CB1 receptor neutral antagonist treatment epigenetically increases neuropeptide Y expression and decreases alcohol drinking.

Alcohol consumption is mediated by several important neuromodulatory systems, including the endocannabinoid and neuropeptide Y (NPY) systems in the limbic brain circuitry. However, molecular mechanisms through which cannabinoid-1 (CB1) receptors regulate alcohol consumption are still unclear. Here, we investigated the role of the CB1 receptor-mediated downstream regulation of NPY via epigenetic mechanisms in the amygdala. Alcohol drinking behavior was measured in adult male C57BL/6J mice treated with a CB1 receptor neutral antagonist AM4113 using a two-bottle choice paradigm while anxiety-like behavior was assessed in the light-dark box (LDB) test. The CB1 receptor-mediated changes in the protein levels of phosphorylated cAMP-responsive element binding protein (pCREB), CREB binding protein (CBP), H3K9ac, H3K14ac and NPY, and the mRNA levels of Creb1, Cbp, and Npy were measured in amygdaloid brain structures. Npy-specific changes in the levels of acetylated histone (H3K9/14ac) and CBP in the amygdala were also measured. We found that the pharmacological blockade of CB1 receptors with AM4113 reduced alcohol consumption and, in an ethanol-naïve cohort, reduced anxiety-like behavior in the LDB test. Treatment with AM4113 also increased the mRNA levels of Creb1 and Cbp in the amygdala as well as the protein levels of pCREB, CBP, H3K9ac and H3K14ac in the central and medial nucleus of amygdala, but not in the basolateral amygdala. Additionally, AM4113 treatment increased occupancy of CBP and H3K9/14ac at the Npy gene promoter, leading to an increase in both mRNA and protein levels of NPY in the amygdala. These novel findings suggest that CB1 receptor-mediated CREB signaling plays an important role in the modulation of NPY function through an epigenetic mechanism and further support the potential use of CB1 receptor neutral antagonists for the treatment of alcohol use disorder.

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

BACKGROUND: While the etiology of depression is not clearly understood at the present time, this mental disorder is thought be a complex and multifactorial trait with important genetic and environmental contributing factors. METHODOLOGY/PRINCIPAL FINDINGS: The role of the endocannabinoid (eCB) system in depressive behavior was examined in Wistar Kyoto (WKY) rat strain, a genetic model of depression. Our findings revealed selective abnormalities in the eCB system in the brains of WKY rats compared to Wistar (WIS) rats. Immunoblot analysis indicated significantly higher levels of fatty acid amide hydrolase (FAAH) in frontal cortex and hippocampus of WKY rats with no alteration in the level of N-arachidonyl phosphatidyl ethanolamine specific phospholipase-D (NAPE-PLD). Significantly higher levels of CB1 receptor-mediated G-protein coupling and lower levels of anandamide (AEA) were found in frontal cortex and hippocampus of WKY rats. While the levels of brain derived neurotropic factor (BDNF) were significantly lower in frontal cortex and hippocampus of WKY rats compared to WIS rats, pharmacological inhibition of FAAH elevated BDNF levels in WKY rats. Inhibition of FAAH enzyme also significantly increased sucrose consumption and decreased immobility in the forced swim test in WKY rats. CONCLUSIONS/SIGNIFICANCE: These findings suggest a critical role for the eCB system and BDNF in the genetic predisposition to depressive-like behavior in WKY rats and point to the potential therapeutic utility of eCB enhancing agents in depressive disorder.

Cannabinoid receptor 1 signaling in embryo neurodevelopment.

In utero exposure to tetrahydrocannabinol, the psychoactive component of marijuana, is associated with an increased risk for neurodevelopmental defects in the offspring by interfering with the functioning of the endocannabinoid (eCB) system. At the present time, it is not clearly known whether the eCB system is present before neurogenesis. Using an array of biochemical techniques, we analyzed the levels of CB1 receptors, eCBs (AEA and 2-AG), and the enzymes (NAPE-PLD, DAGLα, DAGLß, MAGL, and FAAH) involved in the metabolism of the eCBs in chick and mouse models during development. The findings demonstrate the presence of eCB system in early embryo before neurogenesis. The eCB system might play a critical role in early embryogenesis and there might be adverse developmental consequences of in utero exposure to marijuana and other drugs of abuse during this period.

Innate difference in the endocannabinoid signaling and its modulation by alcohol consumption in alcohol-preferring sP rats.

The present study was undertaken to examine whether genetically predetermined differences in components of the endocannabinoid system were present in the brain of Sardinian alcohol-preferring (sP) and Sardinian alcohol-non-preferring (sNP) rats, a pair of rat lines selectively bred for opposite alcohol preference. The effects of acquisition and maintenance of alcohol drinking, alcohol withdrawal, and alcohol re-exposure on the endocannabinoid system was also assessed in the striatum of sP rats. The findings revealed significantly higher density of the CB1 receptors and levels of CB1 receptor mRNA, CB1 receptor-mediated G-protein coupling, and endocannabinoids in the cerebral cortex, hippocampus and striatum of alcohol-naive sP rats than sNP rats. A significantly lower expression of mFAAH enzyme was evident in the hippocampus of alcohol-naive sP rats. Alcohol drinking (during both acquisition and maintenance phases) in sP rats resulted in a significant reduction in striatal CB1 receptor-mediated G-protein coupling whereas alcohol withdrawal attenuated this effect. Alcohol consumption was also associated with markedly increased levels of endocannabinoids in the striatum. Co-administration of the CB1 receptor antagonist, rimonabant (SR141716A) reduced alcohol intake, and reversed alcohol-induced changes in CB1 receptor-mediated G-protein activation. These findings provided a new insight into a potential genetic basis of excessive alcohol consumption, suggesting innate differences in the endocannabinoid system might be associated with higher alcohol preference in sP rats. The data also indicate a modulation of CB1 receptor-mediated signaling following alcohol consumption, and further strengthen the potential of the endocannabinoid system as a target for the treatment of alcohol related behaviors.

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

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

A cannabinoid analogue of Delta9-tetrahydrocannabinol disrupts neural development in chick.

Marijuana is the most commonly abused illicit drug by pregnant women. Its major psychoactive constituent, Delta(9)-THC (Delta(9)-tetrahydrocannabinol), crosses the placenta and accumulates in the foetus, potentially harming its development. In humans, marijuana use in early pregnancy is associated with miscarriage, a fetal alcohol-like syndrome, as well as learning disabilities, memory impairment, and ADHD in the offspring. Classical studies in the 1970 s have reached disparate conclusions as to the teratogenic effects of cannabinoids in animal models. Further, there is very little known about the immediate effects of Delta(9)-THC on early embryogenesis. We have used the chick embryo as a model in order to characterize the effects of a water-soluble Delta(9)-THC analogue, O-2545, on early development. Embryos were exposed to the drug (0.035 to 0.35 mg/ml) at gastrulation and assessed for morphological defects at stages equivalent to 9-14 somites. We report that O-2545 impairs the formation of brain, heart, somite, and spinal cord primordia. Shorter incubation times following exposure to the drug show that O-2545 interferes with the initial steps of head process and neural plate formation. Our results indicate that the administration of the cannabinoid O-2545 during early embryogenesis results in embryotoxic effects and serves to illuminate the risks of marijuana exposure during the second week of pregnancy, a time point at which most women are unaware of their pregnancies.

Genetic and pharmacological manipulations of the CB(1) receptor alter ethanol preference and dependence in ethanol preferring and nonpreferring mice.

Recent studies have indicated a role for the endocannabinoid system in ethanol-related behaviors. This study examined the effect of pharmacological activation, blockade, and genetic deletion of the CB(1) receptors on ethanol-drinking behavior in ethanol preferring C57BL/6J (B6) and ethanol nonpreferring DBA/2J (D2) mice. The deletion of CB(1) receptor significantly reduced the ethanol preference. Although the stimulation of the CB(1) receptor by CP-55,940 markedly increased the ethanol preference, this effect was found to be greater in B6 than in D2 mice. The antagonism of CB(1) receptor function by SR141716A led to a significant reduction in voluntary ethanol preference in B6 than D2 mice. A significant lower hypothermic and greater sedative response to acute ethanol administration was observed in both the strains of CB(1) -/- mice than wild-type mice. Interestingly, genetic deletion and pharmacological blockade of the CB(1) receptor produced a marked reduction in severity of handling-induced convulsion in both the strains. The radioligand binding studies revealed significantly higher levels of CB(1) receptor-stimulated G-protein activation in the striatum of B6 compared to D2 mice. Innate differences in the CB(1) receptor function might be one of the contributing factors for higher ethanol drinking behavior. The antagonists of the CB(1) receptor may have therapeutic potential in the treatment of ethanol dependence.

Manipulation of fatty acid amide hydrolase functional activity alters sensitivity and dependence to ethanol.

The aim of this study was to examine the role of fatty acid amide hydrolase (FAAH) on ethanol sensitivity, preference, and dependence. The deletion of FAAH gene or the inhibition of FAAH by carbamoyl-biphenyl-3-yl-cyclohexylcarbamate (URB597) (0.1 mg/kg) markedly increased the preference for ethanol. The study further reveals that URB597 specifically acts through FAAH and that cannabinoid-1 (CB(1)) receptor is critical for N-arachidonoyl ethanolamide (AEA) mediated ethanol-reinforced behavior as revealed by lack of URB597 effect in both FAAH and CB(1)-/- mice compared with vehicle-treated -/- mice. The FAAH -/- mice displayed a lower sensitivity to hypothermic and sedative effects to acute ethanol challenge. The FAAH -/- mice also exhibited a reduction in the severity of handling-induced convulsions following withdrawal from chronic ethanol exposure. The CB(1) receptor and proenkephalin gene expressions, and CB(1) receptor and mu-opioid (MO) receptor-mediated G-protein activation were found to be significantly lower in the caudate-putamen, nucleus accumbens core and shell of FAAH -/- than +/+ mice. Interestingly, the MO receptor-stimulated G-protein signaling was greater in the striatum of FAAH -/- than +/+ mice following voluntary ethanol consumption. These findings suggest that an elevation in the AEA content and its action on the limbic CB(1) receptor and MO receptor might contribute to ethanol-reinforced behavior. Treatment with drugs that decrease AEA tone might prove useful in reducing excessive ethanol consumption.

The endocannabinoid 2-arachidonoyl glycerol induces death of hepatic stellate cells via mitochondrial reactive oxygen species.

The endocannabinoid system is an important regulator of hepatic fibrogenesis. In this study, we determined the effects of 2-arachidonoyl glycerol (2-AG) on hepatic stellate cells (HSCs), the main fibrogenic cell type in the liver. Culture-activated HSCs were highly susceptible to 2-AG-induced cell death with >50% cell death at 10 microM after 18 h of treatment. 2-AG-induced HSC death showed typical features of apoptosis such as PARP- and caspase 3-cleavage and depended on reactive oxygen species (ROS) formation. Confocal microscopy revealed mitochondria as primary site of ROS production and demonstrated mitochondrial depolarization and increased mitochondrial permeability after 2-AG treatment. 2-AG-induced cell death was independent of cannabinoid receptors but required the presence of membrane cholesterol. Primary hepatocytes were resistant to 2-AG-induced ROS induction and cell death but became susceptible after GSH depletion suggesting antioxidant defenses as a critical determinant of 2-AG sensitivity. Hepatic levels of 2-AG were significantly elevated in two models of experimental fibrogenesis and reached concentrations that are sufficient to induce death in HSCs. These findings suggest that 2-AG may act as an antifibrogenic mediator in the liver by inducing cell death in activated HSCs but not hepatocytes.

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.

Investigation on the relationship between cannabinoid CB1 and opioid receptors in gastrointestinal motility in mice.

1. This study investigated whether (a) cannabinoid CB(1) receptor knockout (CB(1)(-/-)) mice displayed altered gastrointestinal transit and (b) cannabinoid CB(1) and opioid receptors functionally interact in the regulation of gastrointestinal transit. 2. Gastrointestinal transit was assessed by the Whole Gastrointestinal Transit, measuring the excretion time of an intragastrically administered marker (whole intestine), and the Upper Gastrointestinal Transit, measuring the distance covered by the marker in the small intestine. 3. CB(1)(-/-) and homozygous CB(1)(+/+) (CB(1)(+/+)) mice did not differ in both whole gut and small intestine transit. CB(1)(-/-) and CB(1)(+/+) mice were equally responsive to the inhibitory effect of morphine (10 mg kg(-1)) and loperamide (3 mg kg(-1)) on whole gut transit.4. Additionally, in CD1 mice the cannabinoid CB(1) receptor antagonist, rimonabant (0-0.5 mg kg(-1)), failed to block the inhibitory effect of morphine (0-1.25 mg kg(-1)) and loperamide (0-0.5 mg kg(-1)) on transit in small and whole intestine. Similarly, the opioid receptor antagonists, naloxone (0-1 mg kg(-1)) and naltrexone (0-10 mg kg(-1)), failed to block the inhibitory effect of the cannabinoid WIN 55,212-2 (0-3 mg kg(-1)) on transit in small and whole intestine.5. These results suggest that (a) compensatory mechanisms likely developed in CB(1)(-/-) mice to overcome the lack of inhibitory function of endocannabinoid system; (b) cannabinoid and opioid receptor systems did not interact in regulating gastrointestinal transit in mice.

Effect of chronic ethanol exposure and its withdrawal on the endocannabinoid system.

The present study investigated the effect of ethanol (EtOH) exposure and its withdrawal on the central endocannabinoid system utilizing an EtOH vapor inhalation model, which is known to produce functional tolerance and dependence to EtOH. Swiss Webster mice (n=24) were exposed to EtOH vapors for 72h. Mice were sacrificed after 72h following EtOH exposure (n=12) and 24h after its withdrawal (n=12). Radioligand binding assays were performed to measure the density of CB(1) receptor and CB(1) receptor agonist-stimulated [(35)S]GTPgammaS binding in crude synaptic membranes isolated from the cortex, hippocampus, striatum and cerebellum. The density of CB(1) receptor was significantly decreased (31-39%) in all the brain regions when compared to the control group. The CB(1) receptor-stimulated G(i/o) protein activation was also found to be decreased (29-40%) in these brain regions of EtOH exposed mice. Recovery of the CB(1) receptor density, in addition to, the CB(1) receptor-mediated G-protein activation was observed after 24h withdrawal from EtOH. The levels of cortical anandamide, which was significantly increased (147%) by EtOH exposure, returned to basal levels after 24h of withdrawal from EtOH exposure. A significant reduction (21%) in the activity of fatty acid amide hydrolase was found in the cortex of EtOH administered mice. Taken together, the neuroadaptation in the EC system may have a potential role in development of tolerance and dependence to EtOH.

Cannabinoid-1 receptor: a novel target for the treatment of neuropsychiatric disorders.

G-protein-coupled receptor (GPCR)-mediated signalling is the most widely used signalling mechanism in cells, and its regulation is important for various physiological functions. The cannabinoid-1 (CB(1)) receptor, a GPCR, has been shown to play a critical role in neural circuitries mediating motivation, mood and emotional behaviours. Several recent studies have indicated that impairment of CB(1) receptor-mediated signalling may play a critical role in the pathophysiology of various neuropsychiatric disorders. In this article, the authors briefly review literature relating to the role played by the endocannabinoid system in various neuropsychiatric disorders, and the CB(1) receptor as a potential therapeutic target for the treatment of alcoholism, depression, anxiety and schizophrenia.

Increased ethanol consumption and preference and decreased ethanol sensitivity in female FAAH knockout mice.

Previous studies have shown that mice lacking cannabinoid (CB1) receptor gene consume markedly reduced levels of ethanol. Mice lacking the enzyme fatty acid amidohydrolase (FAAH) are severely impaired in their ability to degrade anandamide (AEA) and therefore represent a unique animal model in which to examine the function of AEA in vivo on ethanol-drinking behavior. In the current study, FAAH(-/-) mice were tested for ethanol, saccharin or quinine consumption and preference. Ethanol-induced hypothermia, and sleep time were used to evaluate the sensitivity to acute effects of ethanol. Ethanol intake and preference were increased only in female FAAH(-/-) mice. No significant difference in saccharin or quinine consumption or preference was observed between genotypes. Female FAAH(-/-) mice were less sensitive to the hypothermic and sedative/hypnotic effects of acute ethanol. Supersensitivity to exogenous AEA was noted in both male and female FAAH(-/-) mice. Following voluntary ethanol consumption, CB1 receptor levels and function were down-regulated in male FAAH(+/+), FAAH(-/-), and female FAAH(+/+) mice but not in female FAAH(-/-) mice. Our results suggest that absence of an effect in male mice indicates a sex-linked mechanism that is secondary (or modulatory) to FAAH function. Thus, the data suggest that FAAH may be indirectly related to ethanol intake and sensitivity and central endocannabinoidergic-mediated pathways may regulate ethanol consumption.

Pharmacological manipulation of CB1 receptor function alters development of tolerance to alcohol.

AIMS: The current study investigated the efficacy of CB1 receptor-targeted drugs on the development and expression of tolerance to alcohol (EtOH). METHODS: An EtOH-inhalation model was used to induce tolerance, as measured by EtOH-induced sedation and hypothermia after a 24 h withdrawal period. Two drug treatment procedures, (i) co-treatment with EtOH and (ii) acute drug administration following chronic EtOH treatment, were used to test the efficacy of CB1 receptor manipulations on EtOH tolerance. RESULTS: The effects of the CB1 receptor agonist CP-55,940 varied depending on paradigm and behavioural measure. Chronic CP-55,940 co-treatment blocked tolerance to EtOH-induced hypothermia but not to the sedative effect (sleep time) in EtOH-exposed mice. However, chronic CP-55,940 administration alone resulted in tolerance to the sedative effect of a challenge dose of EtOH in control mice. Acute CP-55,940 administration after chronic alcoholization blocked the development of tolerance to EtOH-induced sedation compared to the EtOH alone exposed group, but induced tolerance to the hypothermic effects of EtOH in control mice. Chronic blockade of CB1 receptor function by SR141716A resulted in tolerance to both the sedative and hypothermic effects of EtOH in control mice, but had no effect on EtOH-exposed mice. CONCLUSIONS: The data support a role for the endocannabinoid (EC) system in EtOH tolerance/dependence and suggest that drugs targeted against EC system could be therapeutically useful in treating alcohol-related disorders.

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

Several natural lipids have emerged as candidate modulators of central nervous system (CNS) functions. Fatty acid amides and their coupled signaling pathways are known to regulate several physiological and behavioral processes. Recent studies from our laboratory and others also have implicated endogenous marijuana-like brain constituents, endocannabinoids (ECs), and cannabinoid-1 (CB1) receptors in the neural circuitry that mediate drug addiction and neuropsychiatric disorders. Neuroadaptation to chronic ethanol (EtOH) has been shown to involve changes in the EC system. These changes include alterations in the synthesis of EC, their precursors, as well as density and coupling efficacy of CB1 receptors. The evidence for the participation of the EC system in the pathophysiology of various neuropsychiatric disorders is just beginning to evolve. It is of great interest to explore the components of EC system in different areas of the CNS for further understanding of its role in health and disease. This article presents a comprehensive overview of the currently available literature pertaining to the role of the EC system in alcoholism, schizophrenia, depression and/or suicide.

2-PMPA, a NAAG peptidase inhibitor, attenuates magnetic resonance BOLD signals in brain of anesthetized mice: evidence of a link between neuron NAAG release and hyperemia.

N-acetylaspartylglutamate (NAAG), a dipeptide derivative of N-acetylaspartate (NAA) and glutamate (Glu), is present in neurons. Upon neurostimulation, NAAG is exported to astrocytes where it activates a specific metabotropic Glu surface receptor (mGluR3), and is then hydrolyzed by an astrocyte-specific enzyme, NAAG peptidase, liberating Glu, which can then be taken up by the astrocyte. NAAG is a selective mGluR3 agonist, one of several mGluRs that, when activated, triggers Ca2+ waves that spread to astrocytic endfeet in contact with the vascular system, where a secondary release of vasoactive agents induces a focal hyperemic response providing increased oxygen and nutrient availability to the stimulated neurons. Changes in blood oxygen levels can be assessed in vivo using a blood oxygenation level-dependent (BOLD) magnetic resonance imaging technique that reflects a paramagnetic effect of deoxyhemoglobin. In this study we used the competitive NAAG peptidase inhibitor 2-(phosphonomethyl) pentanedioic acid (2-PMPA) as a probe to interrupt the NAAG-mGluR3- Glu-astrocyte Ca2+ activation sequence. Using this probe, we investigated the relationship between release of the endogenous neuropeptide NAAG and brain blood oxygenation levels, as measured by changes in BOLD signals. In an anesthetized mouse, using an overtly nontoxic dose of 2-PMPA of 250 mg/kg i.p., there was an initial global BOLD signal increase of about 3% above control, lasting about 4 min, followed by a decrease from control of about 4%, sustained over a 32.5-min period of the drug test procedure. Similar changes, but of reduced magnitude and duration, were observed at a dose of 167 mg/kg. The 2-PMPA-induced decreases in BOLD signals appear to indicate that blood deoxyhemoglobin is elevated when endogenous NAAG cannot be hydrolyzed, thus linking the efflux of NAAG from neurons and its hydrolysis by astrocytes to hyperemic oxygenation responses in brain.

Elevated levels of endocannabinoids and CB1 receptor-mediated G-protein signaling in the prefrontal cortex of alcoholic suicide victims.

BACKGROUND: Alcoholism is often comorbid with mood disorders and suicide. We recently reported an upregulation of CB(1) receptor-mediated signaling in the dorsolateral prefrontal cortex (DLPFC) of subjects with major depression who died by suicide. In the present study, we sought to determine whether the changes in depressed suicides would also be present in alcoholic suicides and whether the endocannabinoid (EC) system plays a role in suicide in alcoholism. METHODS: The density of CB(1) receptor and its mediated [(35)S]GTP gamma S signaling were measured in the DLPFC of alcoholic suicides (AS) (n = 11) and chronic alcoholics (CA) (n = 11). The levels of ECs were measured by a liquid chromatograph/mass spectrometry. RESULTS: The CB(1) receptor density was higher in AS compared with the CA group in the DLPFC. Western blot analysis confirmed a greater immunoreactivity of the CB(1) receptor in AS. The CB(1) receptor-mediated [(35)S]GTP gamma S binding indicated a greater signaling in AS. Higher levels of N-arachidonyl ethanolamide and 2-arachidonylglycerol were observed in the DLPFC of AS. CONCLUSIONS: The elevated levels of ECs, CB(1) receptors, and CB(1) receptor-mediated [(35)S]GTP gamma S binding strongly suggest a hyperactivity of endocannabinoidergic signaling in AS. EC system may be a novel therapeutic target for the treatment of suicidal behavior.

Role of the endocannabinoid system in the development of tolerance to alcohol.

The present review evaluates the evidence that the endocannabinoid system plays in the development of tolerance to alcohol. The identification of a G-protein-coupled receptor, namely, the cannabinoid receptor (CB(1) receptor), which was activated by Delta(9)-tetrahydrocannabinol (Delta(9)-THC), the major psychoactive component of marijuana, led to the discovery of endogenous cannabinoid agonists. Until now, four fatty acid derivatives identified to be arachidonylethanolamide (AEA), 2-arachidonylglycerol (2-AG), 2-arachidonylglycerol ether (noladin ether) and virodhamine have been isolated from both nervous and peripheral tissues. Both AEA and 2-AG have been shown to mimic the pharmacological and behavioural effects of Delta(9)-THC. The role of the endocannabinoid system in the development of tolerance to alcohol was not known until recently. Recent studies from our laboratory have implicated for the first time a role for the endocannabinoid system in development of tolerance to alcohol. Chronic alcohol treatment has been shown to down-regulate CB(1) receptors and its signal transduction. The observed downregulation of CB(1) receptor function results from the persistent stimulation of the receptors by AEA and 2-AG, the synthesis of which has been shown to be increased by chronic alcohol treatment. The enhanced formation of endocannabinoids may subsequently influence the release of neurotransmitters. It was found that the DBA/2 mice, known to avoid alcohol intake, have significantly reduced CB(1) receptor function in the brain, consistent with other studies in which the CB(1) receptor antagonist SR 141716A has been shown to block voluntary alcohol intake in rodents. Similarly, activation of the CB(1) receptor system promoted alcohol craving, suggesting a role for the CB(1) receptor gene in excessive alcohol drinking behaviour and development of alcoholism. Ongoing investigations may lead to a better understanding of the mechanisms underlying the development of tolerance to alcohol and to develop therapeutic strategies to treat alcoholism.

Role of endocannabinoids and cannabinoid CB1 receptors in alcohol-related behaviors.

This review presents the remarkable research during the past several years indicating that some of the pharmacological and behavioral effects of alcohol, including alcohol drinking and alcohol-preferring behavior, are mediated through one of the most abundant neurochemical systems in the central nervous system, the endocannabinoid signaling system. The advances, with the discovery of specific receptors and the existence of naturally occurring cannabis-like substances in the mammalian system and brain, have helped in understanding the neurobiological basis for drugs of abuse, including alcoholism. The cDNA and genomic sequences encoding G-protein-coupled cannabinoid receptors (CB1 and CB2) from several species have now been cloned. This has facilitated discoveries of endogenous ligands (endocannabinoids). To date, two fatty acid derivatives characterized to be arachidonylethanolamide and 2-arachidonylglycerol have been isolated from both nervous and peripheral tissues. Both these compounds have been shown to mimic the pharmacological and behavioral effects of Delta9-tetrahydrocannabinol, the psychoactive component of marijuana. The involvement of the endocannabinoid signaling system in tolerance development to drugs of abuse, including alcohol, were unknown until recently. Studies from our laboratory demonstrated for the first time the downregulation of CB1 receptor function and its signal transduction by chronic alcohol. The observed downregulation of CB1 receptor binding and its signal transduction results from the persistent stimulation of receptors by the endogenous CB1 receptor agonists arachidonylethanolamide and 2-arachidonylglycerol, the synthesis of which is increased by chronic alcohol treatment. The deletion of CB1 receptor has recently been shown to block voluntary alcohol intake in mice, which is consistent with our previous findings where the DBA/2 mice known to avoid alcohol intake had significantly reduced brain CB1 receptor function. These findings suggest a role for the CB1 receptor gene in excessive alcohol drinking behavior and development of alcoholism. Ongoing investigations may lead to the development of potential therapeutic agents to modulate the endocannabinoid signaling system, which will be helpful for the treatment of alcoholism.