THE ENDOCANNABINOID SYSTEM: PHYSIOLOGY AND PHARMACOLOGY

[Endocannabinoid system and bowel inflammation]

The endocannabinoid system is an important regulatory system of multiple functions of the body in all vertebrates. There are 2 specific receptors, CB1 and CB2, through which the cannabinoids exert their effect. CB1-receptors mainly express themselves in myenteric plexuses and submucosal epithelium of the gastrointestinal tract, suggesting their implication in the inhibition of the peristalsis and gastrointestinal contraction. CB2-receptors are expressed in the tissue and immune cells, such as T and B-lymphocytes, monocytes and polymorphonuclear neutrophils, exerting an immunomodulator effect. The role of the endocannabinoid system is not completely known, but there is enough evidence that confirms an important role in the decrease of inflammation through the reduction of the release of pro-inflammatory cytokines. Therefore, it may exert a protective role in many of the points where the homeostasis breaks in inflammatory bowel disease. Research about the mechanisms and effects of the endocannabinoid system in the gastrointestinal tract will allow advancing in the therapy of this illness.

Enhancement of endocannabinoid neurotransmission through CB1 cannabinoid receptors counteracts the reinforcing and psychostimulant effects of cocaine

Cannabinoids, in contrast to typical drugs of abuse, have been shown to exert complex effects on behavioural reinforcement and psychomotor function. We have shown that cannabinoid agonists lack reinforcing/rewarding properties in the intracranial self-stimulation (ICSS) paradigm and that the CB1 receptor (CB1R) agonist WIN55,212-2 attenuates the reward-facilitating actions of cocaine. We sought to determine the effects of the endocannabinoid neurotransmission enhancer AM-404 (1, 3, 10, 30 mg/kg) on the changes in ICSS threshold and locomotion elicited by cocaine and extend the study of the effects of WIN55,212-2 (0.3, 1, 3 mg/kg) on cocaine-induced hyperlocomotion. AM-404 did not exhibit reward-facilitating properties, and actually increased self-stimulation threshold at the highest dose. Cocaine significantly reduced self-stimulation threshold, without altering maximal rates of responding. AM-404 (10 mg/kg) attenuated this action of cocaine, an effect which was reversed by pretreatment with the selective CB1R antagonist SR141716A. WIN55,212-2 decreased locomotion at the two highest doses, an effect that was blocked by SR141716A; AM-404 had no effect on locomotion. Cocaine caused a significant, dose-dependent increase in locomotion, which was reduced by WIN55,212-2 and AM-404. SR141716A blocked the effects of WIN55,212-2 and AM-404 on cocaine-induced hyperlocomotion. SR141716A alone had no effect on ICSS threshold or locomotion. These results indicate that cannabinoids may interfere with brain reward systems responsible for the expression of acute reinforcing/rewarding properties of cocaine, and provide further evidence that the cannabinoid system could be explored as a potential drug discovery target for the treatment of psychostimulant addiction and pathological states associated with psychomotor overexcitability.

Novel aspects of adipocyte-induced skeletal muscle insulin resistance

Insulin resistance in skeletal muscle is an early event in the development of diabetes with obesity being one of the major contributing factors. Conditioned medium (CM) from differentiated human adipocytes impairs insulin signalling in human skeletal muscle cells. Recent data on adipocyte-induced insulin resistance in skeletal muscle cells describes underlying mechanisms of this process. Skeletal muscle insulin resistance involves multiple pathways and irreversible changes in the expression level of critical proteins. Furthermore, the reversibility of insulin resistance could be demonstrated. Several strategies to combat insulin resistance have been developed. One recent approach to treat obesity and the metabolic syndrome is the use of endocannabinoid receptor antagonists such as rimonabant. These compounds might also reduce insulin resistance in type 2 diabetes with effects on adipose tissue and liver and possibly skeletal muscle.

The incentive salience of alcohol: translating the effects of genetic variant in CNR1

CONTEXT

The gene that codes for cannabinoid receptor 1 (CNR1) represents an important target for investigations designed to elucidate individual differences in the etiology of alcohol dependence.

OBJECTIVE

To achieve a better understanding of the role of the CNR1 gene in the etiology and treatment of alcohol dependence.

DESIGN

The present investigation spans multiple levels of analysis, including receptor binding in postmortem brain tissue, neuroimaging, human laboratory models, and analyses of treatment outcome data.

RESULTS

Findings indicate that the C allele of rs2023239 is associated with greater CB1 binding in the prefrontal cortex, greater alcohol cue-elicited brain activation in the midbrain and prefrontal cortex, greater subjective reward when consuming alcohol, and more positive outcomes after treatment with a medication that targets the mesocorticolimbic neurocircuitry. In addition, there were strong correlations between cue-elicited brain activation and alcohol consumption measures in individuals with the C allele.

CONCLUSION

Individuals with the C allele may be more susceptible to changes in the mesocorticolimbic neurocircuitry that is involved in the attribution of incentive salience after repeated exposure to alcohol.

The role of the CB1 receptor in the regulation of sleep

During the 1990s, transmembranal proteins in the central nervous system (CNS) that recognize the principal compound of marijuana, the delta-9-tetrahydrocannabinol (Delta9-THC) were described. The receptors were classified as central or peripheral, CB1 and CB2, respectively. To this date, it has been documented the presence in the CNS of specific lipids that bind naturally to the CB1/CB2 receptors. The family of endogenous cannabinoids or endocannabinoids comprises oleamide, arachidonoylethanolamine, 2-arachidonylglycerol, virodhamine, noladin ether and N-arachidonyldopamine. Pharmacological experiments have shown that those compounds induce cannabimimetic effects. Endocannabinoids are fatty acid derivates that have a variety of biological actions, most notably via activation of the cannabinoid receptors. The endocannabinoids have an active role modulating diverse neurobiological functions, such as learning and memory, feeding, pain perception and sleep generation. Experimental evidence shows that the administration of Delta9-THC promotes sleep. The activation of the CB1 receptor leads to an induction of sleep, this effect is blocked via the selective antagonist. Since the system of the endogenous cannabinoids is present in several species, including humans, this leads to the speculation of the neurobiological role of the endocannabinoid system on diverse functions such as sleep modulation. This review discusses the evidence of the system of the endocannabinoids as well as their physiological role in diverse behaviours, including the modulation of sleep.

The pharmacology of the endocannabinoid system: functional and structural interactions with other neurotransmitter systems and their repercussions in behavioral addiction

Addiction is a chronic, recurring and complex disorder. It is characterized by anomalous behaviors that are linked to permanent or long-lasting neurobiological alterations. Furthermore, the endocannabinoid system has a crucial role in mediating neurotransmitter release as one of the main neuromodulators of the mammalian central nervous system. The purpose of the present review is to instruct readers about the functional and structural interactions between the endocannabinoid system and the main neurotransmitter systems of the central nervous system in the context of drug addiction. With this aim, we have systematically reviewed the main findings of most of the existing literature that explores cross-talk in the five brain areas that are most traditionally implicated in addiction: amygdala, prefrontal cortex, nucleus accumbens, hippocampus and ventral tegmental area (VTA). The neurotransmission systems influenced by the pharmacology of the endocannabinoid system in these brain areas, which are reviewed here, are gamma-aminobutyric acid (GABA), glutamate, the main biogenic amines (dopamine, noradrenaline and serotonin), acetylcholine and opioids. We show that all of these neurotransmitter systems can be modulated differentially in each brain area by the activation or deactivation of cannabinoid CB1 brain receptors. Specifically, most of the studies relate to the hippocampus and nucleus accumbens. Moreover, the neurotransmitter with the fewest number of related studies is acetylcholine (excepting in the hippocampus), whereas there is a large number that evaluates GABA, glutamate and dopamine. Finally, we propose a possible interpretation of the role of the endocannabinoid system in the phenomenon of addiction.

The endogenous cannabinoid system modulates nicotine reward and dependence

A growing body of evidence suggests that the endogenous cannabinoid system modulates the addictive properties of nicotine, the main component of tobacco that produces rewarding effects. In our study, complementary transgenic and pharmacological approaches were used to test the hypothesis that the endocannabinoid system modulates nicotine reward and dependence. An acute injection of nicotine elicited normal analgesic and hypothermic effects in cannabinoid receptor (CB)(1) knockout (KO) mice and mice treated with the CB(1) antagonist rimonabant. However, disruption of CB(1) receptor signaling blocked nicotine reward, as assessed in the conditioned place preference (CPP) paradigm. In contrast, genetic deletion, or pharmacological inhibition of fatty acid amide hydrolase (FAAH), the enzyme responsible for catabolism of the endocannabinoid anandamide, enhanced the expression of nicotine CPP. Although the expression of spontaneous nicotine withdrawal (14 days, 24 mg/kg/day nicotine) was unaffected in CB(1) KO mice, acute administration of rimonabant (3 mg/kg) ameliorated somatic withdrawal signs in wild-type mice. Increasing endogenous levels of anandamide through genetic or pharmacological approaches exacerbated the physical somatic signs of spontaneous nicotine withdrawal in a milder withdrawal model (7 days, 24 mg/kg/day nicotine). Moreover, FAAH-compromised mice displayed increased conditioned place aversion in a mecamylamine-precipitated model of nicotine withdrawal. These findings indicate that endocannabinoids play a role in the rewarding properties of nicotine as well as nicotine dependence liability. Specifically, increasing endogenous cannabinoid levels magnifies, although disrupting CB(1) receptor signaling, attenuates nicotine reward and withdrawal. Taken together, these results support the hypothesis that cannabinoid receptor antagonists may offer therapeutic advantages to treat tobacco dependence.

Central versus peripheral antagonism of cannabinoid CB1 receptor in obesity: effects of LH-21, a peripherally acting neutral cannabinoid receptor antagonist, in Zucker rats

The endogenous cannabinoid system plays an important modulatory role in feeding behaviour and metabolism, acting at both central and peripheral levels. Chronic administration of cannabinoid CB(1) receptor antagonists has been found to be effective in experimental obesity. However, clinically available cannabinoid receptor antagonists are inverse agonists that can target CB(1) receptors located in both central circuits regulating appetite and motivation and in peripheral organs regulating metabolism and energy expenditure. This profile complicates understanding of cannabinoid CB(1) receptor blockade as a therapeutic strategy in obesity and metabolic disorders. This review aims to explore the relevance of both inverse agonism and peripheral cannabinoid receptor blockade on the beneficial actions of chronic cannabinoid receptor blockade, by comparing the actions of the reference antagonist/inverse agonist rimonabant and the newly designed drug LH-21. LH-21 is a triazol derivative and a neutral cannabinoid receptor antagonist; it has a poor penetration rate into the central nervous system. When given acutely it decreases food intake and enhances the anorectic actions of oleoylethanolamide, a feeding suppressant lipid that acts on peripheral sensory terminals in a similar way as rimonabant. Unlike rimonabant, chronic administration of LH-21 (3 mg/kg) reduces feeding but does not improve hypertriglyceridaemia or hypercholesterolaemia; nor does it reduce liver fat deposits in Zucker rats. These results suggest that the inverse agonism and/or the antagonism of central cannabinoid CB(1) receptors are necessary for the metabolic benefits of cannabinoid CB(1) receptor blockade, but not for the appetite reduction.

Eicosanoids in non-febrile thermoregulation

Eicosanoids are a large group of oxygenated fatty acids [viz., omega-3 (n-3) and omega-6 (n-6) C(20) polyunsaturated fatty acids], the most important source being the omega-6 cell membrane-derived arachidonic acid (AA). Eicosanoids are produced by many different cell types; through their ligation and activation of specific membrane-bound and intracellular receptors, they regulate myriad physiological and pathological functions, including body temperature (T(b)). However, the thermoregulatory role of eicosanoids has mainly been associated with fever, i.e., with T(b) changes induced during illness; their importance in maintaining T(b) during health remains unclear. In this review, we address the question of whether AA-derived mediators (viz., prostaglandins, leukotrienes and other lipoxygenase metabolites, and the endocannabinoids/endovanilloids) are involved in normal (non-febrile) thermoregulation. We conclude that although prostaglandin E(2) is a principal mediator of fever, it is unlikely to be involved in the maintenance of normal T(b). Other eicosanoids reviewed also seem to have no major role in non-febrile thermoregulation. Newly discovered signaling pathways for eicosanoids, such as the endovanilloid system, may participate in thermoregulation, but further studies are required before definitive conclusions can be made.

Cannabinoid receptor 1 gene (CNR1) and susceptibility to a quantitative phenotype for hebephrenic schizophrenia

Functional alterations of components of the endogenous cannabinoid system, in particular of the cannabinoid receptor 1 protein (CB1), are hypothetical contributors to many of the symptoms seen in schizophrenia. Variants within the cannabinoid receptor 1 gene (CNR1) have been shown to be directly associated with the hebephrenic form of schizophrenia in a Japanese population. This finding, however, has yet to be replicated. In the present study we sought to study the same (AAT)n-repeat microsatellite of the CNR1 gene which showed association to hebephrenic schizophrenia in Japan, and to investigate whether this microsatellite showed association to a hebephrenic type of schizophrenia in a family-based association study in a population of the Central Valley of Costa Rica. The Lifetime Dimensions of Psychosis Scale and a best estimate consensus process were utilized to identify subjects with schizophrenia who had an elevated lifetime dimensional score for negative and disorganized symptoms, which we used as a proxy for "hebephrenia." Using the Family Based Association Test we found association of these hebephrenic subjects and the (AAT)n-repeat marker of the CNR1 (multi-allelic P = 0.0368). Our hypothesis that an association with the (AAT)n-repeat marker of CNR1 would not be found with the more general type of schizophrenia was also confirmed. Schizophrenic subjects with prominent lifetime scores for disorganization and negative symptoms (dimension for hebephrenia) are associated with the CNR1 gene and present a type of symptomatology that resembles chronic cannabinoid-induced psychosis. The current finding points to the possibility of different genetic and pathophysiologic mechanisms underlying different types of schizophrenia.

Attention deficit hyperactivity disorder and substance use disorders

Attention deficit hperactivity disorder (ADHD) is highly prevalent among adolescents who have substance use disorder (SUD). Several lines of evidence, although not conclusive, suggest that ADHD might have an independent effect on SUD liability. It is still to be determined, however, whether this association is mediated by conduct disorder. This article reviews ADHD and SUD.

Modulation of the balance between cannabinoid CB(1) and CB(2) receptor activation during cerebral ischemic/reperfusion injury

Cannabinoid receptor activation has been shown to modulate both neurotransmission (CB(1)) and neuroinflammatory (CB(2)) responses. There are conflicting reports in the literature describing the influence of cannabinoid receptor activation on ischemic/reperfusion injury. The goal of this study was to evaluate how changing the balance between CB(1) and CB(2) activation following cerebral ischemia influences outcome. CB(1) and CB(2) expression were tested at different times after transient middle cerebral artery occlusion (MCAO) in mice by real-time RT-PCR. Animals subjected to 1 h MCAO were randomly assigned to receive different treatments: a CB(1) antagonist, a CB(2) antagonist, a CB(2) agonist, a CB(1) antagonist plus CB(2) agonist, a CB(2) antagonist plus CB(2) agonist or an equal volume of vehicle as control. Cerebral blood flow was continuously monitored during ischemia; cerebral infarction and neurological deficit were tested 24 h after MCAO. Cerebral CB(1) and CB(2) mRNA expression undertook dynamic changes during cerebral ischemia. The selective CB(1) antagonist significantly decreased cerebral infarction by 47%; the selective CB(2) antagonist increased infarction by 26% after 1 h MCAO followed by 23 h reperfusion in mice. The most striking changes were obtained by combining a CB(1) antagonist with a CB(2) agonist. This combination elevated the cerebral blood flow during ischemia and reduced infarction by 75%. In conclusion, during cerebral ischemia/reperfusion injury, inhibition of CB(1) receptor activation is protective while inhibition of CB(2) receptor activation is detrimental. The greatest degree of neuroprotection was obtained by combining an inhibitor of CB(1) activation with an exogenous CB(2) agonist.

Delta9-tetrahydrocannabinol (THC) and AM 404 protect against cerebral ischaemia in gerbils through a mechanism involving cannabinoid and opioid receptors

BACKGROUND AND PURPOSE

It has been suggested that the endocannabinoid system elicits neuroprotection against excitotoxic brain damage. In the present study the therapeutic potential of AM 404 on ischaemia-induced neuronal injury was investigated in vivo and compared with that of the classical cannabinoid receptor type 1 (CB1) agonist, delta 9-tetraydrocannabinol (THC), using a model of transient global cerebral ischaemia in the gerbil.

EXPERIMENTAL APPROACH

The effects of AM 404 (0.015-2 mg kg(-1)) and THC (0.05-2 mg kg(-1)), given 5 min after ischaemia, were measured from 1 h to 7 days in terms of electroencephalographic (EEG) total spectral power, spontaneous motor activity, memory function, rectal temperature and hippocampal CA1 neuronal count.

KEY RESULTS

Over the dose range tested, AM 404 (2 mg kg(-1)) and THC (1 mg kg(-1)) completely reversed the ischaemia-induced behavioural, EEG and histological damage. Only THC (1 and 2 mg kg(-1)) induced a decrease of body temperature. Pretreatment with the selective CB1 receptor antagonist, AM 251 (1 mg kg(-1)) and the opioid antagonist, naloxone (2 mg kg(-1)) reversed the protective effect induced by both AM 404 and THC while the TRPV1 vanilloid antagonist, capsazepine (0.01 mg kg(-1)), was ineffective.

CONCLUSIONS AND IMPLICATIONS

Our findings demonstrate that AM 404 and THC reduce neuronal damage caused by bilateral carotid occlusion in gerbils and that this protection is mediated through an interaction with CB1 and opioid receptors. Endocannabinoids might form the basis for the development of new neuroprotective drugs useful for the treatment of stroke and other neurodegenerative pathologies.

A possible role for the endocannabinoid system in the neurobiology of depression

The present review synthetically describes the currently advanced hypotheses for a neurobiological basis of depression, ranging from the classical monoaminergic to the more recent neurotrophic hypothesis. Moreover, the Authors review the available preclinical and clinical evidence suggesting a possible role for the endocannabinoid system in the physiopathology of depression. Indeed, in spite of the reporting of conflicting results, the pharmacological enhancement of endocannabinoid activity at the CB1 cannabinoid receptor level appears to exert an antidepressant-like effect in some animal models of depression. On the contrary, a reduced activity of the endogenous cannabinoid system seems to be associated with the animal model of depression, namely the chronic mild stress model. Moreover, a few studies have reported an interaction of antidepressants with the endocannabinoid system. With regard to clinical studies, several authors have reported an alteration of endocannabinoid serum levels in depression, while post mortem studies have demonstrated increased levels of endocannabinoids associated to a concomitant hyperactivity of CB1 receptor in the prefrontal cortex of suicide victims. No clinical trials carried out using cannabinoids in the treatment of affective disorders have been published to date, although anecdotal reports have described both antidepressant and antimanic properties of cannabis as well as the ability of cannabis to induce mania that has also been documented. These findings are discussed, leading us to conclude that, although data available are sufficient to suggest a possible involvement of the endogenous cannabinoid system in the neurobiology of depression, additional studies should be performed in order to better elucidate the role of this system in the physiopathology of depression.

Single and multiple doses of rimonabant antagonize acute effects of smoked cannabis in male cannabis users

RATIONALE

A single 90-mg dose of the cannabinoid CB1 receptor antagonist rimonabant attenuates effects of smoked cannabis in humans.

OBJECTIVES

The objective of this study is to evaluate whether repeated daily 40-mg doses of rimonabant can attenuate effects of smoked cannabis to the same extent as a single higher (90 mg) dose.

MATERIALS AND METHODS

Forty-two male volunteers received one of three oral drug regimens in a randomized, double blind, parallel group design: (1) 40 mg rimonabant daily for 15 days, (2) placebo for 14 days, then 90 mg rimonabant on day 15, or (3) placebo for 15 days. All participants smoked an active or placebo cannabis cigarette 2 h after medication on days 8 and 15. Subjective effects were measured with visual analog scales and the marijuana-scale of the Addiction Research Center Inventory.

RESULTS

Cannabis-induced tachycardia was significantly lower for the 40-mg group on day 8 and for the 40 and 90 mg rimonabant groups on day 15 as compared to placebo. The 40-mg dose significantly decreased peak subjective effects on day 8. Neither the 90-mg nor 40-mg doses significantly decreased peak subjective effects on day 15. Rimonabant treatment did not significantly affect Delta(9)-tetrahydrocannabinnol pharmacokinetics.

CONCLUSIONS

Repeated lower daily rimonabant doses (40 mg) attenuated the acute physiological effects of smoked cannabis to a similar degree as a single 90-mg dose; repeated 40-mg doses attenuated subjective effects after 8 but not 15 days.

The anandamide transport inhibitor AM404 reduces ethanol self-administration

The endocannabinoid system mediates in the pharmacological actions of ethanol and genetic studies link endocannabinoid signaling to alcoholism. Drugs activating cannabinoid CB1 receptors have been found to promote alcohol consumption but their effects on self-administration of alcohol are less clear because of the interference with motor performance. To avoid this problem, a novel pharmacological approach to the study of the contribution of the cannabinoid system in alcoholism may be to use drugs that locally amplify the effects of alcohol on endogenous cannabinoids. In the present study we addressed this model by studying the effects of the anandamide transport inhibitor N-(4-hydroxyphenyl) arachidonoyl-ethanolamide (AM404) on both ethanol self-administration and reinstatement of alcohol-seeking behavior in rats. The results show that AM404 significantly reduced ethanol self-administration in a dose-dependent manner but failed to modify reinstatement for lever pressing induced by the stimulus associated with alcohol. This effect was not due to a motor depressant effect and was not related to a decrease in general motivational state, as it was not effective in other reward paradigms such as lever pressing for a saccharin solution. The mechanism of action of AM404 does not involve cannabinoid CB1 receptors as the CB1-selective antagonist SR141716A did not block the reduction of ethanol self-administration induced by the anandamide uptake blocker. Moreover, 3-(1,1-dimethylheptyl)-(-)-11-hydroxy-delta 8-tetrahydrocannabinol (HU-210), a classical cannabinoid receptor agonist, did not affect ethanol self-administration. The effects of AM404 are not mediated by either vanilloid VR1 receptors or cannabinoid CB2 receptors because it is not antagonized by either the VR1 receptor antagonist capsazepine or the CB2 antagonist AM630. These results indicate that AM404 may be considered as an innovative approach to reduce alcohol consumption.

Local enhancement of cannabinoid CB1 receptor signalling in the dorsal hippocampus elicits an antidepressant-like effect

Systemic administration of direct cannabinoid CB1 receptor agonists and inhibitors of the hydrolytic enzyme fatty acid amide hydrolase have been shown to elicit antidepressant effects. Moreover, the endocannabinoid system in the hippocampus is sensitive to both chronic stress and antidepressant administration, suggesting a potential role of this system in emotional changes associated with these regimens. The aim of this study was to determine if cannabinoid CB1 receptors in the hippocampus modulate emotionality in rats as assessed via the forced swim test. Male Sprague-Dawley rats were bilaterally implanted with cannulae directed at the dentate gyrus of the dorsal hippocampus and subsequently received three infusions of either the cannabinoid CB1 receptor agonist HU-210 (1 and 2.5 microg), the fatty acid amide hydrolase inhibitor URB597 (0.5 and 1 microg), the cannabinoid CB1 receptor antagonist AM251 (1 and 2.5 microg), or vehicle (dimethyl sulfoxide) and were assessed in the forced swim test. Infusion of both doses of HU-210 resulted in a dramatic reduction in immobility and increase in swimming behaviour, indicative of an antidepressant response, which was partially reversed by coadministration of AM251. No effect of URB597 administration or any effect following the administration of AM251 alone was, however, observed. These data indicate that activation of CB1 receptors in the dentate gyrus of the hippocampus results in an antidepressant-like response. Collectively, these data highlight the potential importance of changes in the hippocampal endocannabinoid system following stress or antidepressant treatment with respect to the manifestation and/or treatment of depression.

COX-2 suppresses tissue factor expression via endocannabinoid-directed PPARdelta activation

Although cyclooxygenase (COX)-2 inhibitors (coxibs) are effective in controlling inflammation, pain, and tumorigenesis, their use is limited by the recent revelation of increased adverse cardiovascular events. The mechanistic basis of this side effect is not well understood. We show that the metabolism of endocannabinoids by the endothelial cell COX-2 coupled to the prostacyclin (PGI₂) synthase (PGIS) activates the nuclear receptor peroxisomal proliferator–activated receptor (PPAR) δ, which negatively regulates the expression of tissue factor (TF), the primary initiator of blood coagulation. Coxibs suppress PPARδ activity and induce TF expression in vascular endothelium and elevate circulating TF activity in vivo. Importantly, PPARδ agonists suppress coxib-induced TF expression and decrease circulating TF activity. We provide evidence that COX-2–dependent attenuation of TF expression is abrogated by coxibs, which may explain the prothrombotic side-effects for this class of drugs. Furthermore, PPARδ agonists may be used therapeutically to suppress coxib-induced cardiovascular side effects.

N-Acylethanolamine metabolism interacts with abscisic acid signaling in Arabidopsis thaliana seedlings

N-Acylethanolamines (NAEs) are bioactive acylamides that are present in a wide range of organisms. In plants, NAEs are generally elevated in desiccated seeds, suggesting that they may play a role in seed physiology. NAE and abscisic acid (ABA) levels were depleted during seed germination, and both metabolites inhibited the growth of Arabidopsis thaliana seedlings within a similar developmental window. Combined application of low levels of ABA and NAE produced a more dramatic reduction in germination and growth than either compound alone. Transcript profiling and gene expression studies in NAE-treated seedlings revealed elevated transcripts for a number of ABA-responsive genes and genes typically enriched in desiccated seeds. The levels of ABI3 transcripts were inversely associated with NAE-modulated growth. Overexpression of the Arabidopsis NAE degrading enzyme fatty acid amide hydrolase resulted in seedlings that were hypersensitive to ABA, whereas the ABA-insensitive mutants, abi1-1, abi2-1, and abi3-1, exhibited reduced sensitivity to NAE. Collectively, our data indicate that an intact ABA signaling pathway is required for NAE action and that NAE may intersect the ABA pathway downstream from ABA. We propose that NAE metabolism interacts with ABA in the negative regulation of seedling development and that normal seedling establishment depends on the reduction of the endogenous levels of both metabolites.

Cannabis use and risk of psychotic or affective mental health outcomes: a systematic review

BACKGROUND

Whether cannabis can cause psychotic or affective symptoms that persist beyond transient intoxication is unclear. We systematically reviewed the evidence pertaining to cannabis use and occurrence of psychotic or affective mental health outcomes.

METHODS

We searched Medline, Embase, CINAHL, PsycINFO, ISI Web of Knowledge, ISI Proceedings, ZETOC, BIOSIS, LILACS, and MEDCARIB from their inception to September, 2006, searched reference lists of studies selected for inclusion, and contacted experts. Studies were included if longitudinal and population based. 35 studies from 4804 references were included. Data extraction and quality assessment were done independently and in duplicate.

FINDINGS

There was an increased risk of any psychotic outcome in individuals who had ever used cannabis (pooled adjusted odds ratio=1.41, 95% CI 1.20-1.65). Findings were consistent with a dose-response effect, with greater risk in people who used cannabis most frequently (2.09, 1.54-2.84). Results of analyses restricted to studies of more clinically relevant psychotic disorders were similar. Depression, suicidal thoughts, and anxiety outcomes were examined separately. Findings for these outcomes were less consistent, and fewer attempts were made to address non-causal explanations, than for psychosis. A substantial confounding effect was present for both psychotic and affective outcomes.

INTERPRETATION

The evidence is consistent with the view that cannabis increases risk of psychotic outcomes independently of confounding and transient intoxication effects, although evidence for affective outcomes is less strong. The uncertainty about whether cannabis causes psychosis is unlikely to be resolved by further longitudinal studies such as those reviewed here. However, we conclude that there is now sufficient evidence to warn young people that using cannabis could increase their risk of developing a psychotic illness later in life.

Cannabinoid CB(2) receptor activation decreases cerebral infarction in a mouse focal ischemia/reperfusion model

Cannabinoid CB(2) Receptor (CB(2)) activation has been shown to have immunomodulatory properties without psychotropic effects. The hypothesis of this study is that selective CB(2) agonist treatment can attenuate cerebral ischemia/reperfusion injury. Selective CB(2) agonists (O-3853, O-1966) were administered intravenously 1 h before transient middle cerebral artery occlusion (MCAO) or 10 mins after reperfusion in male mice. Leukocyte/endothelial interactions were evaluated before MCAO, 1 h after MCAO, and 24 h after MCAO via a closed cranial window. Cerebral infarct volume and motor function were determined 24 h after MCAO. Administration of the selective CB(2) agonists significantly decreased cerebral infarction (30%) and improved motor function (P<0.05) after 1 h MCAO followed by 23 h reperfusion in mice. Transient ischemia in untreated animals was associated with a significant increase in leukocyte rolling and adhesion on both venules and arterioles (P<0.05), whereas the enhanced rolling and adhesion were attenuated by both selective CB(2) agonists administered either at 1 h before or after MCAO (P<0.05). CB(2) activation is associated with a reduction in white blood cell rolling and adhesion along cerebral vascular endothelial cells, a reduction in infarct size, and improved motor function after transient focal ischemia.

Role of endocannabinoids in alcohol consumption and intoxication: studies of mice lacking fatty acid amide hydrolase

Endocannabinoid signaling plays the important role in regulation of ethanol intake. Fatty acid amide hydrolase (FAAH) is a key membrane protein for metabolism of endocannabinoids, including anandamide, and blockade of FAAH increases the level of anandamide in the brain. To determine if FAAH regulates ethanol consumption, we studied mutant mice with deletion of the FAAH gene. Null mutant mice showed higher preference for alcohol and voluntarily consumed more alcohol than wild-type littermates. There was no significant difference in consumption of sweet or bitter solutions. To determine the specificity of FAAH for ethanol intake, we studied additional ethanol-related behaviors. There were no differences between null mutant and wild-type mice in severity of ethanol-induced acute withdrawal, conditioned taste aversion to alcohol, conditioned place preference, or sensitivity to hypnotic effect of ethanol. However, null mutant mice showed shorter duration of loss of righting reflex induced by low doses of ethanol (3.2 and 3.4 g/kg) and faster recovery from motor incoordination induced by ethanol. All three behavioral phenotypes (increased preference for ethanol, decreased sensitivity to ethanol-induced sedation, and faster recovery from ethanol-induced motor incoordination) seen in mutant mice were reproduced in wild-type mice by injection of a specific inhibitor of FAAH activity--URB597. These data suggest that increased endocannabinoid signaling increased ethanol consumption owing to decreased acute ethanol intoxication.

Rimonabant: A novel selective cannabinoid-1 receptor antagonist for treatment of obesity

PURPOSE

The pharmacology, pharmacokinetics, clinical efficacy, safety, drug interactions, and dosage and administration of rimonabant in the treatment of obesity and related metabolic factors are reviewed.

SUMMARY

Discovery of the cannabinoid receptors has led to the development of rimonabant, a cannabinoid-1 (CB(1)) antagonist. Selective blockade of this receptor has been shown to lead to decreased appetite and food intake in animal models. Clinical studies have shown that rimonabant 20 mg once daily produces significant decreases in weight and waist circumference in obese human subjects and improves the lipid profile and glucose control. The frequency of metabolic syndrome also decreased significantly with rimonabant 20 mg daily. Limited data are available regarding the pharmacokinetics and pharmacodynamics of rimonabant. Preclinical data have demonstrated a long duration of action. As of yet, no drug-drug, drug-food, or drug-disease interactions have been identified with rimonabant. Adverse reactions occurred rarely, with nausea, dizziness, diarrhea, arthralgia, and back pain being the most common. Psychiatric disorders, including depression and anxiety, were the most common reasons for subjects to withdraw from rimonabant studies. Rimonabant has been shown to be safe for up to two years of treatment. Further research will clarify currently unknown areas, including pharmacokinetics, drug interactions, and the drug's role in standard therapy.

CONCLUSION

Rimonabant, a selective CB(1) antagonist, is a novel treatment option for obese and overweight individuals. Significant weight loss, decrease in waist circumference, and improvements in lipid profile and glucose control have been shown in clinical trials of rimonabant.

Cannabis and anxiety and depression in young adults: a large prospective study

OBJECTIVE

To examine whether age of first use or frequency of use of cannabis is associated with anxiety and depression (AD) in young adults, independent of known potential confounders, including the use of other illicit drugs.

METHOD

A cohort of 3,239 Australian young adults was followed from birth to the age of 21 when data on AD were obtained from sample members along with information on their use of cannabis at 21 years. Potential confounding factors were prospectively measured when the child was born and at 14 years.

RESULTS

After controlling for confounding factors, those who started using cannabis before age 15 years and used it frequently at 21 years were more likely to report symptoms of AD in early adulthood (odds ratio 3.4; 95% CI 1.9-6.1). This association was of similar magnitude for those who had only used cannabis and those who reported having used cannabis and other illicit drugs.

CONCLUSION

The relationship between early-onset and frequent use of cannabis and symptoms of AD is independent of individual and family backgrounds. Frequent cannabis use is associated with increased AD in young adults independently of whether the person also uses other illicit drugs.

The CB1 cannabinoid receptor antagonist rimonabant chronically prevents the nicotine-induced relapse to alcohol

Preclinical and clinical research shows that the cannabinoid brain receptor type 1 (CB(1)) modulates alcohol- and nicotine-related behaviors. Throughout the nicotine-induced relapse to alcohol, the rats were pre-treated for 10 days with the CB(1) cannabinoid receptor antagonist rimonabant (0, 0.03, 0.3 and 3.0 mg/kg i.p.). In this condition, a long-lasting nicotine-induced relapse to alcohol was observed, and this effect was reversed in a dose-dependent manner with rimonabant. Surprisingly, rats that were not exposed to nicotine developed tolerance to the effects of rimonabant from the sixth day. Also, 3.0 mg/kg of rimonabant reduced the responses for sucrose. Evaluation in the Elevated Plus-Maze after nicotine treatment did not reveal anxiogenic effects. Finally, at the conclusion of rimonabant treatment, a rapid reinstatement of alcohol consumption was detected. These results suggest that rimonabant can prevent the relapse to alcohol, even when an interaction with nicotine exists-the most frequent situation in human alcohol abuse.

Effects of Cannabinoids on Synaptic Transmission in the Frog Neuromuscular Junction

This study aimed to investigate the function of the cannabinoid receptor in the neuromuscular junction of the frog (Rana pipiens). Miniature end-plate potentials were recorded using the intracellular electrode recording technique in the cutaneous pectoris muscle in the presence of the cannabinoid agonists WIN55212-2 (WIN; R-(+)-[2,3-dihydro-5-methyl-3-[(morpholinyl)]-pyrolol[1,2,3de]-1,4-benzoxazinyl]-(1-naphthalenyl)methanone) and arachidonylcyclopropylamide [ACPA; N-(2-cyclopropyl)-5Z,8Z,11Z,147-eicosatetraenamide] and the cannabinoid antagonists 1-(2,4-dichlorophenyl)-5-(4-iodophenyl)-4-methyl-N-4-morpholinyl-1H-pyrazole-3-carboxamide (AM281) and 6-iodo-2-methyl-1-[2-(4-morpholinyl)ethyl]-1H-indol-3-yl](4-methoxyphenyl)methanone (AM630). Adding WIN to the external medium decreased the frequency and amplitude of the miniature end-plate potentials (MEPPs); the WIN EC50 value was 5.8+/-1.0 microM. Application of ACPA, a selective agonist of cannabinoid receptor CB1, also decreased the frequency of the MEPPs; the ACPA EC50 value was 115.5+/-6.5 nM. The CB2 antagonist AM630 did not inhibit the effects of WIN, indicating that its action is not mediated through the CB2 receptor. However, the CB1 antagonist AM281 inhibited the effects of WIN and ACPA, suggesting that their actions are mediated through the CB1 receptor. Pretreatment with the pertussis toxin inhibited the effects of WIN and ACPA, suggesting that their effects are mediated through Gi/o protein activation. The N-type Ca2+ channel blocker omega-conotoxin GVIA (omega-CgTX) diminished the frequency of the MEPPs, with an omega-CgTX EC50 value of 2.5+/-0.40 microM. Blocking the N-type Ca2+ channels with 5 microM omega-CgTX before addition of ACPA to the bath had no additional inhibitory effect on the MEPPs, whereas in the presence of 1 microM omega-CgTX, ACPA had an additional inhibition effect. These results suggest that cannabinoids modulate transmitter release in the end-plate of the frog neuromuscular junction by activating CB1 cannabinoid receptors in the nerve ending.

The acute effects of cannabinoids on memory in humans: a review

RATIONALE

Cannabis is one of the most frequently used substances. Cannabis and its constituent cannabinoids are known to impair several aspects of cognitive function, with the most robust effects on short-term episodic and working memory in humans. A large body of the work in this area occurred in the 1970s before the discovery of cannabinoid receptors. Recent advances in the knowledge of cannabinoid receptors' function have rekindled interest in examining effects of exogenous cannabinoids on memory and in understanding the mechanism of these effects.

OBJECTIVE

The literature about the acute effects of cannabinoids on memory tasks in humans is reviewed. The limitations of the human literature including issues of dose, route of administration, small sample sizes, sample selection, effects of other drug use, tolerance and dependence to cannabinoids, and the timing and sensitivity of psychological tests are discussed. Finally, the human literature is discussed against the backdrop of preclinical findings.

RESULTS

Acute administration of Delta-9-THC transiently impairs immediate and delayed free recall of information presented after, but not before, drug administration in a dose- and delay-dependent manner. In particular, cannabinoids increase intrusion errors. These effects are more robust with the inhaled and intravenous route and correspond to peak drug levels.

CONCLUSIONS

This profile of effects suggests that cannabinoids impair all stages of memory including encoding, consolidation, and retrieval. Several mechanisms, including effects on long-term potentiation and long-term depression and the inhibition of neurotransmitter (GABA, glutamate, acetyl choline, dopamine) release, have been implicated in the amnestic effects of cannabinoids. Future research in humans is necessary to characterize the neuroanatomical and neurochemical basis of the memory impairing effects of cannabinoids, to dissect out their effects on the various stages of memory and to bridge the expanding gap between the humans and preclinical literature.

5-HT1A receptors are involved in the anxiolytic effect of Delta9-tetrahydrocannabinol and AM 404, the anandamide transport inhibitor, in Sprague-Dawley rats

The mechanism mediating the effects of cannabinoids on anxiety-related responses appear to involve cannabinoid CB1 and non-CB1 receptors. However, other neurotransmitters may play a role in such effect. This study shows evidence of an interaction between endocannabinoid system and serotonin (5-HT), 1A receptor subtype on anxiety-like behavior in Sprague-Dawley rats. The exogenous cannabinoid agonist, Delta9-tetrahydrocannabinol (THC), and N-(4-hydroxyphenyl)-arachidonylamide, the anandamide transporter inhibitor (AM 404) were evaluated in the elevated plus maze test. THC (0.075-0.75 mg/kg i.p.), given 30 min and AM 404 (0.75-1.25 mg/kg i. p.), given 60 min before the test, exhibited a dose-response anxiolytic effect evaluated in terms of increase in the percentage of total entries and time spent in the open and decrease of total entries and time spent in the closed arms. The anxiolytic effect obtained with the maximal active dose of both THC (0.75 mg/kg) and AM 404 (1.25 mg/kg) was blocked by the 5-HT1A receptor antagonist, N-[2-[4-(2-methoxyphenyl) piperazin-1-yl]ethyl]-N-pyridin-2-yl-cyclohexanecarboxamide dihydro chloride (WAY-100635 (300 microg/kg, s.c.), given 30 min before THC or 15 min before AM 404. The combination of an ineffective dose of THC (0.015 mg/kg) or AM 404 (0.015 mg/kg) on anxiety-related responses with an ineffective dose of the 5HT(1A) receptor agonist, 8-Hydroxy-2-(di-n-propylamino) tetralin hydrobromide (8-OH-DPAT) (7.5 microg/kg, i.p.), led to a synergistic effect. No interference with spontaneous motor activity, evaluated in an activity cage for 5 min, in rats given the drugs alone or in combination, was found. These data suggest that the anxiolytic effect produced by endo- and eso-cannabinoids is modulated by 5-HT1A receptors.

Effects of endocannabinoid neurotransmission modulators on brain stimulation reward

RATIONALE

The endogenous cannabinoid system is responsive to the neurobiological actions of Delta9-tetrahydrocannabinol (THC) and other cannabinoid ligands. While numerous studies have focused on the behavioral and pharmacological effects of THC and cannabinoid agonists in experimental animals, most recent work focuses on compounds that modulate endocannabinoid neurotransmission. However, the relevant studies concerning the ability of endocannabinoid modulators to modify reward processes in experimental animals remain rather scarce.

OBJECTIVES

The present study examined the effects of drugs modulating endocannabinoid neurotransmission on brain reward function using the rate-frequency curve shift paradigm of intracranial self-stimulation (ICSS).

METHODS

Animals were implanted with electrodes into the medial forebrain bundle (MFB). After brain stimulation reward thresholds stabilized, rats received intraperitoneal injections of the fatty acid amide hydrolase (FAAH) inhibitors phenylmethylsulfonyl fluoride (PMSF) (0, 15, 30, and 60 mg/kg) and URB-597 (0, 0.3, 1, and 3 mg/kg) and the selective anandamide reuptake inhibitor OMDM-2 (0, 3, 10, and 30 mg/kg).

RESULTS

The highest dose of URB-597 and OMDM-2 significantly increased the threshold frequency required for MFB ICSS, while PMSF increased the threshold frequency in all doses tested. The cannabinoid 1 (CB1) receptor antagonist SR141716A reversed the actions of URB-597 and OMDM-2, but not PMSF, without affecting reward thresholds by itself.

CONCLUSIONS

These results indicate that under the present experimental conditions endocannabinoid modulators do not exhibit reinforcing properties, but rather have inhibitory influence on reward processes. The anhedonic effects of URB-597 and OMDM-2, but not PMSF, observed at the highest doses in this study are probably mediated through direct CB1 receptor stimulation.

The alcohol-preferring AA and alcohol-avoiding ANA rats: neurobiology of the regulation of alcohol drinking

The AA (alko, alcohol) and ANA (alko, non-alcohol) rat lines were among the earliest rodent lines produced by bidirectional selection for ethanol preference. The purpose of this review is to highlight the strategies for understanding the neurobiological factors underlying differential alcohol-drinking behavior in these lines. Most early work evaluated functioning of the major neurotransmitter systems implicated in drug reward in the lines. No consistent line differences were found in the dopaminergic system either under baseline conditions or after ethanol challenges. However, increased opioidergic tone in the ventral striatum and a deficiency in endocannabinoid signaling in the prefrontal cortex of AA rats may comprise mechanisms leading to increased ethanol consumption. Because complex behaviors, such as ethanol drinking, are not likely to be controlled by single factors, system-oriented molecular-profiling strategies have been used recently. Microarray based expression analysis of AA and ANA brains and novel data-mining strategies provide a system biological view that allows us to formulate a hypothesis on the mechanism underlying selection for ethanol preference. Two main factors appear active in the selection: a recruitment of signal transduction networks, including mitogen-activated protein kinases and calcium pathways and involving transcription factors such as Creb, Myc and Max, to mediate ethanol reinforcement and plasticity. The second factor acts on the mitochondrion and most likely provides metabolic flexibility for alternative substrate utilization in the presence of low amounts of ethanol.

Antiobesity effects of the novel in vivo neutral cannabinoid receptor antagonist 5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-3-hexyl-1H-1,2,4-triazole – LH 21

The present study evaluates the pharmacological profile of the new neutral cannabinoid CB1 receptor antagonist 5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-3-hexyl-1H-1,2,4-triazole -LH-21- on feeding behavior and alcohol self-administration in rats, two behaviors inhibited by cannabinoid CB1 receptor antagonists. Administration of LH-21 (0.03, 0.3 and 3 mg/kg) to food-deprived rats resulted in a dose-dependent inhibition of feeding. Subchronic administration of LH-21 reduced food intake and body weight gain in obese Zucker rats. Acute effects on feeding were not associated with anxiety-like behaviors, or induction of complex motor behaviors such as grooming or scratching sequences, usually observed after central administration of cannabinoid receptor blockers with inverse agonist properties. LH-21 did not markedly reduce alcohol self-administration (30% reduction observed only at a high dose of 10 mg/kg). This pharmacological pattern partially overlaps that of the reference cannabinoid CB1 receptor antagonist N-piperidino-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methylpyrazole-3-carboxamide, SR141716A, (0.3, 1 and 3 mg/kg) that reduced feeding and alcohol self-administration with similar efficacy. In vitro analysis of blood-brain barrier permeability using a parallel artificial membrane permeation assay demonstrated that LH-21 has lower permeation through membranes than SR141716A. That was confirmed in vivo by studies showing lower potency of peripherally injected LH-21 when compared to SR141716A to antagonize motor depression induced by intracerebroventricular administration of the CB1 agonist CP55,940. The neutral antagonist profile and the lower penetration into the brain of LH-21 favour this class of antagonists with respect to reference inverse agonists for the treatment of obesity because they potentially will display reduced side effects.

Synthesis of a potential photoactivatable anandamide analog

A potential photoreactive analog of anandamide was synthesized via selective hydrogenation of a skipped tetrayne intermediate. This compound might be a useful tool to search for new cannabinoid receptors.

Implication of cannabinoids in neurological diseases

1. Preparations from Cannabis sativa (marijuana) have been used for many centuries both medicinally and recreationally. 2. Recent advances in the knowledge of its pharmacological and chemical properties in the organism, mainly due to Delta(9)-tetrahydrocannabinol, and the physiological roles played by the endocannabinoids have opened up new strategies in the treatment of neurological and psychiatric diseases. 3. Potential therapeutic uses of cannabinoid receptor agonists include the management of spasticity and tremor in multiple sclerosis/spinal cord injury, pain, inflammatory disorders, glaucoma, bronchial asthma, cancer, and vasodilation that accompanies advanced cirrhosis. CB(1) receptor antagonists have therapeutic potential in Parkinson's disease. 4. Dr. Julius Axelrod also contributed in studies on the neuroprotective actions of cannabinoids.

Targeting dopamine D2 and cannabinoid-1 (CB1) receptors in rat nucleus accumbens

The nucleus accumbens (Acb) shell and core are essential components of neural circuitry mediating the reward and motor effects produced by activation of dopamine D2 or cannabinoid-1 (CB1) receptors. D2 receptors can form heterodimeric complexes with cannabinoid-1 (CB1) receptors and are also involved in control of the availability of both dopamine and endocannabinoids. Thus, the subcellular locations of D2 and CB1 receptors with respect to each other are implicit to their physiological actions in the Acb. We used electron microscopic immunocytochemistry to determine these locations in the Acb shell and core of rat brain. In each region, many neuronal profiles showed endomembrane and plasmalemmal distributions of one or both receptors. Approximately one-third of the labeled profiles were somata and dendrites, some of which showed overlapping subcellular distributions of D2 and CB1 immunoreactivities. The remaining labeled profiles were small axons and axon terminals containing CB1 and/or D2 receptors. Of the labeled terminals forming recognizable synapses, approximately 20% of those containing CB1 receptors contacted D2-labeled dendrites, while conversely, almost 15% of those containing D2 receptors contacted CB1-labeled dendrites. These results provide the first ultrastructural evidence that D2 and CB1 receptors in the Acb shell and core have subcellular distributions supporting both intracellular associations and local involvement of D2 receptors in making available endocannabinoids that are active on CB1 receptors in synaptic neurons. These distributions have direct relevance to the rewarding and euphoric as well as motor effects produced by marijuana and by addictive drugs enhancing dopamine levels in the Acb.

Endocannabinoid system in Xenopus laevis development: CB1 receptor dynamics

This study investigates for the first time the dynamics of endocannabinoid system appearance during low vertebrate Xenopus laevis development. We observed that the CB1 gene started to be expressed during the organogenesis period (+/- 1 dpf, st. 28) and expression persisted throughout the three further stages analyzed. Attention was focused on the localization of the CB1 messenger that was found both at the central level (in romboencephalon and in olfactory placods) and at the peripheral level (in the gastrointestinal tract) at +/- 3 dpf (st. 41), +/- 4 dpf (st. 46) and +/- 12 dpf (st. 49). We also considered the synthesis of CB1 protein that occurred from st. 41 onwards and, from this stage, we tested the receptor functionality in response to anandamide using cytosensor microphysiometry. CB1 functionality increased with development at both central and peripheral level. These data provide sufficient evidence to encourage further analysis on endocannabinoid physiological roles during embryonic and larval X. laevis growth.

Virtual screening of novel CB2 ligands using a comparative model of the human cannabinoid CB2 receptor

To identify novel selective CB2 lead compounds, a comparative model of the CB2 receptor was constructed using the high-resolution bovine rhodopsin X-ray structure as a template. The CB2 model was utilized both in building the database queries and in filtering the hit compounds by a docking and scoring method. In G-protein activation assays, 1-isoquinolyl[3-(trifluoromethyl)phenyl]methanone (40, NRB 04079) was found to act as a selective agonist at the human CB2 receptor.

Inhibition of fatty acid amide hydrolase and monoacylglycerol lipase by the anandamide uptake inhibitor VDM11: evidence that VDM11 acts as an FAAH substrate

There is some dispute concerning the extent to which the uptake inhibitor VDM11 (N-(4-hydroxy-2-methylphenyl) arachidonoyl amide) is capable of inhibiting the metabolism of the endocannabinoid anandamide (AEA) by fatty acid amide hydrolase (FAAH). In view of a recent study demonstrating that the closely related compound AM404 (N-(4-hydroxyphenyl)arachidonylamide) is a substrate for FAAH, we re-examined the interaction of VDM11 with FAAH. In the presence of fatty acid-free bovine serum albumin (BSA, 0.125% w v(-1)), both AM404 and VDM11 inhibited the metabolism of AEA by rat brain FAAH with similar potencies (IC(50) values of 2.1 and 2.6 microM, respectively). The compounds were about 10-fold less potent as inhibitors of the metabolism of 2-oleoylglycerol (2-OG) by cytosolic monoacylglycerol lipase (MAGL). The potency of VDM11 towards FAAH was dependent upon the assay concentration of fatty acid-free bovine serum albumin (BSA). Thus, in the absence of fatty acid-free BSA, the IC(50) value for inhibition of FAAH was reduced by a factor of about two (from 2.9 to 1.6 microM). A similar reduction in the IC(50) value for the inhibition of membrane bound MAGL by both this compound (from 14 to 6 microM) and by arachidonoyl serinol (from 24 to 13 microM) was seen. An HPLC assay was set up to measure 4-amino-m-cresol, the hypothesised product of FAAH-catalysed VDM11 hydrolysis. 4-Amino-m-cresol was eluted with a retention time of approximately 2.4 min, but showed a time-dependent degradation to compounds eluting at peaks of approximately 5.6 and approximately 8 min. Peaks with the same retention times were also found following incubation of the membranes with VDM11, but were not seen when the membranes were preincubated with the FAAH inhibitors URB597 (3'-carbamoyl-biphenyl-3-yl-cyclohexylcarbamate) and CAY10401 (1-oxazolo[4,5-b]pyridin-2-yl-9-octadecyn-1-one) prior to addition of VDM11. The rate of metabolism of VDM11 was estimated to be roughly 15-20% of that for anandamide. It is concluded that VDM11 is an inhibitor of FAAH under the assay conditions used here, and that the inhibition may at least in part be a consequence of the compound acting as an alternative substrate.

Development of medications for alcohol use disorders: recent advances and ongoing challenges

During the past decade, efforts to develop medications for alcoholism have burgeoned. Three agents, disulfiram, naltrexone and acamprosate, are now approved in a large number of countries. Although many patients have benefited from existing medications, their effects are moderate, and some alcoholics fail to respond to them. A host of new agents are currently under active investigation. Critical barriers must be overcome to ensure that future efforts in the development of medications for alcohol use disorders reach full fruition. These challenges include: establishing key targets for drug discovery; validating animal and human screening models; and developing biomarkers to help predict treatment success. In addition, it is important to formulate methodological and statistical strategies to efficiently conduct alcohol pharmacotherapy trials; to specify genetic and phenotypic patient characteristics associated with efficacy and safety for lead compounds; to forge productive alliances among governmental agencies, the pharmaceutical industry and academic researchers to further drug development; and, ultimately and perhaps most difficult, to engage the practitioner community to incorporate medications into the alcohol treatment process.