Endocannabinoid lipids and mediated system: implications for alcoholism and neuropsychiatric disorders

The Synaptic Interactions of Alcohol and the Endogenous Cannabinoid System

PURPOSE

A growing body of evidence has implicated the endocannabinoid (eCB) system in the acute, chronic, and withdrawal effects of alcohol/ethanol on synaptic function. These eCB-mediated synaptic effects may contribute to the development of alcohol use disorder (AUD). Alcohol exposure causes neurobiological alterations similar to those elicited by chronic cannabinoid (CB) exposure. Like alcohol, cannabinoids alter many central processes, such as cognition, locomotion, synaptic transmission, and neurotransmitter release. There is a strong need to elucidate the effects of ethanol on the eCB system in different brain regions to understand the role of eCB signaling in AUD.

SEARCH METHODS

For the scope of this review, preclinical studies were identified through queries of the PubMed database.

SEARCH RESULTS

This search yielded 459 articles. Clinical studies and papers irrelevant to the topic of this review were excluded.

DISCUSSION AND CONCLUSIONS

The endocannabinoid system includes, but is not limited to, cannabinoid receptors 1 (CB₁), among the most abundantly expressed neuronal receptors in the brain; cannabinoid receptors 2 (CB₂); and endogenously formed CB₁ ligands, including arachidonoylethanolamide (AEA; anandamide), and 2-arachidonoylglycerol (2-AG). The development of specific CB₁ agonists, such as WIN 55,212-2 (WIN), and antagonists, such as SR 141716A (rimonabant), provide powerful pharmacological tools for eCB research. Alcohol exposure has brain region-specific effects on the eCB system, including altering the synthesis of endocannabinoids (e.g., AEA, 2-AG), the synthesis of their precursors, and the density and coupling efficacy of CB₁. These alcohol-induced alterations of the eCB system have subsequent effects on synaptic function including neuronal excitability and postsynaptic conductance. This review will provide a comprehensive evaluation of the current literature on the synaptic interactions of alcohol exposure and eCB signaling systems, with an emphasis on molecular and physiological synaptic effects of alcohol on the eCB system. A limited volume of studies has focused on the underlying interactions of alcohol and the eCB system at the synaptic level in the brain. Thus, the data on synaptic interactions are sparse, and future research addressing these interactions is much needed.

Spatio-temporal effects of acute alcohol intoxication on endocannabinoid system in rat brain and blood

The endocannabinoid system (ECS) has been shown to play a critical role in the regulation of alcohol intake and alcohol-related behaviors. However, there are discrepancies between studies examining the interaction of the ECS and alcohol administration due to different experimental procedures. The present study aims at clarifying the time course effects of acute alcohol consumption on the ECS in the peripheral circulatory systems and central nervous systems of the same cohort of subjects. We have closely monitored the critical indicators reflecting changes of the ECS during the entire process from alcohol absorption to its metabolization, after acute alcohol (4.5 g/kg) intake by intragastric administration, including two key endocannabinoids (arachidonoylethanolamide and 2-arachidonoylglycerol) and their hydrolytic enzymes (fatty acid amide hydrolase and monoacylglycerol lipase) in blood and three brain regions, as well as a crucial and abundant receptor (cannabinoid 1 receptor) of the ECS in the three brain regions. Our results indicate that acute alcohol consumption inhibits endocannabinoid (eCB) production in the blood and in the prefrontal cortex of the brain, whereas the reverse was observed in the brain regions of the hippocampus and striatum. The variation between levels of two hydrolytic enzymes in the blood and in the three brain regions failed to reach statistical significance. After acute alcohol consumption, CB1R levels in striatum, hippocampus, and prefrontal cortex showed a similar trend of increasing, while the significant changes occurred at different time points. The present findings reveal different ligand-receptor changing patterns in the blood and in different brain regions, supporting the notion that the ECS plays a vital role in acute alcohol intoxication. Additionally, the temporal effects of alcohol on key elements of the ECS of blood and different brain nuclei were different. Our investigation may lead to a deeper understanding of the effect of acute alcohol consumption on the ECS.

Bipolar disorder and the endocannabinoid system

OBJECTIVE

Bipolar disorder (BD) is a debilitating, lifelong neuropsychiatric illness characterised by unsteady mood states which vacillate from (hypo)mania to depression. Despite the availability of pharmaceutical agents which can be effective in ameliorating the acute affective symptoms and prevent episodic relapse, BD is inadequately treated in a subset of patients. The endocannabinoid system (ECS) is known to exert neuromodulatory effects on other neurotransmitter systems critical in governing emotions. Several studies ranging from clinical to molecular, as well as anecdotal evidence, have placed a spotlight on the potential role of the ECS in the pathophysiology of BD. In this perspective, we present advantages and disadvantages of cannabis use in the management of illness course of BD and provide mechanistic insights into how this system might contribute to the pathophysiology of BD.

RESULTS

We highlight the putative role of selective cannabinoid receptor 2 (CB2) agonists in BD and briefly discuss findings which provide a rationale for targeting the ECS to assuage the symptoms of BD. Further, data encourage basic and clinical studies to determine how cannabis and cannabinoids (CBs) can affect mood and to investigate emerging CB-based options as probable treatment approaches.

CONCLUSION

The probable role of the ECS has been almost neglected in BD; however, from data available which suggest a role of ECS in mood control, it is justified to support conducting comprehensive studies to determine whether ECS manipulation could positively affect BD. Based on the limited available data, we suggest that activation of CB2 may stabilise mood in this disorder.

Drinking during pregnancy: Potential role of endocannabinoid signaling in fetal alcohol effects

Alcohol is a well-recognized teratogen that can cause variable physical and behavioral effects on the fetus. Alcohol use and abuse during pregnancy is one of the major health and societal problems and has been linked to a wide range of birth defects in the offspring collectively termed as fetal alcohol spectrum disorder (FASD). The severity of abnormalities may depend on a number of factors that include the amount, the frequency, the period during gestation and the route of alcohol administration. The current knowledge about the neurobiological basis of FASD is limited. However, recent studies have suggested that the membrane-derived lipids especially bioactive endogenous cannabinoids (eCB) such as arachidonyl ethanolamide and 2-arachidonyl glycerol resulting from alcohol exposure, may play a significant role in modulating neurophysiological and neurobehavioral effects in chronic alcohol exposed adult animals. Based on these findings and on reported studies on the role of eCB signaling in neurodevelopment and behavior, it is speculated that the eCB signaling may play a critical role in fetal alcohol syndrome and FASD-related behavioral effects. The current discussion will touch upon some of the mechanistic explanations about the role of eCB signaling system in FASD and provide further guidance for future direction.

Current Heavy Alcohol Consumption is Associated with Greater Cognitive Impairment in Older Adults

BACKGROUND

The acute consumption of excessive quantities of alcohol causes well-recognized neurophysiological and cognitive alterations. As people reach advanced age, they are more prone to cognitive decline. To date, the interaction of current heavy alcohol (ethanol [EtOH]) consumption and aging remains unclear. This study tested the hypothesis that negative consequences of current heavy alcohol consumption on neurocognitive function are worse with advanced age. Further, we evaluated the relations between lifetime history of alcohol dependence and neurocognitive function METHODS: Sixty-six participants underwent a comprehensive neurocognitive battery. Current heavy EtOH drinkers were classified using National Institute on Alcohol Abuse and Alcoholism criteria (EtOH heavy, n = 21) based on the Timeline follow-back and a structured clinical interview and compared to nondrinkers, and moderate drinkers (EtOH low, n = 45). Of the total population, 53.3% had a lifetime history of alcohol dependence. Neurocognitive data were grouped and analyzed relative to global and domain scores assessing: global cognitive function, attention/executive function, learning, memory, motor function, verbal function, and speed of processing.

RESULTS

Heavy current EtOH consumption in older adults was associated with poorer global cognitive function, learning, memory, and motor function (ps < 0.05). Furthermore, lifetime history of alcohol dependence was associated with poorer function in the same neurocognitive domains, in addition to the attention/executive domain, irrespective of age (ps < 0.05).

CONCLUSIONS

These data suggest that while heavy current alcohol consumption is associated with significant impairment in a number of neurocognitive domains, history of alcohol dependence, even in the absence of heavy current alcohol use, is associated with lasting negative consequences for neurocognitive function.

Acute and chronic ethanol exposure differentially regulate CB1 receptor function at glutamatergic synapses in the rat basolateral amygdala

The endogenous cannabinoid (eCB) system has been suggested to play a key role in ethanol preference and intake, the acute effects of ethanol, and in the development of withdrawal symptoms following ethanol dependence. Ethanol-dependent alterations in glutamatergic signaling within the lateral/basolateral nucleus of the amygdala (BLA) are critical for the development and expression of withdrawal-induced anxiety. Notably, the eCB system significantly regulates both glutamatergic and GABAergic synaptic activity within the BLA. Chronic ethanol exposure significantly alters eCB system expression within regions critical to the expression of emotionality and anxiety-related behavior, including the BLA. Here, we investigated specific interactions between the BLA eCB system and its functional regulation of synaptic activity during acute and chronic ethanol exposure. In tissue from ethanol naïve-rats, a prolonged acute ethanol exposure caused a dose dependent inhibition of glutamatergic synaptic activity via a presynaptic mechanism that was occluded by CB1 antagonist/inverse agonists SR141716a and AM251. Importantly, this acute ethanol inhibition was attenuated following 10 day chronic intermittent ethanol vapor exposure (CIE). CIE exposure also significantly down-regulated CB1-mediated presynaptic inhibition at glutamatergic afferent terminals but spared CB1-inhibition of GABAergic synapses arising from local inhibitory-interneurons. CIE also significantly elevated BLA N-arachidonoylethanolamine (AEA or anandamide) levels and decreased CB1 receptor protein levels. Collectively, these data suggest a dynamic regulation of the BLA eCB system by acute and chronic ethanol.

Neurochemical and neurostructural plasticity in alcoholism

The behavioral manifestations of alcoholism are primarily attributable to the numerous and lasting adaptations that occur in the brain as a result of chronic heavy alcohol consumption. As will be reviewed here, these adaptations include alcohol-induced plasticity in chemical neurotransmission, density and morphology of dendritic spines, as well as neurodegeneration and cerebral atrophy. Within the context of these neuroadaptations that have been observed in both human and animal studies, we will discuss how these changes potentially contribute to the cognitive and behavioral dysfunctions that are hallmark features of alcoholism, as well as how they reveal novel potential pharmacological targets for the treatment of this disorder.

Endocannabinoid system: A newer molecular target for the treatment of alcohol-related behaviors

The cannabinoid (CB) receptors, endocannabinoids (eCB) and their synthesizing and catabolizing enzymes and the proteins involved in their transport, constitute what is now recognized as the eCB system. The eCBs are a class of lipids that have been identified as retrograde messengers and produce their effects via presynaptic CB receptors. The major function of the eCBs has been suggested to be that of modulating the release of several neurotransmitters implicated in a number of biological functions that include reward and reinforcement. There is now significant evidence to suggest that the eCB system plays an important role in the development of alcohol tolerance, dependence and relapse. Recent studies suggest that the pharmacological manipulation of the eCB system has the potential not only to block the direct reinforcing properties of alcohol but also alleviate behavioral abnormalities associated with relapse. There is also accumulating evidence that points to the possible utility of the eCB system targeted drugs in the treatment of alcoholism-related behavioral disorders. The agents that block CB1 receptor function or inhibit the synthesis of eCBs are attractive candidate drugs that need to be explored. Further understanding of the role of the eCB system in molecular mechanism/s that underlies alcoholism-related behaviors should lead to a better treatment of this devastating disorder.

CNS effects of CB2 cannabinoid receptors: beyond neuro-immuno-cannabinoid activity

There are two well characterized cannabinoid receptors (CBRs), CB1-Rs and CB2-Rs, with other candidates, such as GPR55, PPARs and vanilloid TRPV1 (VR1) receptors, which are either activated by cannabinoids and/or endocannabinoids (eCBs). The neuronal and functional expression of CB2-Rs in the brain has been much less well characterized in comparison with the expression of the ubiquitous CB1-Rs. CB2-Rs were previously thought to be predominantly expressed in immune cells in the periphery and were traditionally referred to as peripheral CB2-Rs. We and others have now demonstrated the expression of CB2-Rs in neuronal, glial and endothelial cells in the brain, and this warrants a re-evaluation of the CNS effects of CB2-Rs. In the present review we summarize our current understanding of CNR2 genomic structure, its polymorphic nature, subtype specificity, from mice to human subjects, and its variants that confer vulnerabilities to neuropsychiatric disorders beyond neuro-immuno-cannabinoid activity.

Commentary: Functional Neuronal CB2 Cannabinoid Receptors in the CNS

Cannabinoids are the constituents of the marijuana plant (Cannabis sativa). There are numerous cannabinoids and other natural compounds that have been reported in the cannabis plant. The recent progress in marijuana-cannabinoid research include the discovery of an endocannabinoid system with specific genes coding for cannabinoid receptors (CBRs) that are activated by smoking marijuana, and that the human body and brain makes its own marijuana-like substances called endocannabinoids that also activate CBRs. This new knowledge and progress about cannabinoids and endocannabinoids indicate that a balanced level of endocannabinoids is important for pregnancy and that the breast milk in animals and humans has endocannabinoids for the growth and development of the new born. There are two well characterized cannabinoid receptors termed CB1-Rs and CB2-Rs and these CBRs are perhaps the most abundant G-protein coupled receptors that are expressed at high levels in many regions of the mammalian brain. The expression of CB1-Rs in the brain and periphery and the identification of CB2-Rs in immune cells and during inflammation has been extensively studied and characterized. However, the expression of functional neuronal CB2-Rs in the CNS has been much less well established and characterized in comparison to the expression of abundant brain CB1-Rs and functional neuronal CB2-Rs has ignited debate and controversy. While the issue of the specificity of CB2-R antibodies remains, many recent studies have reported the discovery and functional characterization of functional neuronal CB2-Rs in the CNS beyond neuro-immuno cannabinoid activity.

Endogenous cannabinoids in post-mortem brains of Cloninger type 1 and 2 alcoholics

The endogenous cannabinoid (EC) system has been recently implicated in several neuropsychiatric disorders. This study analyzed post-mortem brain regions of Cloninger type 1 (n=9) and 2 (n=8) alcoholics and non-alcoholic controls (n=10) for ECs by quantitative liquid chromatography with triple quadrupole mass spectrometric detection. A significant difference was found in anandamide (AEA) levels in nucleus accumbens (NAcc) between the three groups (p=0.047). AEA levels were significantly lower when compared to controls in both perigenual anterior cingulate (p=0.017) and frontal cortices (p=0.018) of type 1 alcoholics. Similar trends were observed for dihomo-gamma-linolenoyl ethanolamide and docosahexaenoyl ethanolamide, but not for 2-arachidonoylglycerol, palmitoyl ethanolamide, or oleoyl ethanolamide. Although preliminary, and from diagnostic groups with a relatively small number of subjects and substantially different mean ages for each group, these results suggest that the EC system may be hyperactive in type 2 alcoholics and hypoactive in type 1 alcoholics.

Development and validation of a quantitative method for the determination of 12 endocannabinoids and related compounds in human plasma using liquid chromatography-tandem mass spectrometry

A sensitive and specific LC-MS/MS method for the quantification of the endocannabinoids and related structures anandamide, 2-arachidonoyl glycerol, 2-arachidonyl glycerol ether, O-arachidonoyl ethanolamide, dihomo-gamma-linolenoyl ethanolamide, docosatetraenoyl ethanolamide, N-arachidonoyl dopamine, N-arachidonyl glycine, N-oleoyl dopamine, oleoyl ethanolamide, palmitoyl ethanolamide, and stearoyl ethanolamide in human plasma was developed and validated. Compounds were extracted using acetonitrile followed by solid-phase extraction. Separation was performed on a Xterra C8 column using gradient elution coupled to a triple-quadrupole MS. LLOQ levels ranged from 0.02 to 1.75 microg/mL, LODs ranged from 0.0002 to 0.1266 ng/mL, and accuracies were >80% (except stearoyl ethanolamide at lowest spike level) at all spike levels.

Cannabinoid CB1 receptor antagonists attenuate cocaine's rewarding effects: experiments with self-administration and brain-stimulation reward in rats

Previous studies suggest that cannabinoid CB1 receptors do not appear to be involved in cocaine's rewarding effects, as assessed by the use of SR141716A, a prototypic CB1 receptor antagonist and CB1-knockout mice. In the present study, we found that blockade of CB1 receptors by AM 251 (1-10 mg/kg), a novel CB1 receptor antagonist, dose-dependently lowered (by 30-70%) the break point for cocaine self-administration under a progressive-ratio (PR) reinforcement schedule in rats. The same doses of SR141716 (freebase form) maximally lowered the break point by 35%, which did not reach statistical significance. Neither AM 251 nor SR141716 altered cocaine self-administration under a fixed-ratio (FR2) reinforcement schedule. AM 251 (0.1-3 mg/kg) also significantly and dose-dependently inhibited (by 25-90%) cocaine-enhanced brain stimulation reward (BSR), while SR141716 attenuated cocaine's BSR-enhancing effect only at 3 mg/kg (by 40%). When the dose was increased to 10 or 20 mg/kg, both AM 251 and SR141716 became less effective, with AM 251 only partially inhibiting cocaine-enhanced BSR and PR cocaine self-administration, and SR141716 having no effect. AM 251 alone, at all doses tested, had no effect on BSR, while high doses of SR141716 alone significantly inhibited BSR. These data suggest that blockade of CB1 receptors by relatively low doses of AM 251 dose-dependently inhibits cocaine's rewarding effects, whereas SR141716 is largely ineffective, as assessed by both PR cocaine self-administration and BSR. Thus, AM 251 or other more potent CB1 receptor antagonists deserve further study as potentially effective anti-cocaine medications.

Targeted modulators of the endogenous cannabinoid system: future medications to treat addiction disorders and obesity

The endogenous endocannabinoid system encompasses a family of natural signaling lipids ("endocannabinoids") functionally related to (9)-tetrahydrocannabinol, the psychoactive ingredient of marijuana (cannabis), along with proteins that modulate the endocannabinoids, including enzymes, transporters, and receptors. The endocannabinoid system's ubiquitous regulatory actions in health and disease underscore its importance to mammalian (patho)physiology and suggest discrete targets through which it may be modulated for therapeutic gain. Medications based on the endocannabinoid system are an important focus of contemporary translational research, particularly with respect to substance abuse and obesity, two prevalent disorders with a pathogenic component of endocannabinoid system hyperactivity. Pressing health care needs have made the rational design of targeted CB1 cannabinoid-receptor modulators a promising route to future medications with significant therapeutic impact against psychobehavioral and metabolic disturbances having a reward-supported appetitive component.

The fatty acid amide hydrolase C385A (P129T) missense variant in cannabis users: studies of drug use and dependence in Caucasians

A genetic variation in fatty acid amide hydrolase (FAAH), C385A (P129T), has been previously associated with risk for problem street drug use. FAAH is a mammalian enzyme that inactivates neuromodulatory-signaling lipids including the endogenous cannabinoid 1 receptor agonist anandamide. We investigated in adult Caucasians (N = 749) whether this FAAH variant altered the risk for trying, regular use of or dependence on cannabis, alcohol or nicotine, traditional "gateway" drugs. Consistent with our knowledge that the A/A genotype results in reduced FAAH expression and activity in humans, subjects with the A/A genotype were less likely to be THC dependent than subjects with either a C/C or C/A genotype (11% vs. 26%, P < 0.05). No association was observed between the A/A genotype and risk for alcohol or tobacco regular use, or DSM IV dependence. Controlling for regular use of nicotine and sedatives, both identified as confounders, those with the A/A genotype were at significantly reduced risk for being THC dependent (OR 0.25, 95% CI: 0.07-0.88) as compared with those with the C/A or C/C genotype, supporting a link between alterations in the endocannabinoid system and THC dependence. Unexpectedly, we found an increased risk for regular use of sedatives among the A/A genotype group. The relationship between the FAAH A/A genotype and risk for drug dependence in this study was drug class specific, suggesting it is not part of a more general drug abuse effect. These results, particularly the observation of altered risk for sedative drug use, should be investigated further in multiple ethnic populations.

Bidirectional alterations of hippocampal cannabinoid 1 receptors and their endogenous ligands in a rat model of alcohol withdrawal and dependence

BACKGROUND

The hippocampus is strongly implicated in memory processes and contains high concentrations of both cannabinoid receptors and their endogenous ligands. Chronic alcohol consumption impairs a variety of cognitive and performance tasks, including memory and learning. As the activation of cannabinoid receptors by their endogenous ligands modulates hippocampal neurotransmission, we hypothesized that the impaired memory and learning in alcoholism may be due to alterations in the hippocampal endocannabinoid system.

METHODS

We used the rat chronic intermittent ethanol (CIE) model for alcohol withdrawal and dependence which involves intermittent episodes of ethanol intoxication (60 doses) and withdrawal (approximating binge drinking episodes in humans). We measured the levels of cannabinoid 1 receptor (CB1R) protein (Western blot using a C-terminal-directed antibody), CB1R mRNA (real-time RT-PCR), CB1R localization (immunocytochemistry), tissue levels of the endocannabinoids N-arachidonoylethanolamine/anandamide (AEA) and 2-arachidonoylglycerol (2-AG), and function (patch-clamp recordings of depolarization-induced suppression of inhibition (DSI), as well as effects of CB1R agonist WIN 55,212-2 on inhibitory currents) in the hippocampus of CIE rats and their saline-treated controls.

RESULTS

Results were obtained in saline and CIE-treated rats after 2 and 40 days of withdrawal (DW) from their respective treatments. In 2 DW CIE rats, CB1R mRNA and protein levels were decreased by 27% (p<0.05) compared with saline controls. Surprisingly, in 40 DW CIE rats, CB1R mRNA increased by 100% and protein increased by 21%, confirmed by immunohistochemistry. Hippocampal [2-AG] increased in both 2 and 40 DW CIE rats; [AEA] increased only at 40 DW. Hippocampal DSI of CIE rats was significantly reduced at 2 DW but not at 40 DW. The CB1R agonist WIN 55,212-2 (0.5 microM) produced a significantly greater decrease in the frequency of spontaneous inhibitory currents from saline-treated rats compared with CIE rats at 2 DW, but not at 40 DW.

CONCLUSIONS

These data demonstrate that CIE treatment and withdrawal transiently down-regulates hippocampal CB1 Rs followed by a long-term up-regulation, including increased levels of endogenous cannabinoids. These findings are consistent with our hypothesis and suggest that long-term up-regulation of hippocampal CB1Rs may contribute to the long-term cognitive impairments in alcoholism. The data further suggest that the effectiveness of CB1R blockade in decreasing alcohol consumption may be greater after protracted abstinence from alcohol.

The endocannabinoid system as an emerging target of pharmacotherapy

The recent identification of cannabinoid receptors and their endogenous lipid ligands has triggered an exponential growth of studies exploring the endocannabinoid system and its regulatory functions in health and disease. Such studies have been greatly facilitated by the introduction of selective cannabinoid receptor antagonists and inhibitors of endocannabinoid metabolism and transport, as well as mice deficient in cannabinoid receptors or the endocannabinoid-degrading enzyme fatty acid amidohydrolase. In the past decade, the endocannabinoid system has been implicated in a growing number of physiological functions, both in the central and peripheral nervous systems and in peripheral organs. More importantly, modulating the activity of the endocannabinoid system turned out to hold therapeutic promise in a wide range of disparate diseases and pathological conditions, ranging from mood and anxiety disorders, movement disorders such as Parkinson's and Huntington's disease, neuropathic pain, multiple sclerosis and spinal cord injury, to cancer, atherosclerosis, myocardial infarction, stroke, hypertension, glaucoma, obesity/metabolic syndrome, and osteoporosis, to name just a few. An impediment to the development of cannabinoid medications has been the socially unacceptable psychoactive properties of plant-derived or synthetic agonists, mediated by CB(1) receptors. However, this problem does not arise when the therapeutic aim is achieved by treatment with a CB(1) receptor antagonist, such as in obesity, and may also be absent when the action of endocannabinoids is enhanced indirectly through blocking their metabolism or transport. The use of selective CB(2) receptor agonists, which lack psychoactive properties, could represent another promising avenue for certain conditions. The abuse potential of plant-derived cannabinoids may also be limited through the use of preparations with controlled composition and the careful selection of dose and route of administration. The growing number of preclinical studies and clinical trials with compounds that modulate the endocannabinoid system will probably result in novel therapeutic approaches in a number of diseases for which current treatments do not fully address the patients' need. Here, we provide a comprehensive overview on the current state of knowledge of the endocannabinoid system as a target of pharmacotherapy.

Role of the endocannabinoid system in depression and suicide

Depression is one of the most prevalent forms of neuropsychiatric disorder and is a major cause of suicide worldwide. The prefrontal cortex is a crucial brain region that is thought to be involved in the regulation of mood, aggression and/or impulsivity and decision making, which are altered in suicidality. Evidence of the role of the endocannabinoid (EC) system in the neurobiology of neuropsychiatric disorders is beginning to emerge. The behavioral effects of ECs are believed to be mediated through the central cannabinoid CB1 receptor. Alterations in the levels of ECs, and in the density and coupling efficacy of CB1 receptors, have been reported in the prefrontal cortex of depressed and alcoholic suicide victims. These findings support our hypothesis that altered EC function contributes to the pathophysiological aspects of suicidal behavior. Here, we provide a brief overview of the role of the EC system in alcoholism, depression and suicide, and discuss possible therapeutic interventions and directions for future research.

Tardive dyskinesia and essential fatty acids

Tardive dyskinesia (TD) is a movement disorder described in individuals who have been treated with anti-dopaminergic agents. The pathophysiology of this condition remains to be fully elucidated. Several mechanisms like dopaminergic supersensitivity, dysfunction of striatonigral, GABAergic neurons and disturbed balance between dopaminergic and cholinergic systems have been described. Essential fatty acids (EFAs) are important components of neuronal membrane and the EFA content of these membranes can significantly influence neuronal functioning. Lower levels of EFAs have been reported in red blood cells (RBC) and plasma of individuals with moderate to severe TD. Supplementation with EFAs (omega-3 and omega-6 and ethyl-EPA) have been tried to alleviate TD in open and double-blind clinical trials and in some animal models of TD. In addition, antioxidants (Vitamin E) and melatonin have been tried. However, smaller numbers of patients and shortened length of clinical studies make it difficult to draw any definitive conclusions. Large multi-centre studies with sound methodology of both EFAs and antioxidants are needed.