorder.

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

The endocannabinoid system shows functional activity from early stages of brain development: it plays an important role in fundamental developmental processes such as cell proliferation, migration, and differentiation, thus shaping brain organization during pre- and postnatal life. Cannabis sativa preparations are among the illicit drugs most commonly used by young people, including pregnant women. The developing brain can be therefore exposed to cannabis preparations during two critical periods: first, in offspring of cannabis-using mothers through perinatal and/or prenatal exposure; second, in adolescent cannabis users during neural maturation. In the last decade, it has become clear that the endocannabinoid system critically modulates memory processing and emotional responses. Therefore, it is well possible that developmental exposure to cannabinoid compounds induces enduring changes in behaviors and neural processes belonging to the cognitive and emotional domains. We address this issue by focusing on rodent studies, in order to provide a framework for understanding the impact of cannabinoid exposure on the developing brain.

The endocannabinoid system in the regulation of emotions throughout lifespan: a discussion on therapeutic perspectives

Alterations in emotion regulation processes may form the basis of psychopathologies. The endocannabinoid (eCB) system, composed of endogenous ligands, the enzymatic machinery in charge of their metabolism and the specific metabotropic receptors, has emerged as a major neuromodulatory system critically involved in the control of emotional homeostasis and stress responsiveness. Data from animal models indicate that the eCB system plays a key role in brain development, and is probably involved in the control of emotional states from early developmental stages. The present review summarizes the latest information on the role of the eCB system in emotionality and anxiety-related disorders throughout the lifespan. Putative therapeutic strategies based on the pharmacological modulation of this system will be discussed. Given the fact that the pharmacological modulation of the eCB system has recently arisen as a promising strategy in the management of anxiety and mood disorders, the potential efficacy of this pharmacological approach (i.e. blockers of the catabolic pathway) will be discussed, as well as pharmacological alternatives such as modulators of cannabinoid receptors other than the classical CB1 receptor, or administration of other plant-derived compounds (e.g. cannabidiol).

The cannabinergic system is implicated in the upregulation of central NGF protein by psychotropic drugs

RATIONALE

Studies on the regulation of nerve growth factor (NGF) levels by psychotropics are limited in scope and the mechanism(s) remain elusive which merit further elucidation.

OBJECTIVES

We aimed to perform a more comprehensive investigation on the possible effects of pharmacologically heterogeneous groups of psychotropic drugs on NGF contents in the brain regions involved in the modulation of emotions. As a mechanistic approach, we looked at the role of the cannabinergic system which is linked to depression and/or antidepressant effect and appears to interact with neurotrophin signaling.

METHODS

Following psychotropic treatment, NGF or endocannabinoid (eCB) contents were quantified by Bio-Rad protein assay and isotope-dilution liquid chromatography/mass spectrometry, respectively. In case of any significant change, the effects of pretreatment with the CB(1) receptor neutral antagonist AM4113 were investigated.

RESULTS

Single injection of nortriptyline, isocarboxazid, citalopram, diazepam, risperidone (2.5, 5, and 10 mg/kg, each), and fluphenazine (0.25, 0.5, and 1 mg/kg) into rats did not alter NGF or eCB contents. Following 4-week treatment, all drugs except diazepam elevated NGF or eCB levels in dose-dependent and brain region-specific fashion. Pretreatment with the highest dose of AM4113 (5.6 mg/kg) prevented psychotropic-induced NGF or eCB elevation. AM4113 had no effect by itself.

CONCLUSIONS

The cannabinergic system is implicated in the mechanisms of action of certain psychotropic drugs including the upregulation of brain NGF levels. This provides a better understanding of the pathophysiological mechanisms underlying neuropsychiatric disorders, leading to novel drug design.

Is lipid signaling through cannabinoid 2 receptors part of a protective system?

The mammalian body has a highly developed immune system which guards against continuous invading protein attacks and aims at preventing, attenuating or repairing the inflicted damage. It is conceivable that through evolution analogous biological protective systems have been evolved against non-protein attacks. There is emerging evidence that lipid endocannabinoid signaling through cannabinoid 2 (CB₂) receptors may represent an example/part of such a protective system/armamentarium. Inflammation/tissue injury triggers rapid elevations in local endocannabinoid levels, which in turn regulate signaling responses in immune and other cells modulating their critical functions. Changes in endocannabinoid levels and/or CB₂ receptor expressions have been reported in almost all diseases affecting humans, ranging from cardiovascular, gastrointestinal, liver, kidney, neurodegenerative, psychiatric, bone, skin, autoimmune, lung disorders to pain and cancer, and modulating CB₂ receptor activity holds tremendous therapeutic potential in these pathologies. While CB₂ receptor activation in general mediates immunosuppressive effects, which limit inflammation and associated tissue injury in large number of pathological conditions, in some disease states activation of the CB₂ receptor may enhance or even trigger tissue damage, which will also be discussed alongside the protective actions of the CB₂ receptor stimulation with endocannabinoids or synthetic agonists, and the possible biological mechanisms involved in these effects.

Deficiency in endocannabinoid signaling in the nucleus accumbens induced by chronic unpredictable stress

The nucleus accumbens (NAc) is a critical component of the reward circuitry, and dysfunction of the NAc may account for anhedonia and other symptoms of depression. Here, we investigated whether alterations in endocannabinoid (eCB) signaling in the NAc contribute to depression-like behaviors induced by chronic unpredictable stress (CUS) in mice. We compared three types of eCB/CB1 receptor-mediated synaptic plasticity in slices prepared from the NAc core of control and stress-exposed mice: depolarization-induced suppression of excitation, long-term depression, and the depression of field excitatory postsynaptic potentials (fEPSPs) induced by group I metabotropic glutamate receptor agonist DHPG. CUS (5-6-week exposure to stressors), but not sub-CUS (1 week exposure to stressors), induces depression-like behaviors and impairs these forms of eCB/CB1 receptor-mediated plasticity examined in the NAc core. Neither sub-CUS nor CUS altered the tissue contents of the eCBs, anandamide and 2-arachidonoylglycerol in the striatum. However, exposure to CUS, but not to sub-CUS, attenuated the depression of fEPSPs induced by the CB1 receptor agonist WIN 55 212-2. CUS exposure reduced the maximal effect without affecting the EC(50) of WIN 55 212-2 to induce fEPSP depression. Thus, impaired CB1 receptor function could account for CUS-induced deficiency in eCB signaling in the NAc. Both CUS-induced deficiency in eCB signaling and depression-like behaviors were reversed by in vivo administration of antidepressant fluoxetine. These results suggest that downregulation of eCB signaling in the NAc occurs after CUS and contributes to the pathophysiology of depression.

Cannabinoid CB1 receptor immunoreactivity in the prefrontal cortex: Comparison of schizophrenia and major depressive disorder

We recently showed that measures of cannabinoid 1 receptor (CB1R) mRNA and protein were significantly reduced in dorsolateral prefrontal cortex (DLPFC) area 9 in schizophrenia subjects relative to matched normal comparison subjects. However, other studies have reported unaltered or higher measures of CB1R levels in schizophrenia. To determine whether these discrepancies reflect differences across brain regions or across subject groups (eg, presence of depression, cannabis exposure, etc), we used immunocytochemical techniques to determine whether lower levels of CB1R immunoreactivity are (1) present in another DLPFC region, area 46, in the same subjects with schizophrenia, (2) present in area 46 in a new cohort of schizophrenia subjects, (3) present in major depressive disorder (MDD) subjects, or (4) attributable to factors other than a diagnosis of schizophrenia, including prior cannabis use. CB1R immunoreactivity levels in area 46 were significantly 19% lower in schizophrenia subjects relative to matched normal comparison subjects, a deficit similar to that observed in area 9 in the same subjects. In a new cohort of subjects, CB1R immunoreactivity levels were significantly 20 and 23% lower in schizophrenia subjects relative to matched comparison and MDD subjects, respectively. The lower levels of CB1R immunoreactivity in schizophrenia subjects were not explained by other factors such as cannabis use, suicide, or pharmacological treatment. In addition, CB1R immunoreactivity levels were not altered in monkeys chronically exposed to haloperidol. Thus, the lower levels of CB1R immunoreactivity may be common in schizophrenia, conserved across DLPFC regions, not present in MDD, and not attributable to other factors, and thus a reflection of the underlying disease process.

Cannabinoids and Dementia: A Review of Clinical and Preclinical Data

The endocannabinoid system has been shown to be associated with neurodegenerative diseases and dementia. We review the preclinical and clinical data on cannabinoids and four neurodegenerative diseases: Alzheimer’s disease (AD), Huntington’s disease (HD), Parkinson’s disease (PD) and vascular dementia (VD). Numerous studies have demonstrated an involvement of the cannabinoid system in neurotransmission, neuropathology and neurobiology of dementias. In addition, several candidate compounds have demonstrated efficacy in vitro. However, some of the substances produced inconclusive results in vivo. Therefore, only few trials have aimed to replicate the effects seen in animal studies in patients. Indeed, the literature on cannabinoid administration in patients is scarce. While preclinical findings suggest causal treatment strategies involving cannabinoids, clinical trials have only assessed the suitability of cannabinoid receptor agonists, antagonists and cannabidiol for the symptomatic treatment of dementia. Further research is needed, including in vivo models of dementia and human studies.

Brain CB₂ Receptors: Implications for Neuropsychiatric Disorders

Although previously thought of as the peripheral cannabinoid receptor, it is now accepted that the CB₂ receptor is expressed in the central nervous system on microglia, astrocytes and subpopulations of neurons. Expression of the CB₂ receptor in the brain is significantly lower than that of the CB₁ receptor. Conflicting findings have been reported on the neurological effects of pharmacological agents targeting the CB₂ receptor under normal conditions. Under inflammatory conditions, CB₂ receptor expression in the brain is enhanced and CB₂ receptor agonists exhibit potent anti-inflammatory effects. These findings have prompted research into the CB₂ receptor as a possible target for the treatment of neuroinflammatory and neurodegenerative disorders. Neuroinflammatory alterations are also associated with neuropsychiatric disorders and polymorphisms in the CB₂ gene have been reported in depression, eating disorders and schizophrenia. This review will examine the evidence to date for a role of brain CB₂ receptors in neuropsychiatric disorders.

Selective alterations of the CB1 receptors and the fatty acid amide hydrolase in the ventral striatum of alcoholics and suicides

Recent studies in rodents have suggested a role for the central endocannabinoid system in the regulation of mood and alcohol related behaviors. Alcohol use disorder is often associated with suicidal behavior. In the present study, we examined whether abnormalities in the endocannabinoid system in the ventral striatum are associated with alcohol dependence and suicide. The levels of CB1 receptors, receptor-mediated G-protein signaling, and activity and level of the fatty acid amide hydrolase (FAAH) were analyzed postmortem in the ventral striatum of alcohol-dependent nonsuicides (CA, n=9), alcohol-dependent suicides (AS, n=9) and nonpsychiatric controls (C, n=9). All subjects underwent a psychological autopsy, and toxicological and neuropathological examinations. The levels of the CB1 receptors and the CB1 receptor-mediated G-protein signaling were significantly lower in the ventral striatum of CA compared to the control group. However, these parameters were elevated in AS when compared to CA group. The activity of FAAH enzyme was lower in CA compared to the control group while it was found to be significantly higher in AS compared with CA group. These findings suggest that alcohol dependence is associated with the downregulation of the CB1 receptors, while suicide is linked to the upregulation of these receptors in the ventral striatum. Alteration in the activity of FAAH enzyme that regulates the anandamide (AEA) content might in turn explain differences in the CB1 receptor function in alcohol dependence and suicide. These findings may have etiological and therapeutic implications for the treatment of alcohol addiction and suicidal behavior.

Inhibition of monoamine oxidase activity by cannabinoids

Brain monoamines are involved in many of the same processes affected by neuropsychiatric disorders and psychotropic drugs, including cannabinoids. This study investigated in vitro effects of cannabinoids on the activity of monoamine oxidase (MAO), the enzyme responsible for metabolism of monoamine neurotransmitters and affecting brain development and function. The effects of the phytocannabinoid Delta(9)-tetrahydrocannabinol (THC), the endocannabinoid anandamide (N-arachidonoylethanolamide [AEA]), and the synthetic cannabinoid receptor agonist WIN 55,212-2 (WIN) on the activity of MAO were measured in a crude mitochondrial fraction isolated from pig brain cortex. Monoamine oxidase activity was inhibited by the cannabinoids; however, higher half maximal inhibitory concentrations (IC(50)) of cannabinoids were required compared to the known MAO inhibitor iproniazid. The IC(50) was 24.7 micromol/l for THC, 751 micromol/l for AEA, and 17.9 micromol/l for WIN when serotonin was used as substrate (MAO-A), and 22.6 micromol/l for THC, 1,668 micromol/l for AEA, and 21.2 micromol/l for WIN when phenylethylamine was used as substrate (MAO-B). The inhibition of MAOs by THC was noncompetitive. N-Arachidonoylethanolamide was a competitive inhibitor of MAO-A and a noncompetitive inhibitor of MAO-B. WIN was a noncompetitive inhibitor of MAO-A and an uncompetitive inhibitor of MAO-B. Monoamine oxidase activity is affected by cannabinoids at relatively high drug concentrations, and this effect is inhibitory. Decrease of MAO activity may play a role in some effects of cannabinoids on serotonergic, noradrenergic, and dopaminergic neurotransmission.

Subjective effects of cannabis before the first psychotic episode

OBJECTIVE

The aim of the present study was to gain more insight into the positive and negative effects of cannabis in the prodromal phase of schizophrenia and in the ultra-high-risk (UHR) state for psychosis.

METHOD

A theory-driven questionnaire was used to examine subjective effects in the prodromal phase in male subjects with a recent onset of schizophrenia or related disorder (n = 52) and in the UHR state in help-seeking male subjects screened for being at UHR for psychosis (n = 17); both groups were compared to cannabis-using controls from the general population (n=52).

RESULTS

Recent-onset patients and UHR subjects reported feeling more anxious, depressed and suspicious immediately after cannabis use. Some patients also reported feeling less depressed after cannabis use. Recent-onset patients reported increased visual and acoustic hallucinations, and confusion after cannabis use. Of the recent-onset patients 37% reported that their very first psychotic symptoms occurred during cannabis intoxication. Long-term effects of cannabis reported more often by both patient groups were depression, less control over thoughts and social problems.

CONCLUSIONS

These results suggest that schizophrenia patients in the prodromal phase and subjects at UHR for psychosis are more sensitive to some negative effects of cannabis, in particular psychotic effects, compared to cannabis users from the general population. Although limited by the retrospective design in the recent-onset patients, the present study adds qualitative evidence to longitudinal studies that suggest that cannabis is a component cause in the onset of the first psychotic episode. Further studies are needed on the objective and subjective effects of cannabis in UHR subjects.

The endocannabinoid system and the regulation of neural development: potential implications in psychiatric disorders

During brain development, functional neurogenesis is achieved by the concerted action of various steps that include the expansion of progenitor cells, neuronal specification, and establishment of appropriate synapses. Brain patterning and regionalization is regulated by a variety of extracellular signals and morphogens that, together with neuronal activity, orchestrate and regulate progenitor proliferation, differentiation, and neuronal maturation. In the adult brain, CB(1) cannabinoid receptors are expressed at very high levels in selective areas and are engaged by endocannabinoids, which act as retrograde messengers controlling neuronal function and preventing excessive synaptic activity. In addition, the endocannabinoid system is present at early developmental stages of nervous system formation. Recent studies have provided novel information on the role of this endogenous neuromodulatory system in the control of neuronal specification and maturation. Thus, cannabinoid receptors and locally produced endocannabinoids regulate neural progenitor proliferation and pyramidal specification of projecting neurons. CB(1) receptors also control axonal navigation, migration, and positioning of interneurons and excitatory neurons. Loss of function studies by genetic ablation or pharmacological blockade of CB(1) receptors interferes with long-range subcortical projections and, likewise, prenatal cannabinoid exposure induces different functional alterations in the adult brain. Potential implications of these new findings, such as the participation of the endocannabinoid system in the pathogenesis of neurodevelopmental disorders (e.g., schizophrenia) and the regulation of neurogenesis in brain depression, are discussed herein.

Altered responses of dopamine D3 receptor null mice to excitotoxic or anxiogenic stimuli: Possible involvement of the endocannabinoid and endovanilloid systems

Dopamine and the endocannabinoids, anandamide and 2-arachidonoylglycerol, interact at several levels in the brain, with the involvement of both cannabinoid CB(1) receptors and transient receptor potential vanilloid type-1 (TRPV1) channels (which are alternative anandamide receptors). Using pharmacological, immunohistochemical and analytical approaches, we investigated the response of dopamine D(3) receptor null (D3R((-/-))) mice in models of epilepsy and anxiety, in relation to their brain endocannabinoid and endovanilloid tone. Compared to wild-type mice, D3R((-/-)) mice exhibited a delayed onset of clonic seizures, enhanced survival time, reduced mortality rate and more sensitivity to anticonvulsant effects of diazepam after intraperitoneal administration of picrotoxin (7 mg/kg), and a less anxious-like behaviour in the elevated plus maze test. D3R((-/-)) mice also exhibited different endocannabinoid and TRPV1, but not CB(1), levels in the hippocampus, nucleus accumbens, amygdala and striatum. Given the role played by CB(1) and TRPV1 in neuroprotection and anxiety, and based on data obtained here with pharmacological tools, we suggest that the alterations of endocannabinoid and endovanilloid tone found in D3R((-/-)) mice might account for part of their altered responses to excitotoxic and anxiogenic stimuli.

In vivo pharmacology of endocannabinoids and their metabolic inhibitors: therapeutic implications in Parkinson's disease and abuse liability

This review focuses on the behavioral pharmacology of endogenous cannabinoids (endocannabinoids) and indirect-acting cannabinoid agonists that elevate endocannabinoid tone by inhibiting the activity of metabolic enzymes. Similarities and differences between prototype cannabinoid agonists, endocannabinoids and inhibitors of endocannabinoid metabolism are discussed in the context of endocannabinoid pharmacokinetics in vivo. The distribution and function of cannabinoid and non-CB(1)/CB(2) receptors are also covered, with emphasis on their role in disorders characterized by dopamine dysfunction, such as drug abuse and Parkinson's disease. Finally, evidence is presented to suggest that FAAH inhibitors lack the abuse liability associated with CB(1) agonists, although they may modify the addictive properties of other drugs, such as alcohol.

Protracted cannabinoid administration elicits antidepressant behavioral responses in rats: role of gender and noradrenergic transmission

Research has shown that enhancement of cannabinoid CB(1) receptor activity elicits an antidepressant-like response in the forced swim test (FST); however, the effects of chronic administration of cannabinoid agents in the FST are not well characterized. In Experiment 1, the CB(1) receptor agonist HU-210 (0.1 mg/kg) was administered for 10 days to male rats, following which animals were exposed to the FST. In Experiment 2, the same protocol was utilized; however, prior to the FST animals were co-treated with either prazosin (1 mg/kg; an alpha(1)-adrenoreceptor antagonist) or propranolol (2.5 mg/kg; a beta-adrenoreceptor antagonist). In Experiment 3, the same protocol was employed in both male and female rats, and the role of drug withdrawal was examined by administration of the CB(1) receptor antagonist AM251 (1 mg/kg) prior to the FST. Experiment 1 revealed that HU-210 administration evoked a reduction in immobility and increase in struggling that was identical to that produced by the antidepressant desipramine (10 mg/kg). Experiment 2 revealed that this effect was attenuated by both alpha- and beta-adrenoreceptor antagonists, suggesting noradrenergic involvement in this antidepressant-like profile. Experiment 3 demonstrated that HU-210 administration produced an antidepressant response in both males and females, which was attenuated by the induction of precipitated withdrawal. These results show that protracted administration of a CB(1) receptor agonist produces an antidepressant-like response in the FST in both sexes, which appears to involve the noradrenergic system.

Quantitative and qualitative profiling of endocannabinoids in human plasma using a triple quadrupole linear ion trap mass spectrometer with liquid chromatography

Owing to the large implication of endocannabinoids (ECs) in many physiological and pathophysiological processes, a rapid liquid chromatography/electrospray ionisation triple quadrupole linear ion trap mass spectrometric assay (LC/ESI-QqQ(LIT)) was developed for the detection and characterization of anandamide (AEA), 2-arachidonoyl glycerol (2-AG), virodhamine (VA), noladin ether (2-AGE), and N-arachidonoyl dopamine (NADA) in human plasma. The ECs were extracted from 500 microL of plasma by liquid-liquid extraction (LLE) and separated by using an XTerra C18 MS column (50 x 3.0 mm i.d., 3.5 microm) with gradient elution. The mobile phase was composed of a mixture of acetonitrile, water, and formic acid (0.1%). For confirmatory analysis, an information-dependent acquisition (IDA) experiment was performed with selected reaction monitoring (SRM) as survey scan and enhanced product ion (EPI) as dependent scan. The assay was found to be linear in the concentration range of 0.1-5 ng/mL for AEA, 0.3-5 ng/mL for VA, 2-AGE, and NADA and 1-20 ng/mL for 2-AG using a 0.5 mL aliquot of plasma. Repeatability and intermediate precision were found less than 15% over the tested concentration ranges. The developed method thus provided the rapid, highly sensitive and highly selective requirement for assess quantitation, and identification of ECs in plasma.

Differential effects of the antidepressants tranylcypromine and fluoxetine on limbic cannabinoid receptor binding and endocannabinoid contents

The goal of this study was to determine whether the endocannabinoid system is altered by chronic antidepressant treatment. The effects of 3-week administration of the monoamine oxidase inhibitor, tranylcypromine (10 mg/kg) and the selective serotonin reuptake inhibitor, fluoxetine (5 mg/kg) on cannabinoid CB(1) receptor densities and endocannabinoid contents were determined in limbic brain regions of the rat. Tranylcypromine significantly reduced tissue content of the endocannabinoid N-arachidonylethanolamine (anandamide) in the prefrontal cortex, hippocampus and hypothalamus and increased 2-arachidonoylglycerol content in the prefrontal cortex. Tranylcypromine treatment significantly increased CB(1) receptor binding density in the prefrontal cortex and hippocampus, but not in the hypothalamus. Treatment with fluoxetine increased CB(1) receptor density in the prefrontal cortex, but had no effect on endocannabinoid contents in any brain region examined. These data suggest that monoaminergic neurotransmission can regulate the endocannabinoid system and further indicates a role of the endocannabinoid system in affective illness and its treatment.

Regional alterations in the endocannabinoid system in an animal model of depression: effects of concurrent antidepressant treatment

It has been suggested that disturbances in endocannabinoid signaling contribute to the development of depressive illness; however, at present there is insufficient evidence to allow for a full understanding of this role. To further this understanding, we performed an analysis of the endocannabinoid system in an animal model of depression. Male rats exposed to chronic, unpredictable stress (CUS) for 21 days exhibited a reduction in sexual motivation, consistent with the hypothesis that CUS in rats induces depression-like symptoms. We determined the effects of CUS, with or without concurrent treatment with the antidepressant imipramine (10 mg/kg), on CP55940 binding to the cannabinoid CB(1) receptor; whole tissue endocannabinoid content; and fatty acid amide hydrolase (FAAH) activity in the prefrontal cortex, hippocampus, hypothalamus, amygdala, midbrain and ventral striatum. Exposure to CUS resulted in a significant increase in CB(1) receptor binding site density in the prefrontal cortex and a decrease in CB(1) receptor binding site density in the hippocampus, hypothalamus and ventral striatum. Except in the hippocampus, these CUS-induced alterations in CB(1) receptor binding site density were attenuated by concurrent antidepressant treatment. CUS alone produced a significant reduction in N-arachidonylethanolamine (anandamide) content in every brain region examined, which was not reversed by antidepressant treatment. These data suggest that the endocannabinoid system in cortical and subcortical structures is differentially altered in an animal model of depression and that the effects of CUS on CB(1) receptor binding site density are attenuated by antidepressant treatment while those on endocannabinoid content are not.

Neurobiological mechanisms of cannabinoid addiction

The endocannabinoid system is implicated in the regulation of a variety of physiological processes, among which conditioning, motivation, habit forming, memory, learning, and cognition play pivotal roles in drug reinforcement and reward. In this article we will give a synopsis of last developments in research on cannabinoid actions on brain reward circuits coming from behavioral, neurochemical and electrophysiological studies. Central cannabinoid-induced effects as measured by animal models of addiction, in vivo cerebral microdialysis, in vitro and in vivo electrophysiological recording techniques, will be reviewed. Brain sites that have been implicated in the mediation of addictive cannabinoid properties include primarily the ventral tegmental area, the nucleus accumbens, and the medial prefrontal cortex, although the amygdala, the substantia nigra, the globus pallidus, and the hippocampus have also been shown to be critical structures mediating motivational and reinforcing effects of cannabinoids. Putative neurobiological mechanisms underlying these effects will be delineated.