Blockade Of Cannabinoid CB1 Receptors Research Articles

Cannabinoid reward and aversion effects in the posterior ventral tegmental area are mediated through dissociable opiate receptor subtypes and separate amygdalar and accumbal dopamine receptor substrates.

The ventral tegmental area (VTA) and its projections to the basolateral amygdala (BLA) and nucleus accumbens (NAc) are critical for cannabinoid-related motivational effects. Cannabinoid CB1 receptor (CB1R) transmission modulates VTA dopamine (DA) neuron activity and previous reports demonstrate anatomically segregated effects of CB1R transmission in the VTA. However, the underlying pharmacological and anatomical regions responsible for these effects are currently unknown. The objective of the study is to characterize the motivational effects of localized anterior vs. posterior intra-VTA activation vs. blockade of CB1R transmission and the potential role of intra-BLA and intra-NAc DA transmission in these phenomena. Using a conditioned place preference (CPP) procedure, we administered a CB1 agonist (WIN-55,212-2) or antagonist (AM 251) into the posterior VTA (pVTA) or anterior VTA (aVTA) of rats, combined with intra-BLA or intra-NAc DA receptor blockade and intra-VTA co-administration of selective mu vs. kappa opiate-receptor antagonists. Intra-pVTA CB1R activation produced robust rewarding effects through a mu-opiate receptor mechanism whereas CB1R blockade produced conditioned place aversions (CPA) through a kappa-opiate receptor substrate. In contrast, modulation of aVTA CB1R transmission produced no observable effects. Intra-BLA DA receptor blockade prevented the rewarding effects of pVTA CB1R activation, but had no effects on CB1R blockade-induced aversions. In contrast, intra-NAc DA receptor blockade selectively blocked the aversive effects of pVTA CB1R antagonism. Activation vs. blockade of CB1R transmission in the posterior VTA produces bivalent rewarding or aversive effects through separate mu vs. kappa-opiate receptor substrates. These dissociable effects depend on separate DA receptor transmission substrates in the BLA or NAc, respectively.

Blockade of Cannabinoid CB1 receptor attenuates the acquisition of morphine-induced conditioned place preference along with a downregulation of ERK, CREB phosphorylation, and BDNF expression in the nucleus accumbens and hippocampus

Cannabinoid CB1 receptor (CB1R) is highly expressed in the mesocorticolimbic system and associated with drug craving and relapse. Clinical trials suggest that CB1R antagonists may represent new therapies for drug addiction. However, the downstream signaling of CB1R is not fully elucidated. In the present study, we investigated the relationship between CB1R and the extracellular signal-regulated kinase (ERK), cAMP response element-binding protein (CREB), brain-derived neurotrophic factor (BDNF) signaling in the nucleus accumbens (NAc) and hippocampus in morphine-induced conditioned place preference (CPP), which is used to assess the morphine-induced reward memory. The protein level of CB1R, ERK, CREB, and BDNF were detected by western blotting. Additionally, a CB1R antagonist, AM251, was used to study whether blockade of CB1R altered the CPP and above-mentioned molecules. We found an increase of CB1R expression in the NAc and hippocampus of the mice following morphine CPP, but not those after repeated morphine in home cage without context exposure (NO-CPP). Both morphine CPP and NO-CPP induced an upregulation of ERK, CREB phosphorylation and BDNF expression. Furthermore, pretreatment with AM251 before morphine attenuated the CPP acquisition and CB1R expression as well as the activation of ERK-CREB-BDNF cascade. Collectively, these findings demonstrate that (1) Repeated morphine with context exposures but not merely the pharmacological effects of morphine increased CB1R expression both in the NAc and hippocampus. (2) CB1R antagonist mediated blockade of ERK-CREB-BDNF signaling activation in the NAc and hippocampus may be an important mechanism underlying the attenuation of morphine CPP.

Bi-directional cannabinoid signalling in the basolateral amygdala controls rewarding and aversive emotional processing via functional regulation of the nucleus accumbens.

Functional connections between the basolateral amygdala (BLA) and nucleus accumbens (NAc) are involved critically in opiate-reward processing. In the BLA, inhibitory GABAergic substrates are inhibited by cannabinoid CB1 receptor (CB1R) activation and can modulate BLA projections to various limbic regions, including the NAc. However, the potential role of CB1R transmission in the regulation of opiate-related memory formation via the BLA → NAc circuit is not understood. Using an unbiased conditioned place preference paradigm in rats, we examined the effects of intra-BLA CB1R modulation by either direct pharmacological activation or blockade of CB1R transmission. We report that intra-BLA CB1R activation switches normally rewarding effects of morphine into strongly aversive effects. In contrast, CB1R blockade strongly potentiates normally subreward threshold effects of morphine. Next, using targeted microinfusions of an NMDA receptor antagonist to either the core or shell (NASh) subdivisions of the NAc, we found that selective blockade of NMDA transmission in the NA shell, but not core, prevented both intra-BLA CB1 blockade-mediated opiate reward potentiation and CB1 activation-mediated aversion effects. Finally, using multi-unit, in vivo electrophysiological recordings in the NASh, we report that the ability of intra-BLA CB1R modulation to control opiate reward salience and motivational valence is associated with distinct reward or aversion neuronal activity patterns and bi-directional regulation of intra-NASh fast-spiking interneurons versus medium spiny neurons. These findings identify a unique mechanism whereby bi-directional BLA CB1R transmission can regulate opiate-related motivational processing and control affective states through functional modulation of mesolimbic neuronal activity.

Major dorsoventral differences in the modulation of the local CA1 hippocampal network by NMDA, mGlu5, adenosine A2A and cannabinoid CB1 receptors

Recent research points to diversification in the local neuronal circuitry between dorsal (DH) and ventral (VH) hippocampus that may be involved in the large-scale functional segregation along the long axis of the hippocampus. Here, using CA1 field recordings from rat hippocampal slices, we show that activation of N-methyl-d-aspartate receptors (NMDARs) reduced excitatory transmission more in VH than in DH, with an adenosine A1 receptor-independent mechanism, and reduced inhibition and enhanced postsynaptic excitability only in DH. Strikingly, co-activation of metabotropic glutamate receptor-5 (mGluR5) with NMDAR, by CHPG and NMDA respectively, strongly potentiated the effects of NMDAR in DH but had not any potentiating effect in VH. Furthermore, the synergistic actions in DH were occluded by blockade of adenosine A2A receptors (A2ARs) by their antagonist ZM 241385 demonstrating a tonic action of these receptors in DH. Exogenous activation of A2ARs by 4-[2-[[6-amino-9-(N-ethyl-β-D-ribofuranuronamidosyl)-9H-purin-2-yl]amino]ethyl]benzenepropanoic acid hydrochloride (CGS 21680) did not change the effects of mGluR5–NMDAR co-activation in either hippocampal pole. Importantly, blockade of cannabinoid CB1 receptors (CB1Rs) by their antagonist 1-(2,4-dichlorophenyl)-5-(4-iodophenyl)-4-methyl-N-4-morpholinyl-1H-pyrazole-3-carboxamide (AM 281) restricted the synergistic actions of mGluR5–NMDARs on excitatory synaptic transmission and postsynaptic excitability and abolished their effect on inhibition. Furthermore, AM 281 increased the excitatory transmission only in DH indicating that CB1Rs were tonically active in DH but not VH. Removing the magnesium ions from the perfusion medium neither stimulated the interaction between mGluR5 and NMDAR in VH nor augmented the synergy of the two receptors in DH. These findings show that the NMDAR-dependent modulation of fundamental parameters of the local neuronal network, by mGluR5, A2AR and CB1R, markedly differs between DH and VH. We propose that the higher modulatory role of A2AR and mGluR5, in combination with the role of CB1Rs, provide DH with higher functional flexibility of its NMDARs, compared with VH.

Pharmacological Blockade of Cannabinoid CB1 Receptors in Diet-Induced Obesity Regulates Mitochondrial Dihydrolipoamide Dehydrogenase in Muscle.

Cannabinoid CB1 receptors peripherally modulate energy metabolism. Here, we investigated the role of CB1 receptors in the expression of glucose/pyruvate/tricarboxylic acid (TCA) metabolism in rat abdominal muscle. Dihydrolipoamide dehydrogenase (DLD), a flavoprotein component (E3) of α-ketoacid dehydrogenase complexes with diaphorase activity in mitochondria, was specifically analyzed. After assessing the effectiveness of the CB1 receptor antagonist AM251 (3 mg kg-1, 14 days) on food intake and body weight, we could identified seven key enzymes from either glycolytic pathway or TCA cycle—regulated by both diet and CB1 receptor activity—through comprehensive proteomic approaches involving two-dimensional electrophoresis and MALDI-TOF/LC-ESI trap mass spectrometry. These enzymes were glucose 6-phosphate isomerase (GPI), triosephosphate isomerase (TPI), enolase (Eno3), lactate dehydrogenase (LDHa), glyoxalase-1 (Glo1) and the mitochondrial DLD, whose expressions were modified by AM251 in hypercaloric diet-induced obesity. Specifically, AM251 blocked high-carbohydrate diet (HCD)-induced expression of GPI, TPI, Eno3 and LDHa, suggesting a down-regulation of glucose/pyruvate/lactate pathways under glucose availability. AM251 reversed the HCD-inhibited expression of Glo1 and DLD in the muscle, and the DLD and CB1 receptor expression in the mitochondrial fraction. Interestingly, we identified the presence of CB1 receptors at the membrane of striate muscle mitochondria. DLD over-expression was confirmed in muscle of CB 1 -/- mice. AM251 increased the pyruvate dehydrogenase and glutathione reductase activity in C2C12 myotubes, and the diaphorase/oxidative activity in the mitochondria fraction. These results indicated an up-regulation of methylglyoxal and TCA cycle activity. Findings suggest that CB1 receptors in muscle modulate glucose/pyruvate/lactate pathways and mitochondrial oxidative activity by targeting DLD.

Are cannabidiol and Δ(9) -tetrahydrocannabivarin negative modulators of the endocannabinoid system? A systematic review.

Based upon evidence that the therapeutic properties of Cannabis preparations are not solely dependent upon the presence of Δ(9) -tetrahydrocannabinol (THC), pharmacological studies have been recently carried out with other plant cannabinoids (phytocannabinoids), particularly cannabidiol (CBD) and Δ(9) -tetrahydrocannabivarin (THCV). Results from some of these studies have fostered the view that CBD and THCV modulate the effects of THC via direct blockade of cannabinoid CB1 receptors, thus behaving like first-generation CB1 receptor inverse agonists, such as rimonabant. Here, we review in vitro and ex vivo mechanistic studies of CBD and THCV, and synthesize data from these studies in a meta-analysis. Synthesized data regarding mechanisms are then used to interpret results from recent pre-clinical animal studies and clinical trials. The evidence indicates that CBD and THCV are not rimonabant-like in their action and thus appear very unlikely to produce unwanted CNS effects. They exhibit markedly disparate pharmacological profiles particularly at CB1 receptors: CBD is a very low-affinity CB1 ligand that can nevertheless affect CB1 receptor activity in vivo in an indirect manner, while THCV is a high-affinity CB1 receptor ligand and potent antagonist in vitro and yet only occasionally produces effects in vivo resulting from CB1 receptor antagonism. THCV has also high affinity for CB2 receptors and signals as a partial agonist, differing from both CBD and rimonabant. These cannabinoids illustrate how in vitro mechanistic studies do not always predict in vivo pharmacology and underlie the necessity of testing compounds in vivo before drawing any conclusion on their functional activity at a given target.

Differential blood pressure response in normotensive rats and rats with angiotensin II‐dependent hypertension following systemic cannabinoid CB1 receptor blockade (1140.11)

Evidence for interactions between the endocannabinoid (ECS) and the renin‐angiotensin (RAS) systems in brain and vasculature is emerging. In transgenic (mRen2)27 rats, an angiotensin (Ang) II‐dependent model of hypertension involving excess sympathetic nervous system activity (SNS), acute systemic blockade of CB1 cannabinoid receptors by the CB1‐selective antagonist SR141716A (SR; 10 mg/kg orally; n = 5) significantly reduced systolic blood pressure (SBP) from 176 ± 3 mmHg baseline to 134 ± 3 mmHg after 90 min (P < 0.001). SBP showed evidence of recovery after 24 h but remained significantly reduced at 146 ± 5 mmHg (P < 0.01) compared to baseline. Plasma collected at 24 h showed no differences in levels of Ang II and Ang‐(1‐7) in the SR‐treated group compared to the vehicle (0.1% Tween‐80 in dH2O) group. Interestingly, oral SR treatment in normotensive Sprague‐Dawley control rats (n = 2) modestly increased SBP from a baseline of 120 ± 3 mmHg to 135 ± 2 mmHg after 90 min, suggesting blockade of the known vasodilator actions of the CB1 receptor. After 24 h, SBP recovered to 126 ± 4 mmHg. There was no effect of vehicle on SBP in either strain. These results indicate that CB1 receptor blockade in (mRen2)27 rats may disrupt the hypertension by interfering with the upregulated RAS‐dependent excess SNS activity in these animals, overcoming the blockade of the beneficial ECS effects in the vasculature.Grant Funding Source: Supported by NIH: P01‐HL051952 and R01‐DA03690

Loss of striatal cannabinoid CB1 receptor function in attention‐deficit / hyperactivity disorder mice with point‐mutation of the dopamine transporter

Abnormal dopamine (DA) transmission in the striatum plays a pivotal role in attention-deficit/hyperactivity disorder (ADHD). As striatal DA signalling modulates the endocannabinoid system (ECS), the present study was aimed at investigating cannabinoid CB1 receptor (CB1R) function in a model of ADHD obtained by triple point-mutation in the dopamine transporter (DAT) gene in mice, making them insensitive to cocaine [DAT cocaine-insensitive (DAT-CI) mice]. DAT-CI mice had a marked hyperactive phenotype, and neurophysiological recordings revealed that the sensitivity of CB1Rs controlling GABA-mediated synaptic currents [CB1Rs((GABA)) ] in the striatum was completely lost. In contrast, CB1Rs modulating glutamate transmission [CB1Rs((Glu)) ], and GABA(B) receptors were not affected in this model of ADHD. In DAT-CI mice, the blockade of CB1R((GABA)) function was complete even after cocaine or environmental manipulations activating the endogenous DA-dependent reward system, which are known to sensitize these receptors in control animals. Conversely, the hedonic property of sucrose was intact in DAT-CI mice, indicating normal sweet perception in these animals. Our results point to CB1Rs as novel molecular players in ADHD, and suggest that therapeutic strategies aimed at interfering with the ECS might prove effective in this disorder.

Effects of SR141716A on Cognitive and Depression-Related Behavior in an Animal Model of Premotor Parkinson's Disease

A previous study from our laboratory revealed that moderate nigral dopaminergic degeneration caused emotional and cognitive deficits in rats, paralleling early signs of Parkinson's disease. Recent evidence suggests that the blockade of cannabinoid CB1 receptors might be beneficial to alleviate motor inhibition typical of Parkinson's disease. Here, we investigated whether antagonism of CB1 receptors would improve emotional and cognitive deficits in a rat model of premotor Parkinson's disease. Depression-like behavior and cognition were assessed with the forced swim test and the social recognition test, respectively. Confirming our previous study, rats injected with 6-hydroxydopamine in striatum presented emotional and cognitive alterations which were improved by acute injection of SR141716A. HPLC analysis of monoamine levels demonstrated alterations in the striatum and prefrontal cortex after SR141716A injection. These findings suggest a role for CB1 receptors in the early symptoms caused by degeneration of dopaminergic neurons in the striatum, as observed in Parkinson's disease.

CB1 Receptor Blockade Decreases Ethanol Intake and Associated Neurochemical Changes in Fawn‐Hooded Rats

This study was undertaken to identify the neurochemical changes underlying the attenuation of voluntary ethanol intake induced by the cannabinoid CB1 receptor antagonist AM251 in fawn-hooded rats. Rats were exposed to the 2-bottle-choice paradigm (ethanol 10% v/v or water) for 15 days. After this period, rats received AM251 (3 to 6 mg/kg, i.p.) or vehicle. Voluntary ethanol intake decreased (30%) with the administration of incremental dosages of AM251 (3 mg/kg, 5 days and 6 mg/kg, 5 days) in rats with acquired high preferring ethanol consumption (>3.5 g of ethanol/kg/d). Ethanol intake significantly decreased proopiomelanocortin expression in the arcuate nucleus (38.31%) and micro-opioid-DAMGO-stimulated [(35)S]-GTPgamma binding in the caudate-putamen (40%), nucleus accumbens core (AccC) (32.87%), and shell (AccS) (34.21%). Moreover, ethanol intake increased tyrosine hydroxylase (TH) gene expression in the substantia nigra (24%) and ventral tegmental area (23%) and corticotrophin-releasing gene expression in the paraventricular hypothalamic nucleus (41.6%). The reduction of ethanol intake induced by AM251 was associated with blockade or significant reduction of the changes produced by ethanol in the expression of these genes in key regions related to drug dependence. Interestingly, treatment with AM251 reduced (20%) TH gene expression in rats drinking only water. In this respect, the action of AM251 in reducing TH gene expression may not be specific. Taken together, these results revealed that blockade of cannabinoid CB1 receptors (CB1r) decreased voluntary ethanol intake in ethanol-habituated rats by normalizing the neurochemical alterations induced by ethanol.

The cannabinoid CB1 receptor is involved in the anxiolytic, sedative and amnesic actions of benzodiazepines

Previous studies in our laboratory showed that cannabinoid CB1 receptor knockout mice (CB1-/-) presented increased anxiety-like behaviours that did not respond to the anxiolytic actions of benzodiazepines. These results suggest that the pharmacological effects of benzodiazepines may involve the participation of cannabinoid CB1 receptors. Therefore, the purpose of this study was to examine the effects of alprazolam and the cannabinoid CB1 receptor antagonist AM251 on behavioural assays (light-dark box test, neurological severity score and step-down inhibitory avoidance test) and on the functional activity of the CB1 receptor (WIN-55,212-stimulated [(35)S] guanosine triphosphate (GTP) gamma binding autoradiography).The administration of alprazolam (40 microg/kg, intraperitoneal (i.p.)) decreased anxiety-like behaviours in the light-dark box test and significantly reduced WIN-55,212-stimulated [(35)S]GTPgamma binding autoradiography in the amygdala and in the CA1 field of the hippocampus, but was without effects on CA2, CA3 and the dentate gyrus (DG) of the hippocampus. The administration of AM251 (3 mg/kg, i.p.) blocked the anxiolytic action of alprazolam (40 microg/kg, i.p.), significantly reduced the sedative (ataxia, neurological severity score in the 0.5 cm bar) and the amnesic actions (short time term memory (1 h after electric shock)) of alprazolam (0.5 mg/kg, i.p.).Taken together, these findings revealed that cannabinoid CB1 receptor plays a pivotal role in the pharmacological actions of benzodiazepines. Furthermore, these results suggest that blockade of cannabinoid CB1 receptors may be useful in the treatment of patients with problems related to the consumption of benzodiazepines. Further clinical trials are needed to test this hypothesis.

Blockade of Cannabinoid CB1 Receptors in the central amygdala attenuates morphine reward in rats

Event Abstract Back to Event Blockade of Cannabinoid CB1 Receptors in the central amygdala attenuates morphine reward in rats Maryam Sardari1*, Ameneh Rezayof1 and Mohammad Reza-Zarrindast2 1 University of Tehran, School of Biology, College of Sciences, Iran 2 Tehran Univ. of Medical Science, Dept. of Pharmacology, School of Medicine, Iran Our previous studies suggest that the central amygdala (CeA) may play an important role in morphine reward. Considering the anatomy and functions of the CeA, it may influence the mesocorticolimbic dopaminergic system that mediates morphine reward. On the other hand, it has been shown that cannabinoids produce some pharmacological effects similar to morphine, because there are functional interactions between the cannabinoid and opioid systems. In the present study, the effects of bilateral injections of a selective cannabinoids receptor (CB1) antagonist, AM251 into the CeA on morphine-induced conditioned place preference (CPP) were investigated in male wistar rats. In these experiments, the animals weighting 220-250g at the time of surgery were used. The animals were cannulated in the CeA by stereotaxic instrument, and were allowed to recover 1- week before training. All procedures were carried out in accordance with institutional guide lines for animal care and use. Using a 3-day schedule of conditioning, it was found that the conditioning treatments with subcuntaneous (s.c) injections of different doses of morphine (0-6 mg/kg) induce a conditional place preference (CPP) in a dose-dependent manner. Intra-CeA administration of AM251 (0-120 ng/rat) inhibited the morphine-induced conditioned place preference. Furthermore, intra-CeA administration of AM251 alone did not induce a significant place preference or place aversion. These findings suggest that the cannabinoid CB1 Receptors of the central amygdala are involved in mediating morphine reward. Conference: 41st European Brain and Behaviour Society Meeting, Rhodes Island, Greece, 13 Sep - 18 Sep, 2009. Presentation Type: Poster Presentation Topic: Poster presentations Citation: Sardari M, Rezayof A and Reza-Zarrindast M (2009). Blockade of Cannabinoid CB1 Receptors in the central amygdala attenuates morphine reward in rats. Conference Abstract: 41st European Brain and Behaviour Society Meeting. doi: 10.3389/conf.neuro.08.2009.09.292 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 15 Jun 2009; Published Online: 15 Jun 2009. * Correspondence: Maryam Sardari, University of Tehran, School of Biology, College of Sciences, Tehran, Iran, Jandark96@yahoo.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Maryam Sardari Ameneh Rezayof Mohammad Reza-Zarrindast Google Maryam Sardari Ameneh Rezayof Mohammad Reza-Zarrindast Google Scholar Maryam Sardari Ameneh Rezayof Mohammad Reza-Zarrindast PubMed Maryam Sardari Ameneh Rezayof Mohammad Reza-Zarrindast Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

An endocannabinoid signaling system modulates anxiety-like behavior in male Syrian hamsters

An endocannabinoid signaling system has not been identified in hamsters. We examined the existence of an endocannabinoid signaling system in Syrian hamsters using neuroanatomical, biochemical, and behavioral pharmacological approaches. The distribution of cannabinoid receptors was mapped, and membrane fatty-acid amide hydrolase (FAAH) activity and levels of fatty-acid amides were measured in hamster brain. The impact of cannabinoid CB1 receptor blockade and inhibition of FAAH was evaluated in the elevated plus maze, rota-rod test, and models of unconditioned and conditioned social defeat. A characteristic heterogeneous distribution of cannabinoid receptors was detected in hamster brain using [3H]CP55,940 binding and autoradiography. The FAAH inhibitor URB597 inhibited FAAH activity (IC50 = 12.8 nM) and elevated levels of fatty-acid amides (N-palmitoyl ethanolamine and N-oleoyl ethanolamine) in hamster brain. Anandamide levels were not reliably altered. The cannabinoid agonist WIN55,212-2 (1- 10 mg/kg i.p.) induced CB1-mediated motor ataxia. Blockade of CB1 with rimonabant (5 mg/kg i.p.) induced anxiogenic-like behavior in the elevated plus maze. URB597 (0.1-0.3 mg/kg i.p.) induced CB1-mediated anxiolytic-like effects in the elevated plus maze, similar to the benzodiazepine diazepam (2 mg/kg i.p.). Diazepam (2-6 mg/kg i.p.) suppressed the expression, but not the acquisition, of conditioned defeat. By contrast, neither URB597 (0.3-3.0 mg/kg i.p.) nor rimonabant (5 mg/kg i.p.) altered unconditioned or conditioned social defeat or rota-rod performance. Endocannabinoids engage functional CB1 receptors in hamster brain to suppress anxiety-like behavior and undergo enzymatic hydrolysis catalyzed by FAAH. Our results further suggest that neither unconditioned nor conditioned social defeat in the Syrian hamster is dependent upon cannabinoid CB1 receptor activation.

A Human Fatty Acid Amide Hydrolase (FAAH) Functional Gene Variant Is Associated With Lower Blood Pressure in Young Males

Fatty acid amide hydrolase (FAAH) inhibitors, preventing endocannabinoid (EC) degradation, reduce blood pressure (BP) and heart rate in young male (YM) hypertensive rodents. The functional human FAAH 129T gene variant results in reduced protein level and enzymatic activity but its relationship with BP is unknown. This study investigates the relationship among FAAH P129T alleles and cardiovascular features in YMs at baseline and after 9-year follow-up, and in older male obese hypertensive (OH) patients, in whom the EC system (ECS) is overactive. Genotype analysis was performed in 215 Caucasian male students (24 (0.2) years old) and in 185 older OH patients (50 (0.2) years old). YMs were also followed up for 9 years. Clinical and anthropometric variables, BP, cardiac and carotid artery echographic measurements were evaluated. YMs with the FAAH 129T allele had lower systolic (P = 0.042) and mean BP (P = 0.022), and a trend toward lower diastolic BP (P = 0.06). Such significant association was maintained at follow-up. In contrast, the same allele was not associated with BP in older OH. No association was found with other cardiac and vascular variables. An FAAH defective gene variant results in lower BP in YMs, similar to the findings in young rodents. This effect is lost in older OH patients. Because cannabinoid CB1 receptor blockade is associated with BP reduction in OH patients, EC effects and the use of ECS-interfering drugs is likely to be age and clinical-condition dependent.

Enhanced striatal glutamate release after the administration of rimonabant to 6-hydroxydopamine-lesioned rats

While recent studies have shown that the blockade of cannabinoid CB(1) receptors might be beneficial to alleviate the motor inhibition typical of Parkinson's disease (PD), the neurochemical substrates for this effect remain elusive. Here we have carried out microdialysis experiments to determine whether the effects of rimonabant, a selective antagonist of CB(1) receptors, might be associated with changes in striatal glutamate release in a rat model of PD generated by intracerebroventricular injection of 6-hydroxydopamine. Our data demonstrate that the treatment with rimonabant slightly increased striatal glutamate release in control rats, although this effect was only evident with the highest dose of rimonabant tested (1mg/kg). However, the increase in glutamate release was much more marked in the parkinsonian rats where similar changes were observed at a dose of 1 and 0.1mg/kg, exactly the same dose that relieved motor inhibition in previous behavioral studies. In summary, the potential of rimonabant to act as a possible antihypokinetic agent in parkinsonian rats seems to be related to enhanced glutamate release from excitatory afferents to the striatum. This observation is of potential clinical interest, particularly for those parkinsonian patients that exhibit a poor response to classic levodopa treatment.

Paracrine Activation of Hepatic CB 1 Receptors by Stellate Cell-Derived Endocannabinoids Mediates Alcoholic Fatty Liver

Alcohol-induced fatty liver, a major cause of morbidity, has been attributed to enhanced hepatic lipogenesis and decreased fat clearance of unknown mechanism. Here we report that the steatosis induced in mice by a low-fat, liquid ethanol diet is attenuated by concurrent blockade of cannabinoid CB1 receptors. Global or hepatocyte-specific CB1 knockout mice are resistant to ethanol-induced steatosis and increases in lipogenic gene expression and have increased carnitine palmitoyltransferase 1 activity, which, unlike in controls, is not reduced by ethanol treatment. Ethanol feeding increases the hepatic expression of CB1 receptors and upregulates the endocannabinoid 2-arachidonoylglycerol (2-AG) and its biosynthetic enzyme diacylglycerol lipase beta selectively in hepatic stellate cells. In control but not CB1 receptor-deficient hepatocytes, coculture with stellate cells from ethanol-fed mice results in upregulation of CB1 receptors and lipogenic gene expression. We conclude that paracrine activation of hepatic CB1 receptors by stellate cell-derived 2-AG mediates ethanol-induced steatosis through increasing lipogenesis and decreasing fatty acid oxidation.

Blockade of cannabinoid CB1 receptors improves renal function, metabolic profile, and increased survival of obese Zucker rats

Obesity is a major risk factor in the development of chronic renal failure. Rimonabant, a cannabinoid CB1 receptor antagonist, improves body weight and metabolic disorders; however, its effect on mortality and chronic renal failure associated with obesity is unknown. Obese Zucker rats received either rimonabant or vehicle for 12 months and were compared to a pair-fed but untreated group of obese rats. Mortality in the obese rats was significantly reduced by rimonabant along with a sustained decrease in body weight, transient reduction in food intake, and an increase in plasma adiponectin. This was associated with significant reduction in plasma total cholesterol, low-density lipoprotein cholesterol/high-density lipoprotein cholesterol ratio, triglycerides, glucose, norepinephrine, plasminogen activator inhibitor 1, and preservation of pancreatic weight and beta-cell mass index. The cannabinoid antagonist attenuated the increase in proteinuria, urinary N-acetylglucosaminidase excretion, plasma creatinine, and urea nitrogen levels while improving creatinine clearance. Renal hypertrophy along with glomerular and tubulointerstitial lesions were reduced by rimonabant. Although the drug did not modify hemodynamics, it normalized the pressor response to angiotensin II. Our study suggests that in a rat model of chronic renal failure due to obesity, rimonabant preserves renal function and increases survival.

Pretreatment with subeffective doses of Rimonabant attenuates orexigenic actions of orexin A-hypocretin 1

Recent studies suggest that blockade of cannabinoid CB1 receptors suppresses feeding, an effect observed in humans treated with the cannabinoid CB1 antagonist Rimonabant. A cross-talk between cannabinoids and other systems controlling appetite might exist since cannabinoid receptors are present in hypothalamic neural circuits involved in feeding regulation and energy expenditure. Orexin A-hypocretin 1, an orexigenic peptide, is an ideal candidate to interact with cannabinoid receptors. Both of them play an important role in feeding and they co-localize in similar brain regions. To study this hypothesis we investigated (a) the effects on food intake of either orexin A-hypocretin 1 or the cannabinoid CB1 receptor antagonist Rimonabant in pre-fed rats, and (b) the interaction between them by monitoring the effects of the combined administration of cannabinoids and orexin A-hypocretin 1 in pre-fed rats. The results show that (1) orexin A-hypocretin 1 is a short-term modulator of appetite that increases food intake in pre-fed rats, (2) Rimonabant decreases food intake and (3) such effective and subeffective doses of Rimonabant block the orexigenic effect of orexin A-hypocretin 1. The results support the idea that cannabinoid and orexin A-hypocretin 1 systems share a common mechanism in food intake and indicate that the hypothalamic orexigenic circuits are involved in cannabinoid CB1 receptor antagonism-mediated reduction of appetite.

Cannabinoid CB1Receptor Antagonist AM251 Inhibits Cocaine-Primed Relapse in Rats: Role of Glutamate in the Nucleus Accumbens

Blockade of cannabinoid CB1 receptors has been reported to inhibit cocaine- or cocaine cue-induced reinstatement of drug seeking. However, the mechanisms underlying this action are poorly understood. Given the importance of dopamine, glutamate, and GABA in cocaine reward and relapse, we studied the effects of AM251 [N-(piperidin-1-yl)-5-(4-iodophonyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide], a novel highly selective CB1 receptor antagonist, on cocaine-primed reinstatement of drug-seeking behavior and on cocaine-induced changes in extracellular DA, glutamate, and GABA in the nucleus accumbens (NAc) under reinstatement conditions. We found that systemic administration of AM251 selectively inhibited cocaine-induced, but not sucrose plus sucrose cue-induced, reinstatement of reward-seeking behavior. AM251 alone did not trigger reinstatement. Local perfusion of AM251 into the NAc or the dorsal striatum also inhibited cocaine-triggered reinstatement. AM251 alone dose dependently elevated NAc glutamate in a voltage-dependent Na+ channel-dependent manner. AM251 did not affect NAc DA or GABA. Pretreatment with AM251 dose dependently inhibited cocaine-induced increases in NAc glutamate but not in DA. Blockade of NAc metabotropic glutamate mGluR2/3 receptors by LY341495 [(2S)-2-amino-2-[(1S,2S)-2-carboxycycloprop-1-yl]-3-(xanth-9-yl) propanoic acid] slightly facilitated cocaine-enhanced glutamate release but blocked the antagonism of cocaine-induced reinstatement by AM251. These data suggest the following: (1) CB1 receptors exert tonic inhibition over NAc glutamate release under cocaine-extinction conditions; (2) blockade of CB1 receptors by AM251 inhibits cocaine-enhanced NAc glutamate release and cocaine-triggered reinstatement; and (3) these effects appear to be mediated by activation of presynaptic mGluR2/3 autoreceptors secondary to AM251-induced increase (disinhibition) of NAc glutamate release.

Regulation, Function, and Dysregulation of Endocannabinoids in Models of Adipose and β-Pancreatic Cells and in Obesity and Hyperglycemia

Cannabinoid CB(1) receptor blockade decreases weight and hyperinsulinemia in obese animals and humans in a way greatly independent from food intake. The objective of this study was to investigate the regulation and function of the endocannabinoid system in adipocytes and pancreatic beta-cells. Mouse 3T3-F442A adipocytes and rat insulinoma RIN-m5F beta-cells, pancreas and fat from mice with diet-induced obesity, visceral and sc fat from patients with body mass index equal to or greater than 30 kg/m(2), and serum from normoglycemic and type 2 diabetes patients were studied. Endocannabinoid enzyme and adipocyte protein expression, and endocannabinoid and insulin levels were measured. Endocannabinoids are present in adipocytes with levels peaking before differentiation, and in RIN-m5F beta-cells, where they are under the negative control of insulin. Chronic treatment of adipocytes with insulin is accompanied by permanently elevated endocannabinoid signaling, whereas culturing of RIN-m5F beta-cells in high glucose transforms insulin down-regulation of endocannabinoid levels into up-regulation. Epididymal fat and pancreas from mice with diet-induced obesity contain higher endocannabinoid levels than lean mice. Patients with obesity or hyperglycemia caused by type 2 diabetes exhibit higher concentrations of endocannabinoids in visceral fat or serum, respectively, than the corresponding controls. CB(1) receptor stimulation increases lipid droplets and decreases adiponectin expression in adipocytes, and it increases intracellular calcium and insulin release in RIN-m5F beta-cells kept in high glucose. Peripheral endocannabinoid overactivity might explain why CB(1) blockers cause weight-loss independent reduction of lipogenesis, of hypoadiponectinemia, and of hyperinsulinemia in obese animals and humans.