The cannabinoid CB1receptor and the endocannabinoid anandamide: possible antidepressant targets

The Chronic Pharmacological Antagonism of the CB1 Receptor is not Involved in the Behavioral Effects of Antidepressants Administered in Mice Submitted to Chronic Unpredictable Stress

Several pieces of evidence suggest that the monoaminergic theory of depression cannot fully explain all behavioral and neuroplastic changes observed after antidepressant chronic treatment. Other molecular targets, such as the endocannabinoid system, have been associated with the chronic effects of these drugs. In the present study, we hypothesized that the behavioral and neuroplastic effects observed after repeated treatment with the antidepressants (AD) Escitalopram (ESC) or venlafaxine (VFX) in chronically stressed mice depend on CB1 receptor activation. Male mice submitted to the chronic unpredictable stress (CUS) paradigm for 21 days were treated with Esc (10mg/kg) or VFX (20mg/kg) once a day in the presence or not of AM251 (0,3mg/kg), a CB₁ receptor antagonist/inverse agonist. At the end of the CUS paradigm, we conducted behavior tests to evaluate depressive- and anxiety-like behaviors. Our results demonstrated that chronic blockade of the CB₁ receptor does not attenuate the antidepressant- or the anxiolytic-like effects of ESC nor VFX. ESC increased the expression of CB₁ in the hippocampus, but AM251 did not change the pro-proliferative effects of ESC in the dentate gyrus or the increased expression of synaptophysin induced by this AD in the hippocampus. Our results suggest that CB₁ receptors are not involved in behavioral and hippocampal neuroplastic effects observed after repeated antidepressant treatment in mice submitted to CUS.

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

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

In vivo brain endocannabinoid metabolism is related to hippocampus glutamate and structure - a multimodal imaging study with PET, 1H-MRS, and MRI

Dysregulation of hippocampus glutamatergic neurotransmission and reductions in hippocampal volume have been associated with psychiatric disorders. The endocannabinoid system modulates glutamate neurotransmission and brain development, including hippocampal remodeling. In humans, elevated levels of anandamide and lower activity of its catabolic enzyme fatty acid amide hydrolase (FAAH) are associated with schizophrenia diagnosis and psychotic symptom severity, respectively (Neuropsychopharmacol, 29(11), 2108-2114; Biol. Psychiatry 88 (9), 727-735). Although preclinical studies provide strong evidence linking anandamide and FAAH to hippocampus neurotransmission and structure, these relationships remain poorly understood in humans. We recruited young adults with and without psychotic disorders and measured FAAH activity, hippocampal glutamate and glutamine (Glx), and hippocampal volume using [11C]CURB positron emission tomography (PET), proton magnetic resonance spectroscopy (1H-MRS) and T1-weighted structural MRI, respectively. We hypothesized that higher FAAH activity would be associated with greater hippocampus Glx and lower hippocampus volume, and that these effects would differ in patients with psychotic disorders relative to healthy control participants. After attrition and quality control, a total of 37 participants (62% male) completed [11C]CURB PET and 1H-MRS of the left hippocampus, and 45 (69% male) completed [11C]CURB PET and hippocampal volumetry. Higher FAAH activity was associated with greater concentration of hippocampal Glx (F1,36.36 = 9.17, p = 0.0045; Cohen's f = 0.30, medium effect size) and smaller hippocampal volume (F1,44.70 = 5.94, p = 0.019, Cohen's f = 0.26, medium effect size). These effects did not differ between psychosis and healthy control groups (no group interaction). This multimodal imaging study provides the first in vivo evidence linking hippocampal Glx and hippocampus volume with endocannabinoid metabolism in the human brain.

Cannabinoids—Perspectives for Individual Treatment in Selected Patients: Analysis of the Case Series

Cannabinoids can be successfully used in the treatment of many symptoms and diseases; however, most often they are not the drugs of first choice. They can be added to the primary therapy, which can improve its effectiveness, or be introduced as the basic treatment when the conventional methods have failed. Small clinical trials and case reports prove the benefits of applying medicinal cannabis in various indications; however, clinical trials in larger groups of patients are scarce and often controversial. Due to limited scientific evidence, it is essential to conduct further experimental trials. Understanding the role of endocannabinoids, as well as the composition of cannabis containing both phytocannabinoids and terpenes plays an important role in their clinical use. The clinical effects of cannabinoids depend, among other things, on the activity of the endocannabinoid system, the proportion of phytocannabinoids, such as Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD), and the dosage used. The article discusses the role of phytocannabinoids and the potential of using them in different clinical cases in patients suffering from chronic pain, opioid dependence, depression and migraine, who did not respond to the conventional therapeutic methods. In each of the presented cases, the implementation of cannabinoids altered the course of the disease and resulted in symptom relief. Every decision to introduce cannabinoids to the treatment should be made individually with careful attention paid to details. Additionally, it is worth taking care of good clinical communication and education so that the implemented therapy is safe, effective and properly perceived by the patient.

Rapid treatments for depression: Endocannabinoid system as a therapeutic target

Current first-line treatments for major depressive disorder (MDD), i.e., antidepressant drugs and psychotherapy, show delayed onset of therapeutic effect as late as 2-3 weeks or more. In the clinic, the speed of beginning of the actions of antidepressant drugs or other interventions is vital for many reasons. Late-onset means that depression, its related disability, and the potential danger of suicide remain a threat for some patients. There are some rapid-acting antidepressant interventions, such as sleep deprivation, ketamine, acute exercise, which induce a significant response, ranging from a few hours to maximally one week, and most of them share a common characteristic that is the activation of the endocannabinoid (eCB) system. Activation of this system, i.e., augmentation of eCB signaling, appears to have anti-depressant-like actions. This article puts the idea forward that the activation of eCB signaling represents a critical mechanism of rapid-acting therapeutic interventions in MDD, and this system might contribute to the development of novel rapid-acting treatments for MDD.

Antidepressant action of transcranial direct current stimulation in olfactory bulbectomised adolescent rats

BACKGROUND

Antidepressant drugs in adolescent depression are sometimes mired by efficacy issues and paradoxical effects. Transcranial direct current stimulation (tDCS) could represent an alternative.

AIMS/METHODS

We tested the antidepressant action of prefrontal tDCS and paroxetine (20 mg/kg, intraperitoneal) in olfactory bulbectomised (OBX) adolescent rats. Using enzyme-linked immunosorbent assays and in situ hybridisation, we examined treatment-induced changes in plasma brain-derived neurotrophic factor (BDNF) and brain serotonin transporter (SERT) and 5-HT-1A mRNA.

RESULTS

OBX-induced anhedonia-like reductions in sucrose preference (SP) correlated with open field (OF) hyperactivity. These were accompanied by decreased zif268 mRNA in the piriform/amygdalopiriform transition area, and increased zif268 mRNA in the hypothalamus. Acute paroxetine (2 days) led to a profound SP reduction, an effect blocked by combined tDCS-paroxetine administration. Chronic (14 days) tDCS attenuated hyperlocomotion and its combination with paroxetine blocked OBX-induced SP reduction. Correlations among BDNF, SP and hyperlocomotion scores were altered by OBX but were normalised by tDCS-paroxetine co-treatment. In the brain, paroxetine increased zif268 mRNA in the hippocampal CA1 subregion and decreased it in the claustrum. This effect was blocked by tDCS co-administration, which also increased zif268 in CA2. tDCS-paroxetine co-treatment had variable effects on 5-HT1A receptors and SERT mRNA. 5-HT1A receptor changes were found exclusively within depression-related parahippocampal/hippocampal subregions, and SERT changes within fear/defensive response-modulating brainstem circuits.

CONCLUSION

These findings point towards potential synergistic efficacies of tDCS and paroxetine in the OBX model of adolescent depression via mechanisms associated with altered expression of BDNF, 5-HT1A, SERT and zif268 in discrete corticolimbic areas.

Cannabinoids and sleep-wake cycle: The potential role of serotonin

Cannabis sativa (Marijuana) has a long history as a medicinal plant and Δ9-tetrahydrocannabinol (Δ9-THC) is the most active component in this plant. Cannabinoids are interesting compounds with various modulatory effects on physiological processes and cognitive functions. The use of cannabinoids is a double-edged sword, because they induce both adverse and therapeutic properties. One of the most important roles of cannabinoids is modulating sleep-wake cycle. Sleep, its cycle, and its mechanism are highly unknown. Also, the effects of cannabinoids on sleep-wake cycle are so inconsistent. Thus, understanding the role of cannabinoids in modulating sleep-wake cycle is a critical scientific goal. Cannabinoids interact with many neurotransmitter systems. In this review article, we chose serotonin due to its important role in regulating sleep-wake cycle. We found that the interaction between cannabinoids and serotonergic signaling especially in the dorsal raphe is extensive, unknown, and controversial.

From an Alternative Medicine to a New Treatment for Refractory Epilepsies: Can Cannabidiol Follow the Same Path to Treat Neuropsychiatric Disorders?

Although cannabis has been known for ages as an "alternative medicine" to provide relief from seizures, pain, anxiety, and inflammation, there had always been a limited scientific review to prove and establish its use in clinics. Early studies carried out by Carlini's group in Brazil suggested that cannabidiol (CBD), a non-psychotropic phytocannabinoid present in Cannabis sativa, has anticonvulsant properties in animal models and reduced seizure frequency in limited human trials. Over the past few years, the potential use of cannabis extract in refractory epilepsy, including childhood epilepsies such as Dravet's syndrome and Lennox-Gastaut Syndrome, has opened a new era of treating epileptic patients. Thus, a considerable number of pre-clinical and clinical studies have provided strong evidence that phytocannabinoids has anticonvulsant properties, as well as being promising in the treatment of different neuropsychiatric disorders, such as depression, anxiety, post-traumatic stress disorder (PTSD), addiction, neurodegenerative disorders and autism spectrum disorder (ASD). Given the advances of cannabinoids, especially CBD, in the treatment of epilepsy, would the same expectation regarding the treatment of other neuropsychiatric disorders be possible? The present review highlights some contributions from Brazilian researchers and other studies reported elsewhere on the history, pre-clinical and clinical data underlying the use of cannabinoids for the already widespread treatment of refractory epilepsies and the possibility of use in the treatment of some neuropsychiatric disorders.

Integrating Endocannabinoid Signalling In Depression

Depression is a common mental disorder and is the leading cause of suicide globally. Because of the significant diversity in mental disorders, accurate diagnosis is difficult. Hence, the investigation of novel biomarkers is a key research perspective in psychotherapy to enable an individually tailored treatment approach. The prefrontal cortex (PFC) is a vital cortical region whose circuitry has been implicated in the development of depressive disorder. The endocannabinoid system (ECS) has garnered increasing attention because of its involvement in several diverse physiological brain processes including regulation of emotional, motivational and cognitive functions. The current review article explores the function of the key elements of the ECS as a biomarker in depressive disorder. The activity of endocannabinoids is thought to be moderated by the CB1 receptors in the central nervous system (CNS). Variations in the concentration of endocannabinoids and the binding affinity of CB1 receptors and their density have been identified in the PFC of persons with depression. Such discoveries support our theory that alteration in endocannabinoid function leads to the pathophysiological features of depressive disorders. Moreover, evidence from animal and human studies has revealed that dysfunction in endocannabinoid signalling can produce depression-like behaviours; therefore, improvement of endocannabinoid signalling may represent a new therapeutic approach for the management of depressive disorders.

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.

Solid lipid nanoparticles loading with curcumin and dexanabinol to treat major depressive disorder

Dexanabinol (HU-211) is an artificially synthesized cannabinoid derivative that exerts neuroprotective effects through anti-inflammatory and antioxidant effects. Curcumin exhibits antidepressant effects in the treatment of major depressive disorder. To investigate the antidepressant effects of solid lipid nanoparticles loaded with both curcumin and dexanabinol, and the underlying mechanisms associated with this combination, we established wild-type (CBR1^+/+) and cannabinoid receptor 1 (CBR1) knockout (CBR1^–/–) mouse models of major depressive disorder, through the intraperitoneal injection of corticosterone, for 3 successive days, followed by treatment with intraperitoneal injections of solid lipid nanoparticles loading with curcumin (20 mg/kg) and dexanabinol (0.85 mg/kg), for 2 successive days. Our results revealed that solid lipid nanoparticle loading with curcumin and dexanabinol increased the mRNA and protein expression levels of the mature neuronal markers neuronal nuclei, mitogen-activated protein 2, and neuron-specific beta-tubulin III, promoted the release of dopamine and norepinephrine, and increased the mRNA expression of CBR1 and the downstream genes Rasgef1c and Egr1, and simultaneously improved rat locomotor function. However, solid lipid nanoparticles loaded with curcumin and dexanabinol had no antidepressant effects on the CBR1^–/– mouse models of major depressive disorder. This study was approved by the Institutional Ethics Committee of Tongji Hospital of Tongji University, China (approval No. 2017-DW-020) on May 24, 2017.

Prospects for the Use of Cannabinoids in Psychiatric Disorders

Increasing evidence suggests an essential role of the endocannabinoid system in modulating cognitive abilities, mood, stress, and sleep. The psychoactive effects of cannabis are described as euphoric, calming, anxiolytic, and sleep-inducing and positively affect the mood, but can also adversely affect therapy. The responses to cannabinoid medications depend on the patient's endocannabinoid system activity, the proportion of phytocannabinoids, the terpenoid composition, and the dose used. There is some evidence for a therapeutic use of phytocannabinoids in psychiatric conditions. THC and CBD may have opposing effects on anxiety. Current guidelines recommend caution in using THC in patients with anxiety or mood disorders. In a small number of clinical trials, cannabinoids used to treat cancer, HIV, multiple sclerosis, hepatitis C, Crohn's disease, and chronic neuropathic pain report decreases in anxiety or depression symptoms and presented sedative and anxiolytic effects. Several studies have investigated the influence of potential genetic factors on psychosis and schizophrenia development after cannabis use. THC may increase the risk of psychosis, especially in young patients with an immature central nervous system. There is limited evidence from clinical trials that cannabinoids are effective therapy for sleep disorders associated with concomitant conditions. There is evidence for a possible role of cannabis as a substitute for alcohol and drugs, also in the context of the risks of opioid use (e.g., opioid-related mortality). In this narrative review of the recent evidence, we discuss the prospects of using the psychoactive effects of cannabinoids in treating mental and psychiatric disorders. However, this evidence is weak for some clinical conditions and well-designed randomized controlled trials are currently lacking. Furthermore, some disorders may be worsened by cannabis use.

Moderating role of cannabis use between insight and depression in early psychosis

BACKGROUND

A high level of insight in first episode psychosis (FEP) is positively correlated to important prognostic factors such as medication adherence and functional outcome but is associated with increased depression level and suicidal behavior.

AIMS

This is the first study questioning the potential moderating role of cannabis use in the relationship between insight and depression one year after a FEP.

METHOD

In this prospective observational study, we enrolled 214 FEP patients who had provided informed consent and been referred to a specialized early psychosis program and followed for 36 months. A series of multivariate regression models were used. Baseline insight, medication adherence and cannabis use (level of use on a continuum) were entered as independent variables, while the PANSS (positive and negative), the MADRS and the SOFAS scores after one year were alternately selected as the dependent variable.

RESULTS

We found a three-way interaction term between cannabis use, insight and medication adherence on depression level one year after the entry into the program. A high level of insight was significantly associated with higher MADRS scores in patients with high cannabis use, while depression decreased in high-insight patients with low cannabis use.

CONCLUSIONS

Cannabis use continuation during the year following a first episode psychosis may play a significant role in the development or the maintenance of post-psychotic depression in patients who present with high level of insight and adherence to medication, stressing the need for specific therapeutic strategies in this subgroup of patients.

Integrating endocannabinoid signaling in the regulation of anxiety and depression

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

Medical and non-medical marijuana use in depression: Longitudinal associations with suicidal ideation, everyday functioning, and psychiatry service utilization

BACKGROUND

Marijuana use is clinically problematic in depression, and non-medical and medical use may both contribute to barriers to care in this population. Among outpatients with depression, we examined the differential impact of medical or non-medical marijuana use, relative to no-use, on psychopathology and service use over time.

METHOD

Participants were 307 psychiatry outpatients participating in a trial of drug/alcohol use treatment for depression. Measures of past 30-day marijuana use, depression/anxiety symptoms, psychiatry visits, and functional data related to health status were collected at baseline, 3, 6, and 12 months. Regressions (baseline and 1 year) and growth models (over time) predicted clinical and psychiatry visit outcomes, from medical or non-medical marijuana use (no-use = reference).

RESULTS

At baseline, 40.0% of the sample used marijuana and more reported non-medical (71.7%) than medical (28.2%) use. Relative to non-users at baseline, patients using medically had worse mental/physical health functioning (p's < 0.05), and non-medical use was associated with higher suicidal ideation (B = 1.08, p = .002), worse mental health functioning (B = -3.79, p = .015), and fewer psychiatry visits (B = -0.69, p = .009). Patients using non-medically over time improved less in depression symptoms (B = 1.49, p = .026) and suicidal ideation (B = 1.08, p = .003) than non-users.

LIMITATIONS

Participants were psychiatry outpatients, limiting generalizability.

CONCLUSIONS

Marijuana use, especially non-medical use, among patients with depression may impede depression symptom improvement while lessening the likelihood of psychiatry visits. Marijuana use and associated barriers to care should receive consideration by depression treatment providers.

Adult Cellular Neuroadaptations Induced by Adolescent THC Exposure in Female Rats Are Rescued by Enhancing Anandamide Signaling

BACKGROUND

In rodent models, chronic exposure to cannabis' psychoactive ingredient, Δ9-tetrahydrocannabinol, during adolescence leads to abnormal behavior in adulthood. In female rats, this maladaptive behavior is characterized by endophenotypes for depressive-like and psychotic-like disorders as well as cognitive deficits. We recently reported that most depressive-like behaviors triggered by adolescent Δ9-tetrahydrocannabinol exposure can be rescued by manipulating endocannabinoid signaling in adulthood with the anandamide-inactivating enzyme FAAH inhibitor, URB597. However, the molecular mechanisms underlying URB597's antidepressant-like properties remain to be established.

METHODS

Here we examined the impact of adult URB597 treatment on the cellular and functional neuroadaptations that occurred in the prefrontal cortex and dentate gyrus of the hippocampus upon Δ9-tetrahydrocannabinol during adolescence through biochemical, morphofunctional, and electrophysiological studies.

RESULTS

We found that the positive action of URB597 is associated with the rescue of Δ9-tetrahydrocannabinol-induced deficits in endocannabinoid-mediated signaling and synaptic plasticity in the prefrontal cortex and the recovery of functional neurogenesis in the dentate gyrus of the hippocampus. Moreover, the rescue property of URB597 on depressive-like behavior requires the activity of the CB1 cannabinoid receptor.

CONCLUSIONS

By providing novel insights into the cellular and molecular mechanisms of URB597 at defined cortical and hippocampal circuits, our results highlight that positive modulation of endocannabinoid-signaling could be a strategy for treating mood alterations secondary to adolescent cannabis use.

Pharmacological characterization of the cannabinoid receptor 2 agonist, β-caryophyllene on seizure models in mice

PURPOSE

Activation of CB1 receptors, produces anticonvulsant effect accompanied by memory disturbance both in animal seizure tests and in patients with epilepsy. Few reports considered the role of CB2 receptor on seizure susceptibility and cognitive functions. The aim of the present study was to explore the effect of a selective CB2 receptor agonist β-caryophyllene (BCP) in models of seizures and cognition in mice.

METHODS

Dose-dependent effects of BCP was studied in maximal electroshock seizure (MES) test, subcutaneous pentylenetetrazole (scPTZ) test and Morris water maze test. Phenytoin and diazepam were used as reference drugs in seizure tests. The effect of sub-chronic treatment with BCP for 7 days (50 and 100 mg kg^-1) was assessed on status epilepticus (SE) induced by kainic acid (KA) model and oxidative stress through measurement of malondialdehyde (MDA) level in the hippocampus. The acute neurotoxicity was determined by a rotarod test.

RESULTS

The BCP exerted a protection in the MES test at the lowest dose of 30 mg kg^-1 at the 4-h interval tested comparable to that of the referent drug phenytoin. The CB2 agonist was ineffective in the scPTZ test. The BCP displayed no neurotoxicity in the rotarod test. The BCP decreased the seizure scores in the KA-induced SE, which effect correlated with a diminished lipid peroxidation. The CB2 agonist exerted a dose-dependent decrease of latency to cross the target area during the three days of testing in the Morris water maze test.

CONCLUSION

Our results suggest that the CB2 receptor agonists might be clinically useful as an adjunct treatment against seizure spread and status epilepticus and concomitant oxidative stress, neurotoxicity and cognitive impairments.

A preliminary study of endocannabinoid system regulation in psychosis: Distinct alterations of CNR1 promoter DNA methylation in patients with schizophrenia

Compelling evidence supports the involvement of the endocannabinoid system (ECS) in psychosis vulnerability. We here evaluated the transcriptional regulation of ECS components in human peripheral blood mononuclear cells (PBMCs) obtained from subjects suffering from bipolar disorder, major depressive disorder and schizophrenia, focusing in particular on the effects of DNA methylation. We observed selective alterations of DNA methylation at the promoter of CNR1, the gene coding for the type-1 cannabinoid receptor, in schizophrenic patients (N=25) with no changes in any other disorder. We confirmed the regulation of CNR1 in a well-validated animal model of schizophrenia, induced by prenatal methylazoxymethanol (MAM) acetate exposure (N=7 per group) where we found, in the prefrontal cortex, a significant increase in CNR1 expression and a consistent reduction in DNA methylation at specific CpG sites of gene promoter. Overall, our findings suggest a selective dysregulation of ECS in psychosis, and highlight the evaluation of CNR1 DNA methylation levels in PBMCs as a potential biomarker for schizophrenia.

Pharmacogenetics and Imaging-Pharmacogenetics of Antidepressant Response: Towards Translational Strategies

Genetic variation underlies both the response to antidepressant treatment and the occurrence of side effects. Over the past two decades, a number of pharmacogenetic variants, among these the SCL6A4, BDNF, FKBP5, GNB3, GRIK4, and ABCB1 genes, have come to the forefront in this regard. However, small effects sizes, mixed results in independent samples, and conflicting meta-analyses results led to inherent difficulties in the field of pharmacogenetics translating these findings into clinical practice. Nearly all antidepressant pharmacogenetic variants have potentially pleiotropic effects in which they are associated with major depressive disorder, intermediate phenotypes involved in emotional processes, and brain areas affected by antidepressant treatment. The purpose of this article is to provide a comprehensive review of the advances made in the field of pharmacogenetics of antidepressant efficacy and side effects, imaging findings of antidepressant response, and the latest results in the expanding field of imaging-pharmacogenetics studies. We suggest there is mounting evidence that genetic factors exert their impact on treatment response by influencing brain structural and functional changes during antidepressant treatment, and combining neuroimaging and genetic methods may be a more powerful way to detect biological mechanisms of response than either method alone. The most promising imaging-pharmacogenetics findings exist for the SCL6A4 gene, with converging associations with antidepressant response, frontolimbic predictors of affective symptoms, and normalization of frontolimbic activity following antidepressant treatment. More research is required before imaging-pharmacogenetics informed personalized medicine can be applied to antidepressant treatment; nevertheless, inroads have been made towards assessing genetic and neuroanatomical liability and potential clinical application.

Lifelong imbalanced LA/ALA intake impairs emotional and cognitive behavior via changes in brain endocannabinoid system

Imbalanced dietary n-3 and n-6 PUFA content has been associated with a number of neurological conditions. Endocannabinoids are n-6 PUFA derivatives, whose brain concentrations are sensitive to modifications of fatty acid composition of the diet and play a central role in the regulation of mood and cognition. As such, the endocannabinoid system appears to be an ideal candidate for mediating the effects of dietary fatty acids on mood and cognition. Lifelong administration of isocaloric α-linolenic acid (ALA)-deficient and -enriched diets induced short-term memory deficits, whereas only dietary ALA enrichment altered emotional reactivity in adult male rats compared with animals fed a standard diet that was balanced in ALA/linoleic acid (LA) ratio. In the prefrontal cortex, both diets reduced 2-AG levels and increased MAG lipase expression, whereas only the enriched diet reduced AEA levels, simultaneously increasing FAAH expression. In the hippocampus, an ALA-enriched diet decreased AEA content and NAPE-PLD expression, and reduced 2-AG content while increasing MAG lipase expression. These findings highlight the importance of a diet balanced in fatty acid content for normal brain functions and to support a link between dietary ALA, the brain endocannabinoid system, and behavior, which indicates that dietary ALA intake is a sufficient condition for altering the endocannabinoid system in brain regions modulating mood and cognition.

Acceptability, Safety, and Efficacy of Oral Administration of Extracts of Black or Red Maca (Lepidium meyenii) in Adult Human Subjects: A Randomized, Double-Blind, Placebo-Controlled Study

The plant maca, grown at 4000 m altitude in the Peruvian Central Andes, contains hypocotyls that have been used as food and in traditional medicine for centuries. The aim of this research was to provide results on some health effects of oral administration of spray-dried extracts of black or red maca (Lepidium meyenii) in adult human subjects living at low (LA) and high altitude (HA). A total of 175 participants were given 3 g of either placebo, black, or red maca extract daily for 12 weeks. Primary outcomes were changes in sexual desire, mood, energy, health-related quality of life score (HRQL), and chronic mountain sickness (CMS) score, or in glycaemia, blood pressure, and hemoglobin levels. Secondary outcomes were acceptability and safety, assessed using the Likert test and side effect self-recording, respectively, and the effect of altitude. At low altitude, 32, 30, and 32 participants started the study receiving placebo, red maca, or black maca, respectively. At high altitudes, 33, 35, and 31 participants started the study receiving placebo, red maca, and black maca, respectively. Consumption of spray-dried extracts of red and black maca resulted in improvement in mood, energy, and health status, and reduced CMS score. Fatty acids and macamides were higher in spray-dried extracts of black maca than in red maca. GABA predominated in spray-dried extracts of red maca. Effects on mood, energy, and CMS score were better with red maca. Black maca and, in smaller proportions, red maca reduced hemoglobin levels only in highlanders with abnormally high hemoglobin levels; neither variety of maca reduced hemoglobin levels in lowlanders. Black maca reduced blood glucose levels. Both varieties produced similar responses in mood, and HRQL score. Maca extracts consumed at LA or HA had good acceptability and did not show serious adverse effects. In conclusion, maca extract consumption relative to the placebo improved quality of life parameters. Differences in the level of improvement between red and black maca are probably due to differences in the composition of these two plant varieties. Both maca extracts were well tolerated and safe.

The involvement of medial septum 5-HT1 and 5-HT2 receptors on ACPA-induced memory consolidation deficit: possible role of TRPC3, TRPC6 and TRPV2

The present study evaluates the roles of serotonergic receptors of the medial septum on amnesia induced by arachidonylcyclopropylamide (ACPA; as selective cannabinoid CB1 receptor agonist) in adult male Wistar rats. Cannulae were implanted in the medial septum of the brain of the rats. The animals were trained in a passive avoidance learning apparatus, and were tested 24 hours after training for step-through latency. Results indicated that post-training medial septum administration of CP94253 (5-HT1B/1D receptor agonist) and cinancerine (as 5-HT2 receptor antagonist) reduced the step-through latency showing an amnesic response, while GR127935 (5-HT1B/1D receptor antagonist) and αm5htm (as 5-HT2A/2B/2D receptor agonist) did not alter memory consolidation by themselves. On continuing the test, the results showed that CP94253 increased and GR127935 did not alter ACPA (0.02 µg/rat)-induced memory impairment, respectively. Other data indicated that αm5htm induced a modulatory effect, while cinancerine restored ACPA-induced amnesia. Using SKF-96365 (inhibitor of transient receptor potential TRPC3/6 and TRPV2 channels) demonstrated that TRPC3, TRPC3 and TRPV2 channels have a significant role, according to our results.

Sex-specific alterations in hippocampal cannabinoid 1 receptor expression following adolescent delta-9-tetrahydrocannabinol treatment in the rat

Marijuana use by adolescents has been on the rise since the early 1990s. With recent legalization and decriminalization acts passed, cannabinoid exposure in adolescents will undoubtedly increase. Human studies are limited in their ability to examine underlying changes in brain biochemistry making rodent models valuable. Studies in adult and adolescent animals show region and sex specific downregulation of the cannabinoid 1 (CB1) receptor following chronic cannabinoid treatment. However, although sex-dependent changes in behavior have been observed during the drug abstinence period following adolescent cannabinoid exposure, little is known about CB1 receptor expression during this critical time. In order to characterize CB1 receptor expression following chronic adolescent Δ-9-tetrahydrocannabinol (THC) exposure, we used [(3)H] CP55,940 binding to assess CB1 receptor expression in the dentate gyrus and areas CA1, CA2, and CA3 of the hippocampus in both male and female adolescent rats at both 24h and 2 weeks post chronic THC treatment. Consistent with other reported findings, we found downregulation of the CB1 receptor in the hippocampal formation at 24h post treatment. While this downregulation persisted in both sexes following two weeks of abstinence in the CA2 region, in females, this downregulation also persisted in areas CA1 and CA3. Expression in the dentate gyrus returned to the normal range by two weeks. These data suggest that selective regions of the hippocampus show persistent reductions in CB1 receptor expression and that these reductions are more widespread in female compared to male adolescents.

Comprehensive Review of Medicinal Marijuana, Cannabinoids, and Therapeutic Implications in Medicine and Headache: What a Long Strange Trip It's Been …

BACKGROUND

The use of cannabis, or marijuana, for medicinal purposes is deeply rooted though history, dating back to ancient times. It once held a prominent position in the history of medicine, recommended by many eminent physicians for numerous diseases, particularly headache and migraine. Through the decades, this plant has taken a fascinating journey from a legal and frequently prescribed status to illegal, driven by political and social factors rather than by science. However, with an abundance of growing support for its multitude of medicinal uses, the misguided stigma of cannabis is fading, and there has been a dramatic push for legalizing medicinal cannabis and research. Almost half of the United States has now legalized medicinal cannabis, several states have legalized recreational use, and others have legalized cannabidiol-only use, which is one of many therapeutic cannabinoids extracted from cannabis. Physicians need to be educated on the history, pharmacology, clinical indications, and proper clinical use of cannabis, as patients will inevitably inquire about it for many diseases, including chronic pain and headache disorders for which there is some intriguing supportive evidence.

OBJECTIVE

To review the history of medicinal cannabis use, discuss the pharmacology and physiology of the endocannabinoid system and cannabis-derived cannabinoids, perform a comprehensive literature review of the clinical uses of medicinal cannabis and cannabinoids with a focus on migraine and other headache disorders, and outline general clinical practice guidelines.

CONCLUSION

The literature suggests that the medicinal use of cannabis may have a therapeutic role for a multitude of diseases, particularly chronic pain disorders including headache. Supporting literature suggests a role for medicinal cannabis and cannabinoids in several types of headache disorders including migraine and cluster headache, although it is primarily limited to case based, anecdotal, or laboratory-based scientific research. Cannabis contains an extensive number of pharmacological and biochemical compounds, of which only a minority are understood, so many potential therapeutic uses likely remain undiscovered. Cannabinoids appear to modulate and interact at many pathways inherent to migraine, triptan mechanisms ofaction, and opiate pathways, suggesting potential synergistic or similar benefits. Modulation of the endocannabinoid system through agonism or antagonism of its receptors, targeting its metabolic pathways, or combining cannabinoids with other analgesics for synergistic effects, may provide the foundation for many new classes of medications. Despite the limited evidence and research suggesting a role for cannabis and cannabinoids in some headache disorders, randomized clinical trials are lacking and necessary for confirmation and further evaluation.

Cannabis and psychopathology: The meandering journey of the last decade

Since its inception cannabis has been observed to be associated with various psycho-pathology. In this paper, the authors have reviewed the advancement made in this area over the last decade. The association between cannabis and schizophrenia has been researched more intensively. The controversy regarding the reliability, clinical utility, and the existence of a cannabis withdrawal syndrome has also been settled. Recent studies also buttressed the possibility of acute and chronic effect of cannabis on various cognitive functions. There has been a plethora of research regarding the treatment for cannabis use disorders. But the new and most interesting area of research is concentrated on the endocannabinoid system and its contribution in various psychiatric disorders.

The endocannabinoid/endovanilloid system and depression

Depression is one of the most frequent causes of disability in the 21st century. Despite the many preclinical and clinical studies that have addressed this brain disorder, the pathophysiology of depression is not well understood and the available antidepressant drugs are therapeutically inadequate in many patients. In recent years, the potential role of lipid-derived molecules, particularly endocannabinoids (eCBs) and endovanilloids, has been highlighted in the pathogenesis of depression and in the action of antidepressants. There are many indications that the eCB/endovanilloid system is involved in the pathogenesis of depression, including the localization of receptors, modulation of monoaminergic transmission, inhibition of the stress axis and promotion of neuroplasticity in the brain. Preclinical pharmacological and genetic studies of eCBs in depression also suggest that facilitating the eCB system exerts antidepressant-like behavioral responses in rodents. In this article, we review the current knowledge of the role of the eCB/endovanilloid system in depression, as well as the effects of its ligands, models of depression and antidepressant drugs in preclinical and clinical settings.

Blockade of 2-arachidonoylglycerol hydrolysis produces antidepressant-like effects and enhances adult hippocampal neurogenesis and synaptic plasticity

The endocannabinoid ligand 2-arachidonoylglycerol (2-AG) is inactivated primarily by monoacylglycerol lipase (MAGL). We have shown recently that chronic treatments with MAGL inhibitor JZL184 produce antidepressant- and anxiolytic-like effects in a chronic unpredictable stress (CUS) model of depression in mice. However, the underlying mechanisms remain poorly understood. Adult hippocampal neurogenesis has been implicated in animal models of anxiety and depression and behavioral effects of antidepressants. We tested whether CUS and chronic JZL184 treatments affected adult neurogenesis and synaptic plasticity in the dentate gyrus (DG) of mouse hippocampus. We report that CUS induced depressive-like behaviors and decreased the number of bromodeoxyuridine-labeled neural progenitor cells and doublecortin-positive immature neurons in the DG, while chronic JZL184 treatments prevented these behavioral and cellular deficits. We also investigated the effects of CUS and chronic JZL184 on a form long-term potentiation (LTP) in the DG known to be neurogenesis-dependent. CUS impaired LTP induction, whereas chronic JZL184 treatments restored LTP in CUS-exposed mice. These results suggest that enhanced adult neurogenesis and long-term synaptic plasticity in the DG of the hippocampus might contribute to antidepressant- and anxiolytic-like behavioral effects of JZL184.

Ethanol self-administration and nicotine treatment increase brain levels of CYP2D in African green monkeys

BACKGROUND AND PURPOSE

CYP2D6 metabolizes many centrally acting drugs, neurotoxins and endogenous neurochemicals, and differences in brain levels of CYP2D have been associated with brain function and drug response. Alcohol consumers and smokers have higher levels of CYP2D6 in brain, but not liver, suggesting ethanol and/or nicotine may induce human brain CYP2D6. We investigated the independent and combined effects of chronic ethanol self-administration and nicotine treatment on CYP2D expression in African green monkeys.

EXPERIMENTAL APPROACH

Forty monkeys were randomized into control, ethanol-only, nicotine-only and ethanol + nicotine groups. Two groups voluntarily self-administered 10% ethanol in sucrose solution for 4 h·day(-1) , whereas two groups consumed sucrose solution on the same schedule. Two groups received daily s.c. injections of 0.5 mg·kg(-1) nicotine in saline bid, whereas two groups were injected with saline on the same schedule.

KEY RESULTS

Both nicotine and ethanol dose-dependently increased CYP2D in brain; brain mRNA was unaffected, and neither drug altered hepatic CYP2D protein or mRNA. The combination of ethanol and nicotine increased brain CYP2D protein levels to a greater extent than either drug alone (1.2-2.2-fold, P < 0.05 among the eight brain regions assessed). Immunohistochemistry revealed the induction of brain CYP2D protein within specific cell types and regions in the treatment groups.

CONCLUSIONS AND IMPLICATIONS

Ethanol and nicotine increase brain CYP2D protein levels in monkeys, in a region and treatment-specific manner, suggesting that CNS drug responses, neurodegeneration and personality may be affected among people who consume alcohol and/or nicotine.

Chronic exposure to WIN55,212-2 affects more potently spatial learning and memory in adolescents than in adult rats via a negative action on dorsal hippocampal neurogenesis

Several epidemiological studies show an increase in cannabis use among adolescents, especially in Morocco for being one of the major producers in the world. The neurobiological consequences of chronic cannabis use are still poorly understood. In addition, brain plasticity linked to ontogeny portrays adolescence as a period of vulnerability to the deleterious effects of drugs. The aim of this study was to investigate the behavioral neurogenic effects of chronic exposure to the cannabinoid agonist WIN55,212-2 during adolescence, by evaluating the emotional and cognitive performances, and the consequences on neurogenesis along the dorso-ventral axis of the hippocampus in adult rats. WIN55,212 was administered intraperitoneally (i.p.) once daily for 20 days to adolescent (27-30 PND) and adult Wistar rats (54-57 PND) at the dose of 1mg/kg. Following a 20 day washout period, emotional and cognitive functions were assessed by the Morris water maze test and the two-way active avoidance test. Twelve hours after, brains were removed and hippocampal neurogenesis was assessed using the doublecortin (DCX) as a marker for cell proliferation. Our results showed that chronic WIN55,212-2 treatment significantly increased thigmotaxis early in the training process whatever the age of treatment, induced spatial learning and memory deficits in adolescent but not adult rats in the Morris water maze test, while it had no significant effect in the active avoidance test during multitrial training in the shuttle box. In addition, the cognitive deficits assessed in adolescent rats were positively correlated to a decrease in the number of newly generated neurons in dorsal hippocampus. These data suggest that long term exposure to cannabinoids may affect more potently spatial learning and memory in adolescent compared to adult rats via a negative action on hippocampal plasticity.

Stress, serotonin, and hippocampal neurogenesis in relation to depression and antidepressant effects

Chronic stressful life events are risk factors for developing major depression, the pathophysiology of which is strongly linked to impairments in serotonin (5-HT) neurotransmission. Exposure to chronic unpredictable stress (CUS) has been found to induce depressive-like behaviours, including passive behavioural coping and anhedonia in animal models, along with many other affective, cognitive, and behavioural symptoms. The heterogeneity of these symptoms represents the plurality of corticolimbic structures involved in mood regulation that are adversely affected in the disorder. Chronic stress has also been shown to negatively regulate adult hippocampal neurogenesis, a phenomenon that is involved in antidepressant effects and regulates subsequent stress responses. Although there exists an enormous body of data on stress-induced alterations of 5-HT activity, there has not been extensive exploration of 5-HT adaptations occurring presynaptically or at the level of the raphe nuclei after exposure to CUS. Similarly, although hippocampal neurogenesis is known to be negatively regulated by stress and positively regulated by antidepressant treatment, the role of neurogenesis in mediating affective behaviour in the context of stress remains an active area of investigation. The goal of this review is to link the serotonergic and neurogenic hypotheses of depression and antidepressant effects in the context of stress. Specifically, chronic stress significantly attenuates 5-HT neurotransmission and 5-HT1A autoreceptor sensitivity, and this effect could represent an endophenotypic hallmark for mood disorders. In addition, by decreasing neurogenesis, CUS decreases hippocampal inhibition of the hypothalamic-pituitary-adrenal (HPA) axis, exacerbating stress axis overactivity. Similarly, we discuss the possibility that adult hippocampal neurogenesis mediates antidepressant effects via the ventral (in rodents; anterior in humans) hippocampus' influence on the HPA axis, and mechanisms by which antidepressants may reverse chronic stress-induced 5-HT and neurogenic changes. Although data are as yet equivocal, antidepressant modulation of 5-HT neurotransmission may well serve as one of the factors that could drive neurogenesis-dependent antidepressant effects through these stress regulation-related mechanisms.

Translational evidence for the involvement of the endocannabinoid system in stress-related psychiatric illnesses

Accumulating evidence over the past decade has highlighted an important role of the endocannabinoid (eCB) system in the regulation of stress and emotional behavior across divergent species, from rodents to humans. The general findings from this work indicate that the eCB system plays an important role in gating and buffering the stress response, dampening anxiety and regulating mood. Work in rodents has allowed researchers to determine the neural mechanisms mediating this relationship while work in human populations has demonstrated the possible importance of this system in stress-related psychiatric diseases, such as post-traumatic stress disorder, generalized anxiety and major depression. These stress-protective effects of eCB signaling appear to be primarily mediated by their actions within corticolimbic structures, particularly the amygdala and the prefrontal cortex. The aim of this review is to provide an up-to-date discussion of the current level of knowledge in this field, as well as address the current gaps in knowledge and specific areas of research that require attention.

Novel insights into depression and antidepressants: a synergy between synaptogenesis and neurogenesis?

Major depressive disorder has been associated with manifold pathophysiological changes. These include metabolic abnormalities in discreet brain areas; modifications in the level of stress hormones, neurotransmitters, and neurotrophic factors; impaired spinogenesis and synaptogenesis in crucial brain areas, such as the prefrontal cortex and the hippocampus; and impaired neurogenesis in the hippocampus. Antidepressant therapy facilitates remission by reversing most of these disturbances, indicating that these dysfunctions may participate causally in depressive symptomatology. However, few attempts have been made to integrate these different pathophysiologies into one model. The present chapter endeavors (1) to review the extant literature in the field, with particular focus on the role of neurogenesis and synaptogenesis in depression; (2) and to suggest a possible interplay between these two processes, as well as, describe the ways by which improving both neurogenesis and synaptogenesis may enable effective recovery by acting on a larger neuronal network.

Cannabinoid receptor genotype moderation of the effects of childhood physical abuse on anhedonia and depression

CONTEXT

The endocannabinoid system has been implicated in stress adaptation and the regulation of mood in rodent studies, but few human association studies have examined these links and replications are limited.

OBJECTIVES

To examine whether a synonymous polymorphism, rs1049353, in exon 4 of the gene encoding the human endocannabinoid receptor (CNR1) moderates the effect of self-reported childhood physical abuse on lifetime anhedonia and depression and to replicate this interaction in an independent sample.

DESIGN, SETTING, AND PARTICIPANTS

Genetic association study in 1041 young US women with replication in an independent Australian sample of 1428 heroin-dependent individuals as cases and 506 participants as neighborhood controls.

MAIN OUTCOME MEASURES

Self-reported anhedonia and depression (with anhedonia).

RESULTS

In both samples, individuals who experienced childhood physical abuse were considerably more likely to report lifetime anhedonia. However, in those with 1 or more copies of the minor allele of rs1049353, this pathogenic effect of childhood physical abuse was attenuated. Thus, in participants reporting childhood physical abuse, although 57.1% of those homozygous for the major allele reported anhedonia, only 28.6% of those who were carriers of the minor allele reported it (P=.01). The rs1049353 polymorphism also buffered the effects of childhood physical abuse on major depressive disorder; however, this influence was largely attributable to anhedonic depression. These effects were also noted in an independent sample, in which minor allele carriers were at decreased risk for anhedonia even when exposed to physical abuse.

CONCLUSIONS

Consistent with preclinical findings, a synonymous CNR1 polymorphism, rs1049353, is linked to the effects of stress attributable to childhood physical abuse on anhedonia and anhedonic depression. This polymorphism reportedly resides in the neighborhood of an exon splice enhancer; hence, future studies should carefully examine its effect on expression and conformational variation in CNR1, particularly in relation to stress adaptation.

Effect of delta-9-tetrahydrocannabinol on behavioral despair and on pre- and postsynaptic serotonergic transmission

Preclinical and clinical studies suggest that direct and indirect cannabinoid agonists, including enhancers of endocannabinoids, engender stress-relieving, anxiolytic and antidepressant effects, mediated by central CB(1) receptors (CB(1)Rs). The effect of the main pharmacologically active principle in cannabis, (-)-trans-Δ(9)-tetrahydrocannabinol (delta-9-THC), on depressive behavior and on the serotonin (5-HT) system, which is implicated in the mechanism of action of antidepressants, has not been extensively clarified. Here, we showed that repeated (5 days), but not single (acute) intraperitoneal (ip) treatment with delta-9-THC (1mg/kg) exerts antidepressant-like properties in the rat forced swim test (FST). This effect was CB(1)R-dependent because it was blocked by the CB(1)R antagonist rimonabant (1mg/kg, ip). Using in vivo electrophysiology, we demonstrated that delta-9-THC modulated dorsal raphe (DR) 5-HT neuronal activity through a CB(1)R-dependent mechanism. Acute intravenous delta-9-THC administration (0.1-1.5mg/kg) elicited a complex response profile, producing excitatory, inhibitory and inert responses of 5-HT neurons. Only excitatory responses were blocked by rimonabant. Finally, repeated but not single delta-9-THC administration (1mg/kg, ip) enhanced tonic 5-HT(1A) receptor activity in the hippocampus, a postsynaptic event commonly elicited by standard antidepressants. These results suggest that delta-9-THC, like other CB(1)R agonists and endocannabinoid enhancers, may possess antidepressant properties at low doses, and could modulate 5-HT transmission in the DR and hippocampus as standard antidepressants such as selective serotonin reuptake inhibitors.

Effects induced by cannabinoids on monoaminergic systems in the brain and their implications for psychiatric disorders

The endocannabinoid system and CB(1) receptors participate in the control of emotional behavior and mood through a functional coupling with the classic monoaminergic systems. In general, the acute stimulation of CB(1) receptors increases the activity (spontaneous firing rate) of noradrenergic (NE), serotonergic (5-HT) and dopaminergic (DA) neurons as well as the synthesis and/or release of the corresponding neurotransmitter in specific brain regions. Notably, the antagonist/inverse agonist rimonabant (SR141617A) can decrease the basal activity of NE and 5-HT neurons, suggesting a tonic/constitutive regulation of these neuronal systems by endocannabinoids acting at CB(1) receptors. Monoaminergic systems are modulated via CB(1) receptors by direct or indirect effects depending on the localization of this inhibitory receptor, which can be present on monoaminergic neurons themselves and/or inhibitory (GABAergic) and/or excitatory (glutamatergic) regulatory neurons. The repeated stimulation of CB(1) receptors is not associated with the induction of tolerance (receptor desensitization) on the activity of NE, 5-HT and DA neurons, in contrast to chronic agonist effects on neurotransmitter synthesis and/or release in some brain regions. CB(1) receptor desensitization may alter the direct and/or indirect effects of cannabinoid drugs modulating the functionality of monoaminergic systems. The sustained activation of monoaminergic neurons by cannabinoid drugs can also be related to changes in the function of presynaptic inhibitory α(2)-adrenoceptors or 5-HT(1A) receptors (autoreceptors and heteroreceptors), whose sensitivity is downregulated or upregulated upon chronic CB(1) agonist exposure. The functional interactions between endocannabinoids and monoaminergic systems in the brain indicate a potential role for CB(1) receptor signaling in the neurobiology of various psychiatric disorders, including major depression and schizophrenia as the major syndromes.

Short-term effects of melatonin and pinealectomy on serotonergic neuronal activity across the light-dark cycle

Melatonin (MLT) and serotonin (5-HT) are two biosynthetically related compounds implicated in several common physiological functions and the etiology of mood disorders. How they interact, though, is not yet fully understood. In this study, single-unit extracellular recordings were used to monitor dorsal raphe nucleus (DR) 5-HT neuronal activity in anesthetized rats, under basal conditions (CTRL), in response to MLT administration, and after pinealectomy (PX) across the light-dark cycle. Under basal conditions, the number of spontaneously active 5-HT neurons and their firing rate were both significantly lower in the dark phase. In the light phase, administration of MLT at low doses (0.5-1 mg/kg, i.v.) decreased 5-HT firing activity. This inhibitory effect of MLT was completely blocked by the MT₁/MT₂ receptor antagonist luzindole, but not by the selective MT(2) receptor antagonist 4P-PDOT, the selective 5-HT(1A) receptor antagonist WAY100635, or by the α₂ adrenoceptor antagonist idazoxan. In the opposite experiment, PX increased 5-HT firing activity in the dark phase, and this was reversed by MLT administration (1 mg/kg, i.v.). Finally, in a forced swim test, MLT (1 mg/kg, i.p.) increased immobility time and decreased swimming behavior. Together, these results suggest that nocturnal MLT secretion imposes tonic inhibitory control over a sub-population of DR 5-HT neurons. This MLT-induced decrease in 5-HT neurotransmission may represent a biological mechanism underlying mood disorders characterized by increased MLT secretion, such as seasonal affective 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.

Endocannabinoid system and psychiatry: in search of a neurobiological basis for detrimental and potential therapeutic effects

Public concern on mental health has noticeably increased given the high prevalence of neuropsychiatric disorders. Cognition and emotionality are the most affected functions in neuropsychiatric disorders, i.e., anxiety disorders, depression, and schizophrenia. In this review, most relevant literature on the role of the endocannabinoid (eCB) system in neuropsychiatric disorders will be presented. Evidence from clinical and animal studies is provided for the participation of CB1 and CB2 receptors (CB1R and CB2R) in the above mentioned neuropsychiatric disorders. CBRs are crucial in some of the emotional and cognitive impairments reported, although more research is required to understand the specific role of the eCB system in neuropsychiatric disorders. Cannabidiol (CBD), the main non-psychotropic component of the Cannabis sativa plant, has shown therapeutic potential in several neuropsychiatric disorders. Although further studies are needed, recent studies indicate that CBD therapeutic effects may partially depend on facilitation of eCB-mediated neurotransmission. Last but not least, this review includes recent findings on the role of the eCB system in eating disorders. A deregulation of the eCB system has been proposed to be in the bases of several neuropsychiatric disorders, including eating disorders. Cannabis consumption has been related to the appearance of psychotic symptoms and schizophrenia. In contrast, the pharmacological manipulation of this eCB system has been proposed as a potential strategy for the treatment of anxiety disorders, depression, and anorexia nervosa. In conclusion, the eCB system plays a critical role in psychiatry; however, detrimental consequences of manipulating this endogenous system cannot be underestimated over the potential and promising perspectives of its therapeutic manipulation.

Endocannabinoids and stress

Endogenous cannabinoids play an important role in the physiology and behavioral expression of stress responses. Activation of the hypothalamic-pituitary-adrenal (HPA) axis, including the release of glucocorticoids, is the fundamental hormonal response to stress. Endocannabinoid (eCB) signaling serves to maintain HPA-axis homeostasis, by buffering basal activity as well as by mediating glucocorticoid fast feedback mechanisms. Following chronic stressor exposure, eCBs are also involved in physiological and behavioral habituation processes. Behavioral consequences of stress include fear and stress-induced anxiety as well as memory formation in the context of stress, involving contextual fear conditioning and inhibitory avoidance learning. Chronic stress can also lead to depression-like symptoms. Prominent in these behavioral stress responses is the interaction between eCBs and the HPA-axis. Future directions may differentiate among eCB signaling within various brain structures/neuronal subpopulations as well as between the distinct roles of the endogenous cannabinoid ligands. Investigation into the role of the eCB system in allostatic states and recovery processes may give insight into possible therapeutic manipulations of the system in treating chronic stress-related conditions in humans.

Depression-resistant endophenotype in mice overexpressing cannabinoid CB(2) receptors

BACKGROUND AND PURPOSE

The present study evaluated the role of CB(2) receptors in the regulation of depressive-like behaviours. Transgenic mice overexpressing the CB(2) receptor (CB2xP) were challenged with different types of acute and chronic experimental paradigms to evaluate their response in terms of depressive-like behaviours.

EXPERIMENTAL APPROACH

Tail suspension test (TST), novelty-suppressed feeding test (NSFT) and unpredictable chronic mild stress tests (CMS) were carried out in CB2xP mice. Furthermore, acute and chronic antidepressant-like effects of the CB(2) receptor-antagonist AM630 were evaluated by means of the forced swimming test (FST) and CMS, respectively, in wild-type (WT) and CB2xP mice. CB(2) gene expression, brain-derived neurotrophic factor (BDNF) gene and protein expressions were studied in mice exposed to CMS by real-time PCR and immunohistochemistry, respectively.

KEY RESULTS

Overexpression of CB(2) receptors resulted in decreased depressive-like behaviours in the TST and NSFT. CMS failed to alter the TST and sucrose consumption in CB2xP mice. In addition, no changes in BDNF gene and protein expression were observed in stressed CB2xP mice. Interestingly, acute administration of AM630 (1 and 3 mg x kg(-1), i.p.) exerted antidepressant-like effects on the FST in WT, but not in CB2xP mice. Chronic administration of AM630 for 4 weeks (1 mg x kg(-1); twice daily, i.p.) blocked the effects of CMS on TST, sucrose intake, CB(2) receptor gene, BDNF gene and protein expression in WT mice.

CONCLUSION AND IMPLICATIONS

Taken together, these results suggest that increased CB(2) receptor expression significantly reduced depressive-related behaviours and that the CB(2) receptor could be a new potential therapeutic target for depressive-related disorders.

The psychiatric side-effects of rimonabant

OBJECTIVE

Experimental evidence has suggested that drugs that enhance cannabinoid type-1 (CB1) receptor activity may induce anxiolytic and antidepressant effects, whilst the opposite has been reported with antagonists. Thus, the objective of the present review is to discuss the potential psychiatric side-effects of CB1 receptor antagonists, such as rimonabant, which has been recently marketed in several countries for the treatment of smoking cessation, obesity and associated metabolic disorders.

METHOD

Literature searches were performed in PubMed and SciELO databases up to February 2009. The terms searched were 'obesity', 'rimonabant', 'cannabinoids', 'unwanted effects', 'diabetes', 'smoking cessation' and 'side-effects'.

RESULTS

Clinical trials have revealed that rimonabant may promote weight loss in obese patients, although it may also induce symptoms of anxiety and depression.

DISCUSSION

Patients taking CB1 receptor antagonists should be carefully investigated for psychiatric side-effects. These drugs should not be prescribed for those already suffering from mental disorders. Nevertheless, the development of new compounds targeting the endocannabinoid system for the treatment of several conditions would be necessary and opportune.

An anatomical and temporal portrait of physiological substrates for fatty acid amide hydrolase

Fatty acid amide hydrolase (FAAH) regulates amidated lipid transmitters, including the endocannabinoid anandamide and its N-acyl ethanolamine (NAE) congeners and transient receptor potential channel agonists N-acyl taurines (NATs). Using both the FAAH inhibitor PF-3845 and FAAH(-/-) mice, we present a global analysis of changes in NAE and NAT metabolism caused by FAAH disruption in central and peripheral tissues. Elevations in anandamide (and other NAEs) were tissue dependent, with the most dramatic changes occurring in brain, testis, and liver of PF-3845-treated or FAAH(-/-) mice. Polyunsaturated NATs accumulated to very high amounts in the liver, kidney, and plasma of these animals. The NAT profile in brain tissue was markedly different and punctuated by significant increases in long-chain NATs found exclusively in FAAH(-/-), but not in PF-3845-treated animals. Suspecting that this difference might reflect a slow pathway for NAT biosynthesis, we treated mice chronically with PF-3845 for 6 days and observed robust elevations in brain NATs. These studies, taken together, define the anatomical and temporal features of FAAH-mediated NAE and NAT metabolism, which are complemented and probably influenced by kinetically distinguishable biosynthetic pathways that produce these lipids in vivo.

Genetic deletion of fatty acid amide hydrolase alters emotional behavior and serotonergic transmission in the dorsal raphe, prefrontal cortex, and hippocampus

Pharmacological blockade of the anandamide-degrading enzyme, fatty acid amide hydrolase (FAAH), produces CB(1) receptor (CB(1)R)-mediated analgesic, anxiolytic-like and antidepressant-like effects in murids. Using behavioral and electrophysiological approaches, we have characterized the emotional phenotype and serotonergic (5-HT) activity of mice lacking the FAAH gene in comparison to their wild type counterparts, and their response to a challenge of the CB(1)R antagonist, rimonabant. FAAH null-mutant (FAAH(-/-)) mice exhibited reduced immobility in the forced swim and tail suspension tests, predictive of antidepressant activity, which was attenuated by rimonabant. FAAH(-/-) mice showed an increase in the duration of open arm visits in the elevated plus maze, and a decrease in thigmotaxis and an increase in exploratory rearing displayed in the open field, indicating anxiolytic-like effects that were reversed by rimonabant. Rimonabant also prolonged the initiation of feeding in the novelty-suppressed feeding test. Electrophysiological recordings revealed a marked 34.68% increase in dorsal raphe 5-HT neural firing that was reversed by rimonabant in a subset of neurons exhibiting high firing rates (33.15% mean decrease). The response of the prefrontocortical pyramidal cells to the 5-HT(2A/2C) agonist (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane ((+/-)-DOI) revealed desensitized 5-HT(2A/2C) receptors, likely linked to the observed anxiolytic-like behaviors. The hippocampal pyramidal response to the 5-HT(1A) antagonist, WAY-100635, indicates enhanced tonus on the hippocampal 5-HT(1A) heteroreceptors, a hallmark of antidepressant-like action. Together, these results suggest that FAAH genetic deletion enhances anxiolytic-like and antidepressant-like effects, paralleled by altered 5-HT transmission and postsynaptic 5-HT(1A) and 5-HT(2A/2C) receptor function.

The Potential Role of Cannabinoids in Modulating Serotonergic Signaling by Their Influence on Tryptophan Metabolism

Phytocannabinoids present in Cannabis plants are well known to exert potent anti-inflammatory and immunomodulatory effects. Previously, we have demonstrated that the psychoactive D9-tetrahydrocannabinol (THC) and the non-psychotropic cannabidiol (CBD) modulate mitogen-induced Th1-type immune responses in peripheral blood mononuclear cells (PBMC). The suppressive effect of both cannabinoids on mitogen-induced tryptophan degradation mediated by indoleamine-2,3-dioxygenase (IDO), suggests an additional mechanism by which antidepressive effects of cannabinoids might be linked to the serotonergic system. Here, we will review the role of tryptophan metabolism in the course of cell mediated immune responses and the relevance of cannabinoids in serotonergic signaling. We conclude that in particular the non-psychotropic CBD might be useful for the treatment of mood disorders in patients with inflammatory diseases, since this cannabinoid seems to be safe and its effects on activation-induced tryptophan degradation by CBD were more potent as compared to THC.

Synthesis and evaluation of paracetamol esters as novel fatty acid amide hydrolase inhibitors

Fatty acid amide hydrolase (FAAH) is the key hydrolytic enzyme for the endogenous cannabinoid receptor ligand anandamide. The synthesis and evaluation for their FAAH inhibitory activities of a series of 18 paracetamol esters are described. Structure-activity relationship studies indicated that the ester (33) with a 2-(4-(2-(trifluoromethyl)pyridin-4-ylamino)phenyl)acetic acid substituent was the most potent analogue in this series. The compound inhibited FAAH activity in a competitive manner with a K(i) value of 0.16 microM. The compound was also able to inhibit the FAAH activity in rat basophilic leukemia cells as assessed by measuring either the hydrolysis of anandamide, the FAAH-dependent cellular accumulation of anandamide, or the FAAH-dependent recycling of tritium to the cell membranes. The compound also inhibited the activity of monoacylglycerol lipase (MGL), the enzyme responsible for the hydrolysis of the endogenous cannabinoid receptor ligand 2-arachidonoylglycerol, with an IC(50) value of 1.9 microM. It is concluded that the compound may be a useful template for the design of potent novel inhibitors of FAAH.