Cannabinoid Receptor Antagonist SR141716A Research Articles

Functional consequences of short-term exposure to opioids versus cannabinoids in nonhuman primates

Opioids provide pain relief but are associated with several adverse effects. Researchers are exploring cannabis-based medicine as an alternative. However, little is known about the tendency for physical dependence on cannabinoids in comparison with that on opioids in primates. The aim of this study was to compare the potency of heroin and delta-9-tetrahydrocannabinol (THC) in eliciting analgesic effects and the development of physical dependence between opioids and cannabinoids in both male and female rhesus monkeys. Systemic administration of either heroin (0.03–0.18 mg/kg) or THC (0.3–1.8 mg/kg) in a dose-dependent manner produced antinociceptive effects against an acute thermal nociceptive stimulus. The μ-opioid receptor antagonist naltrexone (0.01 mg/kg) and the cannabinoid receptor antagonist SR141716A (0.3 mg/kg) produced the same degree of rightward shift in the dose-response curves for heroin- and THC-induced antinociception, respectively. Monkeys implanted with telemetry devices were subjected to short-term repeated administrations (two injections per day for 1–3 days) of either heroin (0.18 mg/kg), morphine (1.8 mg/kg), THC (1.8 mg/kg), or CP 55,940 (0.032 mg/kg). Administration of naltrexone (0.01 mg/kg) increased respiration, heart rate, and blood pressure in heroin- or morphine-treated monkeys. In contrast, administration of SR141716A (0.3 mg/kg) did not cause a significant change in these physiological parameters in THC- or CP 55,940-treated monkeys. Additionally, morphine, but not CP 55,940, enhanced the monkeys’ hypersensitivity to the algogen capsaicin. Collectively, these results demonstrate that in nonhuman primates, both opioids and cannabinoids exert comparable antinociception; however, physical dependence on opioids, but not cannabinoids, at their antinociceptive doses, occurs following short-term exposures.

Peripherally Selective CB1 Receptor Antagonist Improves Symptoms of Metabolic Syndrome in Mice.

Metabolic syndrome (MetS) is a complex disorder that stems from the additive effects of multiple underlying causes such as obesity, insulin resistance, and chronic low-grade inflammation. The endocannabinoid system plays a central role in appetite regulation, energy balance, lipid metabolism, insulin sensitivity, and β-cell function. The type 1 cannabinoid receptor (CB1R) antagonist SR141716A (rimonabant) showed promising antiobesity effects, but its use was discontinued due to adverse psychiatric events in some users. These adverse effects are due to antagonism of CB1R in the central nervous system (CNS). As such, CNS-sparing CB1R antagonists are presently being developed for various indications. In this study, we report that a recently described compound, 3-{1-[8-(2-chlorophenyl)-9-(4-chlorophenyl)-9H-purin-6-yl]piperidin-4-yl}-1-[6-(difluoromethoxy)pyridin-3-yl]urea (RTI1092769), a pyrazole based weak inverse agonist/antagonist of CB1 with very limited brain exposure, improves MetS related complications. Treatment with RTI1092769 inhibited weight gain and improved glucose utilization in obese mice maintained on a high fat diet. Hepatic triglyceride content and steatosis significantly improved with treatment. These phenotypes were supported by improvement in several biomarkers associated with nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH). These results reinforce the idea that CB1 antagonists with limited brain exposure should be pursued for MetS and other important indications.

CB1 ligands modulate learning and memory of OBX rats

Purpose. The brain endocannabinoid system has been shown to play a role in learning and memory processes, although the exact mechanisms by which it interferes in these processes are not well established. We aimed at studying the effects of CB1 receptor ligands on learning and memory of rats with an experimental model of depression - olfactory bulbectomy (OBX). Material and methods. Cannabinoid CB1 receptor agonist HU-210 (5 µg) and cannabinoid CB1 receptor antagonist SR 141716A (3 µg) were microinjected i.c.v. in male Wistar rats with olfactory bulbectomy (OBX) model of depression. A passive avoidance task (step through) was used as a test for learning and memory. Results. In the non-OBX group, HU-210 impaired learning and memory processes expressed by the shortened latency time on the retention tests (3 hours and 24 hours after training) and by the decreased percentage of rats that have reached the learning criterion, as compared to the saline-treated controls. SR 141716A did not affect significantly the performance of rats in the step-through task. In the OBX rats HU-210 prolonged the latency time as compared to the saline-treated OBX controls, while SR 141716A did not affect significantly the OBX-related learning and memory deficits. Conclusion. These findings suggest complex modulatory effect of CB1 receptor agonist on learning and memory processes in non-OBX and OBX rats.

Microstructural analysis of rat ethanol and water drinking patterns using a modified operant self-administration model

BackgroundEthanol drinking pattern has emerged as an important factor in the development, maintenance, and health consequences of alcohol use disorders in humans. The goal of these studies was to further our understanding of this important factor through refinement of an operant rodent model of ethanol consumption capable of drinking pattern microstructural analysis. We evaluated measures of total consumption, appetitive behavior, and drinking microstructure for ethanol and water at baseline and assessed alterations induced by two treatments previously shown to significantly alter gross ethanol appetitive and consummatory behaviors in opposing directions. MethodsMale Long–Evans rats were trained on an FR1 operant paradigm which allowed for continuous liquid access until an 8second pause in consumption resulted in termination of liquid access. Total appetitive and consummatory behaviors were assessed in addition to microstructural drinking pattern for both ethanol and water during a five day baseline drinking period, after chronic intermittent ethanol vapor exposure, and following administration of a cannabinoid receptor antagonist SR141716a. ResultsAs in previous operant studies, ethanol vapor exposure resulted in increases in ethanol-directed responding, total consumption, and rate of intake. Further, striking differential alterations to ethanol and water bout size, duration, and lick pattern occurred consistent with alterations in hedonic evaluation. Vapor additionally specifically reduced the number of ethanol-directed lever presses which did not result in subsequent consumption. SR141716a administration reversed many of these effects. ConclusionsThe addition of microstructural analysis to operant self-administration by rodents provides a powerful and translational tool for the detection of specific alterations in ethanol drinking pattern which may enable insights into neural mechanisms underlying specific components of drug consumption.

Distinct roles of the endocannabinoids anandamide and 2-arachidonoylglycerol in social behavior and emotionality at different developmental ages in rats

To date, our understanding of the relative contribution and potential overlapping roles of the endocannabinoids anandamide (AEA) and 2-arachidonoylglycerol (2-AG) in the regulation of brain function and behavior is still limited. To address this issue, we investigated the effects of systemic administration of JZL195, that simultaneously increases AEA and 2-AG signaling by inhibiting their hydrolysis, in the regulation of socio-emotional behavior in adolescent and adult rats.JZL195, administered at the dose of 0.01mg/kg, increased social play behavior, that is the most characteristic social activity displayed by adolescent rats, and increased social interaction in adult animals. At both ages, these behavioral effects were antagonized by the CB1 cannabinoid receptor antagonist SR141716A and were associated with increased brain levels of 2-AG, but not AEA. Conversely, at the dose of 1mg/kg, JZL195 decreased general social exploration in adolescent rats without affecting social play behavior, and induced anxiogenic-like effects in the elevated plus-maze test both in adolescent and adult animals. These effects, mediated by activation of CB1 cannabinoid receptors, were paralleled by simultaneous increase in AEA and 2-AG levels in adolescent rats, and by an increase of only 2-AG levels in adult animals.These findings provide the first evidence for a role of 2-AG in social behavior, highlight the different contributions of AEA and 2-AG in the modulation of emotionality at different developmental ages and suggest that pharmacological inhibition of AEA and 2-AG hydrolysis is a useful approach to investigate the role of these endocannabinoids in neurobehavioral processes.

Δ9-tetrahydrocannabinol prevents methamphetamine-induced neurotoxicity.

Methamphetamine (METH) is a potent psychostimulant with neurotoxic properties. Heavy use increases the activation of neuronal nitric oxide synthase (nNOS), production of peroxynitrites, microglia stimulation, and induces hyperthermia and anorectic effects. Most METH recreational users also consume cannabis. Preclinical studies have shown that natural (Δ9-tetrahydrocannabinol, Δ9-THC) and synthetic cannabinoid CB1 and CB2 receptor agonists exert neuroprotective effects on different models of cerebral damage. Here, we investigated the neuroprotective effect of Δ9-THC on METH-induced neurotoxicity by examining its ability to reduce astrocyte activation and nNOS overexpression in selected brain areas. Rats exposed to a METH neurotoxic regimen (4×10 mg/kg, 2 hours apart) were pre- or post-treated with Δ9-THC (1 or 3 mg/kg) and sacrificed 3 days after the last METH administration. Semi-quantitative immunohistochemistry was performed using antibodies against nNOS and Glial Fibrillary Acidic Protein (GFAP). Results showed that, as compared to corresponding controls (i) METH-induced nNOS overexpression in the caudate-putamen (CPu) was significantly attenuated by pre- and post-treatment with both doses of Δ9-THC (−19% and −28% for 1 mg/kg pre- and post-treated animals; −25% and −21% for 3 mg/kg pre- and post-treated animals); (ii) METH-induced GFAP-immunoreactivity (IR) was significantly reduced in the CPu by post-treatment with 1 mg/kg Δ9-THC1 (−50%) and by pre-treatment with 3 mg/kg Δ9-THC (−53%); (iii) METH-induced GFAP-IR was significantly decreased in the prefrontal cortex (PFC) by pre- and post-treatment with both doses of Δ9-THC (−34% and −47% for 1 mg/kg pre- and post-treated animals; −37% and −29% for 3 mg/kg pre- and post-treated animals). The cannabinoid CB1 receptor antagonist SR141716A attenuated METH-induced nNOS overexpression in the CPu, but failed to counteract the Δ9-THC-mediated reduction of METH-induced GFAP-IR both in the PFC and CPu. Our results indicate that Δ9-THC reduces METH-induced brain damage via inhibition of nNOS expression and astrocyte activation through CB1-dependent and independent mechanisms, respectively.

Effects of Acutely Applied Cannabinoid CB1 Ligands on Nociception in Rats with a Model of Depression

The effects of CB1 receptor agonist HU-210 and cannabinoid CB1 receptor antagonist SR 141716A on nociception of male Wistar rats with a model of depression (bilateral olfactory bulbectomy, OBX) were studied. HU-210 (5 g) and SR 141716A (3 g) were acutely microinjected i.c.v. on the developed depression background. Nociception was examined as applied mechanical pressure on the left hind paw of the rat (analgesy-meter test, Randall & Sellitto). In the OBX rats, it was found that the pain threshold was increased. HU-210 significantly increased the pain threshold in OBX rats, i.e. decreased the pain sensitivity as compared to saline-treated OBX controls and to sham-operated controls, suggesting an implication of CB1 receptors in nociception of OBX rats. SR 141716A did not affect the nociception in OBX rats. These results suggest that stimulation of CB1 receptors in rats with a model of depression exerted antinociceptive effect.

On the Role of Cannabinoid CB1- and μ-Opioid Receptors in Motor Impulsivity

Previous studies using a rat 5-choice serial reaction time task have established a critical role for dopamine D2 receptors in regulating increments in motor impulsivity induced by acute administration of the psychostimulant drugs amphetamine and nicotine. Here we investigated whether cannabinoid CB1 and/or μ-opioid receptors are involved in nicotine-induced impulsivity, given recent findings indicating that both receptor systems mediate amphetamine-induced motor impulsivity. Results showed that the cannabinoid CB1 receptor antagonist SR141716A, but not the opioid receptor antagonist naloxone, reduced nicotine-induced premature responding, indicating that nicotine-induced motor impulsivity is cannabinoid, but not opioid receptor-dependent. In contrast, SR141716A did not affect impulsivity following a challenge with the dopamine transporter inhibitor GBR 12909, a form of drug-induced impulsivity that was previously found to be dependent on μ-opioid receptor activation. Together, these data are consistent with the idea that the endogenous cannabinoid, dopamine, and opioid systems each play important, but distinct roles in regulating (drug-induced) motor impulsivity. The rather complex interplay between these neurotransmitter systems modulating impulsivity will be discussed in terms of the differential involvement of mesocortical and mesolimbic neurocircuitry.

Revisiting the complex influences of cannabinoids on motor functions unravels pharmacodynamic differences between cannabinoid agonists

While numerous cannabinoid ligands were historically characterized using the tetrad test (hypomobility, catalepsy, hypothermia, analgesia), only few studies have extensively compared HU 210 and CP 55,940 which are nowadays classically used as reference agonists. Therefore, we herein re-examined the acute and the sustained changes in motor activities mediated by these two agonists in adult rats. As expected for cannabinoid agonists, exposure to either HU 210 or CP 55,940 induced a marked reduction in spontaneous locomotion. This reduction observed as early as 15 min after injection was correlated with the typical rearing and cataleptic responses, and was reversed by co-administration of the CB 1 cannabinoid receptor antagonist SR 141716A. Nevertheless, HU 210, but not CP 55,940, was found to induce persistent responses, lasting for at least 24 h. Also suggesting the involvement of additional targets for HU 210, 10 mg/kg SR 141716A failed to reverse the persistent HU 210-mediated decline in locomotion and rearing, while 1 mg/kg was sufficient to completely abolish the behavioural responses measured 6 h after the injection. Beside pharmacokinetic differences, these data therefore denote distinct pharmacodynamic profiles for HU 210 and CP 55,940. Together, these results suggest that HU 210 displays multicomponent responses that should be taken into account when interpreting data from in vivo/ex vivo studies.

Prosocial Effects of Nicotine and Ethanol in Adolescent Rats Through Partially Dissociable Neurobehavioral Mechanisms

The widespread use of tobacco and alcohol among adolescents might be related to the ability of nicotine and ethanol to facilitate social interactions. To investigate the neurobehavioral mechanisms underlying the prosocial effects of nicotine and ethanol, we focused on social play behavior, the most characteristic social activity in adolescent rats. Social play behavior is rewarding, and it is modulated through opioid, cannabinoid and dopaminergic neurotransmission, which are also involved in the reinforcing properties of nicotine and ethanol. We found that nicotine and ethanol increased social play, without affecting locomotion or social exploration. Their effects depended on the level of social activity of the partner, and were comparable in familiar and unfamiliar environments. At doses that increased social play, nicotine and ethanol had no anxiolytic effects in the elevated plus-maze. By contrast, the prototypical anxiolytic drug diazepam reduced social play at doses that reduced anxiety. The effects of nicotine on social play were blocked by the opioid receptor antagonist naloxone, the CB1 cannabinoid receptor antagonist SR141716A, and the dopamine receptor antagonist alpha-flupenthixol. The effects of ethanol were blocked by SR141716A and alpha-flupenthixol, but not by naloxone. Combined administration of subeffective doses of nicotine and ethanol only modestly enhanced social play. These results show that the facilitatory effects of nicotine and ethanol on social play are behaviorally specific and mediated through neurotransmitter systems involved in positive emotions and motivation, through partially dissociable mechanisms. Furthermore, the stimulating effects of nicotine and ethanol on social play behavior are independent of their anxiolytic-like properties.

Interactions between cannabinoids and alcohol

Event Abstract Back to Event Interactions between cannabinoids and alcohol Fernando Rodriguez-de-Fonseca1* 1 Hospital Carlos Haya, Avenida Carlos Haya 82, Laboratorio de Medicina Regenerativa, Fundación IMABIS, Spain The endogenous cannabinoid anandamide participates in the neuroadaptations associated with chronic ethanol exposure and serves as a link between exogenous cannabinoid administration and alcohol actions. While cannabinoid exposure favors alcohol intake, cannabinoid CB1 receptor antagonist reduces both alcohol intake and cue-induced relapse to alcohol selfadministration. Thus, intraperitoneal administration of the cannabinoid CB1 receptor antagonist SR141716A (0.03, 1.0 and 3.0 mg/kg) markedly inhibits ethanol selfadministration and conditioned reinstatement of ethanol-seeking behavior in both Wistar and Marchegian-Sardinian Alcohol preferring rats (mSp). ED50 analysis showed significantly higher sensitivity (p<0.05) to the effect of SR141716A in msP rats compared to heterogeneous Wistar rats. On the other side, acute peripheral administration of ethanol (4 gr/kg, i.p.) decreased anandamide in the cerebellum, the hippocampus and the ventral striatum, as well as in plasma and adipose tissue. Parallel decreases of a second acylethanolamide, palmithylethanolamide were observed in the brain. Effects were observed 45-90 min after ethanol administration. In vivo studies revealed that anandamide decreases were associated with a remarkable inhibition of the release of both anadamide and glutamate release in the ventral striatum. There were no changes in the expression and enzimatic activity of the main enzyme that degradates anandamide, the fatty acid amidohydrolase. Acute ethanol did not change neither the activity of n-acyltransferase, the enzyme that catalyzes the synthesis of the anandamide precursor, nor the expression of NAPE-PLD, the enzyme that releases anandamide from membrane phospholipid precursors. These results suggest that receptor-mediated release of acylethanolamide is inhibited by the acute administration of ethanol, and that this effect is not derived of increased fatty acid ethanolamide degradation. In conclusion, we provide clear evidence that the endogenous cannabinoid system participates in alcohol-seeking behavior in rats, and that alcohol directly modulates endocannabinoid production. Conference: 3rd Mediterranean Conference of Neuroscience , Alexandria, Egypt, 13 Dec - 16 Dec, 2009. Presentation Type: Oral Presentation Topic: Symposium 02 – Cannabinoids and brain reward processes Citation: Rodriguez-de-Fonseca F (2009). Interactions between cannabinoids and alcohol. Front. Neurosci. Conference Abstract: 3rd Mediterranean Conference of Neuroscience . doi: 10.3389/conf.neuro.01.2009.16.009 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: 18 Nov 2009; Published Online: 18 Nov 2009. * Correspondence: Fernando Rodriguez-de-Fonseca, Hospital Carlos Haya, Avenida Carlos Haya 82, Laboratorio de Medicina Regenerativa, Fundación IMABIS, 13331 Marseille, Spain, fernando.rodriguez@ibima.eu 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 Fernando Rodriguez-de-Fonseca Google Fernando Rodriguez-de-Fonseca Google Scholar Fernando Rodriguez-de-Fonseca PubMed Fernando Rodriguez-de-Fonseca 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.

Divergent Effects of Anandamide Transporter Inhibitors with Different Target Selectivity on Social Play Behavior in Adolescent Rats

The endocannabinoid system plays an important role in the modulation of affect, motivation, and emotion. Social play behavior is a natural reinforcer in adolescent rats, and we have recently shown that interacting endocannabinoid, opioid, and dopamine systems modulate social play. In the present study, we tested the hypothesis that, in contrast to administration of exogenous cannabinoid agonists, increasing local endocannabinoid signaling through anandamide transporter inhibition enhances social play. To this aim, we tested the effects of two anandamide transporter inhibitors with different target selectivity on social play behavior in adolescent rats. Interestingly, we found that the prototypical anandamide transporter inhibitor N-(4-hydroxyphenyl)-arachidonamide (AM404) reduced social play, whereas its more selective analog N-arachidonoyl-(2-methyl-4-hydroxyphenyl)amine (VDM11) enhanced it. The effects of AM404 were not mediated through its known pharmacological targets, since they were not blocked by the CB(1) cannabinoid receptor antagonist N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide hydrochloride (SR141716A), the CB(2) cannabinoid receptor antagonist N-(1,3,3-trimethylbicyclo(2.2.1)heptan-2-yl)-5-(4-chloro-3-methylphenyl)-1-(4-methylbenzyl)pyrazole-3-carboxamide (SR144528), or by the transient receptor potential vanilloid 1 receptor antagonist capsazepine. In contrast, the increase in social play induced by VDM11 was dependent on cannabinoid, opioid, and dopaminergic neurotransmission, since it was blocked by the CB(1) cannabinoid receptor antagonist SR141716A, the opioid receptor antagonist naloxone, and the dopamine receptor antagonist alpha-flupenthixol. These findings support the notion that anandamide plays an important role in the modulation of social interaction in adolescent rats, and they suggest that selective anandamide transporter inhibitors might be useful for the treatment of social dysfunctions. Furthermore, these results suggest that off-target effects may be responsible for some of the conflicting effects of anandamide transporter inhibitors on behavior.

Auditory gating in rat hippocampus and medial prefrontal cortex: Effect of the cannabinoid agonist WIN55,212-2

Sensory gating can be assessed in rodents and humans using an auditory conditioning (C)–test (T) paradigm, with schizophrenic patients exhibiting a loss of gating. Dysregulation of the endocannabinoid system has been proposed to be involved in the pathogenesis of schizophrenia. We studied auditory gating and the effects of the cannabinoid agonist WIN55,212-22 on gating in CA3 and dentate gyrus (DG) of the hippocampus and medial prefrontal cortex (mPFC) in male Lister hooded rats using in vivo electrophysiology. The effects of a single dose of WIN55,212-2 on the N2 local field potential (LFP) test/conditioning amplitude ratios (T/C ratio) and response latencies were examined. In rats that demonstrated gating of N2, mPFC showed higher T/C ratios and shorter conditioning response latencies compared to DG and CA3. WIN55,212-2 disrupted auditory gating in all three areas with a significant increase in test amplitudes in the gating rats. A group of non-gating rats demonstrated higher test amplitudes and higher T/C ratios compared to gating rats. WIN55,212-2 had no effect on T/C ratios in the non-gating rats. The cannabinoid receptor (CB1) antagonist SR141716A prevented WIN55,212-2 induced disruption of gating. This study demonstrates gated auditory-evoked responses in CA3, DG and mPFC. The mPFC showed an early phase of gating which may later be modulated by CA3 and DG activity. Furthermore, cannabinoid receptor activation disrupted auditory gating in CA3, DG and mPFC, an effect which was prevented by CB1 receptor antagonism. The results further demonstrate the presence of a non-gating rat population which responded differently to cannabinoid agonists.

Role of metabotropic glutamate receptor 5 in the procholinergic effects of neuropsychotherapeutic compounds

We investigated the participation of the metabotropic glutamate receptor type 5 (mGluR5) in mediating increases in cortical acetylcholine (ACh) efflux elicited by established or putative neuropsychotherapeutic compounds, using in vivo microdialysis in rats. The norepinephrine transporter inhibitor atomoxetine, the cannabinoid CB1 receptor antagonist SR141716A, the dopamine D1 receptor agonist dihydrexidine, and the atypical antipsychotic clozapine increased cortical ACh (by about 2-3 fold), whereas the mGluR5 antagonist 2-methyl-6-(phenylethynyl)-pyridine (MPEP) by itself had no effect. The stimulatory effects of atomoxetine, SR141716A and dihydrexidine on cortical ACh were abolished by pretreatment with MPEP. MPEP also attenuated the stimulatory effect of clozapine on ACh efflux. Thus, mGluR5 activation appears to be involved in the procholinergic effects of compounds that exhibit therapeutic properties or potential in neuropsychiatry.

Endogenous cannabinoid anandamide inhibits nicotinic acetylcholine receptor function in mouse thalamic synaptosomes

The effects of the endogenous cannabinoid anandamide [arachidonylethanolamide (AEA)] on the function of nicotinic acetylcholine receptor (nAChR) were investigated using the 86Rb+ efflux assay in thalamic synaptosomes. AEA reversibly inhibited 86Rb+ efflux induced by 300 microM ACh with an IC50 value of 0.9 +/- 2 microM. Pre-treatment with the cannabinoid (CB1) receptor antagonist SR141716A (1 microM), the CB2 receptor antagonist SR144528 (1 microM), or pertussis toxin (0.2 mg/mL) did not alter the inhibitory effects of AEA, suggesting that known CB receptors are not involved in AEA inhibition of nAChRs. AEA inhibition of 86Rb+ efflux was not reversed by increasing acetylcholine (ACh) concentrations. In radioligand binding studies, the specific binding of [3H]-nicotine was not altered in the presence of AEA, indicating that AEA inhibits the function of nAChR in a non-competitive manner. Neither the amidohydrolase inhibitor phenylmethylsulfonyl fluoride (0.2 mM) nor the cyclooxygenase inhibitor, indomethacin, (5 microM) affected AEA inhibition of nAChRs, suggesting that the effect of AEA is not mediated by its metabolic products. Importantly, the extent of AEA inhibition of 86Rb+ efflux was significantly attenuated by the absence of 1% fatty acid free bovine serum albumin pre-treatment, supporting previous findings that fatty acid-like compounds modulate the activity of nAChRs. Collectively, the results indicate that AEA inhibits the function of nAChRs in thalamic synaptosomes via a CB-independent mechanism and that the background activity of these receptors is affected by fatty acids and AEA.

Bidirectional cannabinoid modulation of social behavior in adolescent rats

Marijuana use in adolescents is a highly social activity, and interacting endocannabinoid and opioid systems may modulate social reward. However, cannabinoid exposure has been reported to reduce social behavior. The aim of this study was to elucidate the mechanisms underlying the paradoxical relationship between cannabinoid exposure and sociability. We investigated the effect of cannabinoid agonists with a different mechanism of action on social play behavior in adolescent rats. In addition, we examined whether endocannabinoid neurotransmission interacts with opioid and dopaminergic neurotransmission in the modulation of social play behavior. The direct CB1 cannabinoid receptor agonist WIN55,212-2 reduced social play. However, the indirect cannabinoid agonist URB597, which inhibits the hydrolysis of the endocannabinoid anandamide, enhanced social play. This effect of URB597 depended upon stimulation of opioid and dopamine receptors. The well-known stimulatory effect of morphine on social play was attenuated by the CB1 cannabinoid receptor antagonist SR141716A, but independent of dopamine receptor stimulation. Combined treatment with ineffective doses of URB597 and morphine increased social play. Cannabinoid neurotransmission can both enhance and inhibit social interaction in adolescent rats depending on how the endocannabinoid system is stimulated. Activation of cannabinoid receptors throughout the brain, which occurs during cannabis use, inhibits sociability. In contrast, on-demand release of endocannabinoids facilitates social interaction, which is magnified by indirect cannabinoid agonists through an interaction with opioid and dopaminergic neurotransmission. These results shed light on the paradoxical relationship between cannabis exposure and sociability and suggest that endocannabinoid degradation inhibitors hold promise for the treatment of social dysfunctions.

Analogs of SR-141716A (Rimonabant) alter d-amphetamine-evoked [ 3H] dopamine overflow from preloaded striatal slices and amphetamine-induced hyperactivity

The CB 1 cannabinoid receptor antagonist SR-141716A (Rimonabant) markedly diminishes the behavioral effects of opiates and nicotine and has been an important tool to ascertain the role of cannabinoid receptors in drug addiction. The present goal was to determine the less-explored interaction of SR-141716A and d-amphetamine in neurochemical and behavioral assays. Additionally, the effect of the substituents and substitution patterns on the phenyl ring located at the 5 position of SR-141716A (4-chlorophenyl), and of the CB 1/CB 2 cannabinoid receptor agonist WIN-55,212-2, was determined. SR-141716A, AM-251 (4-iodophenyl) and NIDA-41020 (4-methoxyphenyl) did not alter amphetamine-evoked [ 3H]overflow from rat striatal slices preloaded with [ 3H]dopamine. MRI-8273-30-1 (4-fluorophenyl; 0.1–10 μM) attenuated amphetamine (3 μM)-evoked [ 3H]overflow, and MRI-8273-59 (3,4-dichlorphenyl; 0.01–10 μM) augmented amphetamine (0.3–3 μM)-evoked [ 3H]overflow. WIN-55,212-2 was without effect. In a locomotor activity experiment, SR-141716A and MRI-8273-30-1 did not alter amphetamine-induced hyperactivity. However, MRI-8273-59 (1–3 mg/kg) dose-dependently attenuated amphetamine (1 mg/kg)-induced hyperactivity. The present results suggest that SR-141716A is less efficacious to alter amphetamine effects than its reported efficacy to diminish the effects of opiates and nicotine. Modification of the 5-phenyl position of SR-141716A affords compounds that do interact with amphetamine in vitro and in vivo.

Pharmacological analysis of cannabinoid-induced inhibition of gastric mucosal damage and gastric motility

Aims: Cannabinoid receptors are likely to be involved in different gastrointestinal functions: Δ9-tetrahydrocannabinol inhibits stress ulcer (Sofia et al., 1978), decreases intragastric pressure and the pyloric contractility (Krowicki et al.,1999) and CB1 receptor agonists decrease the gastric acid secretion (Adami et al., 2002). We aimed to detect the effect of endogenous cannabinoids (anandamide and methanadamide) and the synthetic analogue WIN-552, 212–2 on acid-independent ulcer model and stimulated gastric motility. Gastric mucosal damage was induced by acidified ethanol in rats. Gastric motility was tested by using the balloon method as described by LeFebvre et al.(1992) in the rats. Gastric motility was stimulated centrally by insulin (5 IU). The substances were given intravenously (i.v.) and intracerebroventricularly (i.c.v.). Results: It was found that: 1. Anandamide, methanandamide (1.3–5.2µmol/kg i.v.) and WIN-552,212–2 (0.09–0.2µmol/kg i.v.) inhibited the ethanol-induced gastric mucosal damage in a significant manner. Anandamide and methanandamide given i.c.v. inhibited the mucosal lesions in the doses range of 12.5–110 nmol/rat. 2. The gastro-protective effect of methanandamide was antagonized by the cannabinoid CB1 receptor antagonist SR 141716A as well as by the vanilloid receptor antagonist capsazepine, indicating that both CB1 and TRPV1 receptors may be involved in gastroprotective effect of cannabinoid receptor stimulants. 3. The µinsulin-induced enhanced gastric motor activity was reduced by anadamide and methanandamide (1.3–5.2µmol/kg, i.v.). This effect was reversed by SR 141716A (4.32µmol/kg, i.v.), but was only partially inhibited by capsazepine. Conclusion: 1. Cannabinoid CB1 receptors are likely to be involved in gastric mucosal defense. 2. Activation of CB1 receptors results in inhibition of stimulated gastric motor activity. 3. TRPV1 receptors may be involved in the gastroprotective effect of methanandamid, but only partially in the inhibition of gastric motility. The work was supported by ETT Grant 529

Effect of Cannabinoid CB1 Receptor Antagonist SR141714A and CB1 Receptor Knockout on Cue-Induced Reinstatement of Ensure® and Corn-Oil Seeking in Mice

The cannabinoid CB1 receptor antagonist SR141716A decreases cue-induced reinstatement of sucrose and drug seeking in rats. Reinstatement behavior is not well characterized in C57Bl/6 mice, including CB1 receptor knockout mice generated on a C57Bl/6 background. In the present study, male C57Bl/6, CB1 knockout (CB1 KO), and wild-type littermate (WT) mice were trained to respond for the sweet reinforcer Ensure or corn oil. Responding was maintained on a fixed ratio 1 (FR1) schedule of reinforcement for 10 days, and then extinguished by the removal of the reinforcer and associated cues. Subsequently, the effect of either pretreatment with SR141716A or CB1 receptor knockout on cue-induced reinstatement of Ensure or corn-oil seeking was assessed. Both 1.0 and 3.0 mg/kg SR141716A decreased reinstatement of Ensure seeking in C57Bl/6 mice. A tenfold higher dose of SR141716A (10.0 mg/kg) was required to attenuate reinstatement behavior in C57Bl/6 mice responding for corn oil, suggesting that CB1 receptors may be selectively involved in the neurobiology underlying reinstatement of responding for some food reinforcers but not others. Whereas CB1 receptor antagonism selectively attenuated reinstatement of responding for Ensure, genetic deletion of the CB1 receptor produced only a trend in decreasing reinstatement of Ensure seeking, and did not attenuate reinstatement of corn-oil seeking. Baseline differences in levels of operant responding were also observed in WT vs CB1 KO mice maintained by Ensure and corn oil. This and other possible reasons for the observed discrepancy between pharmacological blockade vs genetic invalidation of the CB1 receptor on reinstatement of Ensure seeking are discussed.

The cannabinoid CB1 receptor antagonist SR141716A (Rimonabant) enhances the metabolic benefits of long-term treatment with oleoylethanolamide in Zucker rats

Anandamide and oleoylethanolamide (OEA) are lipid mediators that regulate feeding and lipid metabolism. While anandamide, a cannabinoid CB1 receptor agonist, promotes feeding and lipogenesis, oleoylethanolamide, an endogenous agonist of peroxisome proliferator activated receptor alpha (PPAR-α), decreases food intake and activates lipid mobilization and oxidation. The treatment with a cannabinoid CB1 receptor antagonist results in reduction of body weight gain and cholesterol in obese humans and rodents. In the present study, we show the benefits of the treatment of obese Zucker rats with a combination of a cannabinoid CB1 receptor antagonist (Rimonabant) and oleoylethanolamide. This combinational therapy improved the separate effects of Rimonabant and OEA, and resulted in marked decreases on feeding, body weight gain, and plasma cholesterol levels. Additionally, the treatment with both drugs reduced the hepatic steatosis observed in Zucker rats, decreasing liver fat deposits and damage, as revealed by the levels of alanine aminotransferase activity in serum. The combined treatment inhibits the expression of stearoyl coenzyme-A desaturase-1 (SCD-1), a pivotal enzyme in lipid biosynthesis and triglyceride mobilization that is linked to obesity phenotypes. These results support the use of combined therapies with cannabinoid CB1 receptor antagonists and PPAR-α agonists for the treatment of obesity associated with dyslipemia.