Search

Amphotericin B (AmB) is a very effective antifungal agent, and resistance in clinical isolates is rare. However, clinical treatment with AmB is often associated with severe side effects. Reducing the administration dose of AmB by combining it with other agents is a promising strategy to minimize this toxicity. In this study, we screened a small compound library and observed that the anti-obesity drug rimonabant exhibited synergistic antifungal action with AmB against Candida species and Cryptococcus neoformans. Moreover, the combination of AmB and rimonabant exhibited synergistic or additive effects against Candida albicans biofilm formation and cell viability in preformed biofilms. The effects of this combination were further confirmed in vivo using a murine systemic infection model. Exploration of the mechanism of synergy revealed that rimonabant enhances the fungicidal activity of AmB by increasing cellular oxidative stress and cell membrane permeability. These findings provide a foundation for the possible development of AmB-rimonabant polytherapies for fungal infections., (© The Author(s) 2021. Published by Oxford University Press on behalf of FEMS.)

Across many species, endocannabinoids play an important role in regulating social play, reward, and anxiety. These processes are mediated through at least two distinct cannabinoid receptors (CB), CB1 and CB2. CB1 expression is found in appreciable densities across regions of the brain that integrate memory with socio-spatial information; many of these regions have been directly linked to the neurobiology of pair bonding in monogamous species. Using receptor autoradiography, we provide the first distributional map of CB1 within the brains of closely related monogamous prairie voles and promiscuous meadow voles, and compare receptor densities across sexes and species in limbic regions. We observe CB1-specific signal using [3H] CP-55,940 and [3H] SR141716A, though the latter exhibited a lower signal to noise ratio. We confirmed the presence of CB2 in prairie vole spleen tissue using [3H] CP-55,940. However, we found no evidence of CB2 in the brain using either [3H] CP-55,940 or [3H] A-836,339. The overall distribution of putative CB1 in the brain was similar across vole species and followed the pattern of CB1 expression observed in other species-high intensity binding within the telencephalon, moderate binding within the diencephalon, and mild binding within the mesencephalon and metencephalon (aside from the cerebellar cortex). However, we found profound differences in CB1 densities across species, with prairie voles having higher CB1 binding in regions implicated in social attachment and spatial memory (e.g., periaqueductal gray, hippocampus). These findings suggest that CB1 densities, but not distribution, correlate with the social systems of vole species., (© 2020 Wiley Periodicals LLC.)

Sarcopenia is an age-related loss of muscle mass associated with changes in skeletal muscle protein homeostasis due to lipid accumulation and anabolic resistance; changes that are also commonly described in obesity. Activation of the endocannabinoid system is associated with the development of obesity and insulin resistance, and with the perturbed skeletal muscle development. Taken together this suggests that endocannabinoids could be regulators of skeletal muscle protein homeostasis. Here we report that rimonabant, an antagonist for the CB1 receptor, can prevent dexamethasone-induced C2C12 myotube atrophy without affecting the mRNA expression of atrogin-1/MAFbx (a marker of proteolysis), which suggests it is involved in the control of protein synthesis. Rimonabant alone stimulates protein synthesis in a time- and dose-dependent manner through mTOR- and intracellular calcium-dependent mechanisms. CB1 agonists are unable to modulate protein synthesis or prevent the effect of rimonabant. Using C2C12 cells stably expressing an shRNA directed against CB1, or HEK293 cells overexpressing HA-tagged CB1, we demonstrated that the effect of rimonabant is unaffected by CB1 expression level. In summary, rimonabant can stimulate protein synthesis in C2C12 myotubes through a CB1-independent mechanism. These results highlight the need to identify non-CB1 receptor(s) mediating the pro-anabolic effect of rimonabant as potential targets for the treatment of sarcopenia, and to design new side-effect-free molecules that consolidate the effect of rimonabant on skeletal muscle protein synthesis., (© 2020 Wiley Periodicals LLC.)

Rationale: The emergence of the consumption of highly potent synthetic cannabinoid receptor agonists (spice drugs) that produce important neurological symptoms has prompted the research on the consequences of acute and chronic use of these new psychoactive substances. Most studies on cannabinoid dependence have been performed in male animals, and there is a need of studies using female subjects., Objectives: In the present study, we evaluated only in female animals the role of dopamine D1 receptors in the behavioral responses induced by acute and repeated stimulation of cannabinoid CB1 receptors, including the development of physical dependence, since cannabinoid CB1 receptors are co-localized with dopamine D1 receptors on GABAergic neurons projecting to the substantia nigra., Methods: To this end, female dopamine D1 receptor-deficient mice and wild-type littermates were treated with HU-210, a potent synthetic cannabinoid agonist., Results: Mutant mice displayed an enhanced response to acute motor and hypothermic effects to HU-210 when compared with wild-type females. The administration of SR141716A precipitated behavioral signs of withdrawal in mice treated subchronically with HU-210. Severity of cannabinoid withdrawal syndrome was potentiated in dopamine D1-deficient female mice. Indeed, 4 of 6 abstinence signs were increased in mutant mice., Conclusions: These results support for a role of dopamine D1 receptors in the acute, chronic, and withdrawal actions of spice drugs.

The endocannabinoid, anandamide (AEA), stimulates cannabinoid receptors (CBRs) and is enriched in the kidney, especially the renal medulla. AEA infused into the renal outer medulla of mice stimulates urine flow rate and salt excretion. Here we show that these effects are blocked by the CBR type 1 (CB1) inverse agonist, rimonabant. Immunohistochemical analysis demonstrated the presence of CB1 in thick ascending limb (TAL) tubules. Western immunoblotting demonstrated the presence of CB1 (52 kDa) in the cortex and outer medulla of mouse kidney. The effect of direct [CP55940 (CP) or AEA] or indirect [fatty acyl amide hydrolase (FAAH) inhibitor, PF3845 (PF)] cannabinoidimetics on Na + transport in isolated mouse TAL tubules was studied using the Na + -sensitive dye, SBFI-AM. Switching from 0 Na + solution to control Ringer's solution (CR) rapidly increased TAL cell [Na + ] i Addition of CP to CR produced a further elevation, similar in magnitude to that of ouabain, a Na + -K + -ATPase inhibitor. This [Na + ] i -elevating effect of CP was time-dependent, required the presence of Na + in the bathing solution, and was insensitive to Na + -K + -2Cl - cotransporter inhibition. Addition of PF to CR elevated [Na + ] i in FAAH wild-type but not FAAH knockout (KO) TALs, whereas the additions of CP and AEA to PF-treated FAAH KO TALs increased [Na + ] i An interaction between cannabinoidimetics and ouabain (Ou) was observed. Ou produced less increase in [Na + ] i after cannabinoidimetic treatment, whereas cannabinoidimetics had less effect after Ou treatment. It is concluded that cannabinoidimetics, including CP and AEA, inhibit Na + transport in TALs by inhibiting Na + exit via Na + -K + -ATPase. SIGNIFICANCE STATEMENT: Cannabinoids including endocannabinoids induce renal urine and salt excretion and are proposed to play a physiological role in the regulation of blood pressure. Our data suggest that the mechanism of the cannabinoids involves inhibition of the sodium pump, Na + -K + -ATPase, in thick ascending limb cells and, likely, other proximal and distal tubular segments of the kidney nephron., (Copyright © 2020 by The American Society for Pharmacology and Experimental Therapeutics.)

Pharmacological blockade of the cannabinoid type 1 receptor, a G protein-coupled receptor expressed in the central nervous system and various peripheral tissues, reverses diet-induced obesity and dyslipidemia through the reduction of food intake and altered nutrient partitioning. This strategy is being explored for a number of therapeutic applications; however, its potency for the treatment of atherosclerotic cardiovascular disease via improvements in lipid metabolism remains unclear. Therefore, here, we aimed to investigate whether inhibition of the endocannabinoid system can attenuate atherosclerosis development through improvement of dyslipidemia. Lean, dyslipidemic female APOE∗3-Leiden.CETP transgenic mice were fed a Western-type diet supplemented with or without the cannabinoid type 1 receptor inverse agonist rimonabant (20 mg·kg body weight -1  day -1 ) for up to 20 weeks. Plasma lipids and bile acids were determined, and atherosclerotic lesions were scored in the aortic valve region. Rimonabant lowered plasma levels of triglyceride (TG) (-56%) and non-HDL-C (-19%) and increased HDL-C (+57%). These effects were explained by decreased VLDL-TG production (-52%) and accelerated VLDL-TG turnover accompanied by pronounced browning of white adipose tissue. In addition, rimonabant attenuated reverse cholesterol transport (-30%), increased plasma bile acid levels (+160%), and increased hepatic cholesterol accumulation (+88%). Importantly, rimonabant markedly lowered atherosclerotic lesion size (-64%), which coincided with decreased lesion severity (28% vs. 56% severe lesions) and which strongly correlated with non-HDL-C exposure (R 2  = 0.60). Taken together, inhibition of the endocannabinoid system potently reverses dyslipidemia and prevents atherogenesis, even in the absence of obesity., Competing Interests: Conflict of interest T. C. is an employee and shareholder of Eli Lilly and Company. Eli Lilly and Company had no role in study design, data collection and analysis, decision to publish, or preparation of the article. All other authors declare that they have no conflicts of interest with the contents of this article., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

In animals, research in the past two decades has demonstrated the strong involvement of the endocannabinoid system (ECS) in numerous steps of the reproductive process, including ovarian physiology. Reproductive lifespan is closely related to the number of nongrowing ovarian follicles, called ovarian reserve (OR), which is definitively established during foetal life. Thus, OR damage may lead to poor reproductive outcomes and a shortened reproductive lifespan. We investigated whether prenatal ECS modulation had an effect on the OR at different ages in the rat offspring. Four groups of gestating female rats (F0) were exposed to the CB1-/CB2-receptor agonist WIN55212 (0.5 mg/kg), the CB1R inverse agonist SR141716 (3 mg/kg) or Δ9THC (5 mg/kg) and were compared to negative control groups. OR was histologically assessed at different postnatal timepoints (F1 individuals): postnatal day (PND) 6, PND40 and PND90. At PND6, prenatal exposure had no effect on OR. In the young adult group (PND90) exposed during gestation to WIN55212, we observed a CB1R-mediated delayed OR decrease, which was reversed by prenatal CB1R blockade by SR141716. Conversely, after prenatal SR141716 exposure, we observed higher OR counts at PND90. RT-PCR experiments also showed that prenatal ECS modulation perturbed the mRNA levels of ECS enzymes and OR regulation genes. Our findings support the role of the ECS in OR regulation during the foetal life of rats and highlight the need for further studies to elucidate its precise role in OR physiology.

Stimulation of cannabinoid CB 1 receptors generally increases ingestion. However, the non-selective cannabinoid receptor agonist HU-210 exerts the opposite effect. The first objective of this study was to investigate the role of CB 1 receptors in this "atypical" effect. Studies on the endocannabinoid system investigating the microstructure of licking for palatable solutions reported inconsistent results as for the role of CB 1 receptors in "liking" and "wanting". The second objective was to deal with these inconsistencies investigating the within-session time-course of licking-burst number. The microstructure of licking for a 10% sucrose solution in 30-min sessions was analysed in two experiments. In Experiment 1, the effect of the CB 1 receptor antagonist-inverse agonist rimonabant (0.5, 1 mg/kg) on HU-210 effect (100 μg/kg) was investigated. A dose range of HU-210 (25, 50, 100 μg/kg) was examined in Experiment 2. In Experiment 1, both HU-210 and rimonabant reduced licking due to reduced burst number. Moreover, HU-210 reduced the intra-burst lick rate, an index of motor competence. HU-210 effects were antagonised by rimonabant, and vice versa. Rimonabant decreased burst number late in the session at 0.5 mg/kg, and since the beginning of the session at 1 mg/kg. In Experiment 2, HU-210 failed to affect overall ingestion. These results suggest that HU-210 effect - when present - depends on CB 1 receptor stimulation, possibly leading to impairment of the motor competence necessary for licking. The reduction of burst number late in the session observed with rimonabant 0.5 mg/kg, which resembles the effect of reward devaluation, might suggest reduced "liking"., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Aims: Endocannabinoids are lipid mediators involved in the regulation of glucose homeostasis. They interact with the canonical cannabinoid receptors CB 1 and CB 2 , and it is now apparent that some cannabinoid receptor ligands are also agonists at GPR55. Thus, CB 1 antagonists such as SR141716A, also known as rimonabant, and AM251 act as GPR55 agonists in some cell types. The complex pharmacological properties of cannabinoids make it difficult to fully identify the relative importance of CB 1 and GPR55 in the functional effects of SR141716A, and AM251. Here, we determine whether SR141716A and AM251 regulation of mouse and human islet function is through their action as GPR55 agonists., Methods: Islets isolated from Gpr55 +/+ and Gpr55 -/- mice and human donors were incubated in the absence or presence of 10 µM SR141716A or AM251, concentrations that are known to activate GPR55. Insulin secretion, cAMP, IP 1 , apoptosis and β-cell proliferation were quantified by standard techniques., Results: Our results provide the first evidence that SR141716A and AM251 are not GPR55 agonists in islets, as their effects are maintained in islets isolated from Gpr55 -/- mice. Their signalling through G q -coupled cascades to induce insulin secretion and human β-cell proliferation, and protect against apoptosis in vitro, indicate that they have direct beneficial effects on islet function., Conclusion: These observations may be useful in directing development of peripherally restricted novel therapeutics that are structurally related to SR141716A and AM251, and which potentiate glucose-induced insulin secretion and stimulate β-cell proliferation.

Background: Ethanol (EtOH) self-administration is particularly sensitive to the modulation of CB 1 signaling in the nucleus accumbens (NAc) shell, and EtOH consumption increases extracellular levels of the endogenous cannabinoid CB 1 receptor agonist 2-arachidonoyl glycerol (2-AG) in this brain region. Stimulation of CB 1 receptor with agonists increases EtOH consumption, suggesting that EtOH-induced increases in 2-AG might sustain motivation for EtOH intake., Methods: In order to further explore this hypothesis, we analyzed the alterations in operant EtOH self-administration induced by intra-NAc shell infusions of 2-AG itself, the CB 1 inverse agonist SR141716A, the 2-AG clearance inhibitor URB602, anandamide, and the cyclooxygenase-2 (COX-2) inhibitor nimesulide., Results: Surprisingly, self-administration of 10% EtOH was dose-dependently reduced by either intra-NAc shell SR141716A or 2-AG infusions. Similar effects were found by intra-NAc shell infusions of URB602, suggesting again a role for accumbal 2-AG on the modulation of EtOH intake. Intra-NAc shell anandamide did not alter EtOH self-administration, pointing to a specific role for 2-AG in the modulation of EtOH self-administration. Finally, the inhibitory effect of intra-NAc shell 2-AG on EtOH intake was significantly reversed by pretreatment with nimesulide, suggesting that oxidative metabolites of 2-AG might mediate these inhibitory effects on operant self-administration., Conclusions: We propose that 2-AG signaling in the NAc exerts an inhibitory influence on EtOH consumption through a non-CB1 receptor mechanism involving the COX-2 pathway., (© 2020 by the Research Society on Alcoholism.)

The use of Δ 9 -tetrahydrocannabinol (THC) by inhalation using e-cigarette technology grows increasingly popular for medical and recreational purposes. This has led to development of e-cigarette based techniques to study the delivery of THC by inhalation in laboratory rodents. Inhaled THC reliably produces hypothermic and antinociceptive effects in rats, similar to effects of parenteral injection of THC. This study was conducted to determine the extent to which the hypothermic response depends on interactions with the CB 1 receptor, using pharmacological antagonist (SR141716, AM-251) approaches. Groups of rats were implanted with radiotelemetry devices capable of reporting activity and body temperature, which were assessed after THC inhalation or injection. SR141716 (4 mg/kg, i.p.) blocked or attenuated antinociceptive effects of acute THC inhalation in male and female rats. SR141716 was unable to block the initial hypothermia caused by THC inhalation, but temperature was restored to normal more quickly. Alterations in antagonist pre-treatment time, dose and the use of a rat strain with less sensitivity to THC-induced hypothermia did not change this pattern. Pre-treatment with SR141716 (4 mg/kg, i.p.) blocked hypothermia induced by i.v. THC and reversed hypothermia when administered 45 or 90 min after THC (i.p.). SR141716 and AM-251 (4 mg/kg, i.p.) sped recovery from, but did not block, hypothermia caused by vapor THC in female rats made tolerant by prior repeated THC vapor inhalation. The CB 2 antagonist AM-630, had no effect. These results suggest that hypothermia consequent to THC inhalation is induced by other mechanisms in addition to CB 1 receptor activation., Competing Interests: Declaration of Competing Interest SAV has consulted for LJARI., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Background: Recent years have seen a rise in the diversity and use of synthetic cannabinoids. The present study evaluated the behavioral effects of the third-generation indazole-3-carboxamide-type synthetic cannabinoid, AB-FUBINACA., Methods: Adult male and female C57BL/6J mice were treated with AB-FUBINACA (0-3 mg/kg, i.p.) and tested repeatedly in the tetrad battery measuring catalepsy, antinociception, hypothermia, and locomotor activity. Mice treated with AB-FUBINACA (≥2 mg/kg, i.p.) displayed classic cannabinoid effects in the tetrad that were blocked by the CB 1 receptor selective antagonist rimonabant. To address tolerance and withdrawal effects, a second group of mice was injected with AB-FUBINACA (3 mg/kg, s.c.) or vehicle consisting of 5% ethanol, 5% Kolliphor EL, and 90 % saline every 12 h and tested daily in modified tetrad over the course of 5 days. On the 6th day, withdrawal was precipitated using rimonabant (3 mg/kg, s.c.), and somatic signs of withdrawal (i.e., head twitches and paw tremors) were quantified., Results: Although mice did not develop tolerance to AB-FUBINACA or cross-tolerance to Δ 9 -tetrahydrocannabinol (THC; 50 mg/kg, i.p.), somatic precipitated withdrawal signs were observed. Repeated tetrad testing up to 48 h post injection indicated that AB-FUBINACA effects are relatively short-lived, as compared with THC. Brain levels of AB-FUBINACA, as quantified by UHPLC-MS/MS, were undetectable 4 h post injection., Conclusions: These data indicate that the cannabinoid effects of AB-FUBINACA are relatively short-lived, yet sufficient to induce dependence in mice., Competing Interests: Declaration of Competing Interest None., (Copyright © 2020 The Author(s). Published by Elsevier B.V. All rights reserved.)

AKB48 and its fluorinated derivative 5F-AKB48 are synthetic cannabinoids (SCs) which have caused hospitalizations and deaths in human users. Abuse of SCs is dangerous because users may mistake them for natural cannabis, which is generally considered to be unlikely to elicit adverse effects. The present studies were designed to investigate the in vitro oxidative metabolism of 5F-AKB48 by human microsomal fractions from different organs and sexes as well as recombinant human cytochrome P450s (P450s). Mass spectrometry data tentatively provides evidence for the existence of mono-, di-, and trihydroxylated metabolites in a successive metabolism. Experiments utilizing P450s revealed that the most active enzymes (CYP2D6, CYP2J2, CYP3A4, and CYP3A5) effectively produced mono- and dihydroxylated metabolites, while CYP3A4/5 also produced significant amounts of the trihydroxylated metabolite. Moreover, although the affinity and potency of Phase I metabolite 4OH-5F-AKB48 is reduced when compared to that of the parent drug, this metabolite nevertheless retains similar high affinity for CB1 receptors, and greater efficacy for G protein activation, when compared to THC. Finally, 5F-AKB48 produced time- and dose-dependent cannabimimetic effects in mice which were more potent, but shorter acting, than those of Δ 9 -THC, and were attenuated by prior treatment with the CB1 antagonist rimonabant. Based on our data, we hypothesize that while many cases of toxicity result from genetic mutations, which can lead to a decrease or even absence of activity for Phase I drug-metabolizing enzymes, other P450s could potentially increase their role in the metabolism of these SCs. Because many metabolites of SCs remain biologically active, they could contribute to the deleterious effects of these substances., Competing Interests: Declaration of competing interest The authors declare no conflict of interest., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Cannabinoid subtype 1 receptor (CB1R) antagonists were originally developed as anti-obesity agents. Unfortunately, SR1417116A (rimonabant), the first marketed inverse agonist of CB1R, produced CNS-related adverse effects including depression and suicidal ideation, and thus it was withdrawn from the market. These effects of rimonabant became evident in patients following chronic dosing. Standard preclinical toxicity studies failed to detect these adverse effects. The goal of these studies was to perform an integrated battery of behavioral assays to better understand the behavioral effects of rimonabant following both acute and chronic administration. In the present study, acute dosing with rimonabant in rats significantly decreased food consumption; decreased measures of locomotor activity; increased scratching, grooming and wet-dog shakes; and increased defecation. Subsequently, animals were tested using a chronic dosing regimen but prior to drug administration for that day. The highest dose of rimonabant tested significantly decreased marble burying behavior, presumably anxiolysis. There were also significant effects in social interaction after chronic dosing. Our results did not reveal significant rimonabant-induced anxiogenic behaviors. Future studies to characterize behavioral screens for anxiogenic effects of CB1 antagonists in rodents should further explore social interaction paradigms and potential comorbid factors of rimonabant dosing such as sex, age, and obesity., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Excessive activation of the sympatho-adrenomedullary system plays a pathogenic role in triggering and sustaining essential hypertension. We previously reported that, in normotensive rats, intracerebroventricularly (i.c.v.) administered neuropeptides, corticotropin-releasing factor and bombesin induced activation of the sympatho-adrenomedullary system, and that brain cannabinoid CB 1 receptors negatively regulated this activation. In this study, we investigated the effects of brain CB 1 receptor stimulation on blood pressure and the sympatho-adrenomedullary outflow in spontaneously hypertensive rats (SHRs), commonly used animal models of essential hypertension, and in Wistar-Kyoto (WKY) rats, normotensive controls of SHRs. In 18-week-old SHRs and WKY rats under urethane anaesthesia (1.0 g/kg, i.p.), SHRs exhibited significantly higher systolic, mean and diastolic blood pressures and plasma noradrenaline and adrenaline, and a lower heart rate than WKY rats. Single administration of arachidonyl 2'-chloroethylamide (ACEA, CB 1 agonist, 1.4 µmol/animal, i.c.v.) significantly but partially reduced mean and diastolic blood pressures and the plasma level of noradrenaline in SHRs compared to vehicle (N,N-dimethylformamide)-treated SHRs. These ACEA-induced reductions were abolished by central pretreatment with rimonabant (CB 1 antagonist, 300 nmol/animal, i.c.v.), which alone showed no significant effect on blood pressures or plasma noradrenaline and adrenaline levels of SHRs. On the other hand, ACEA had no significant effect on blood pressure or plasma noradrenaline and adrenaline levels in WKY rats. These results suggest that stimulation of brain CB 1 receptors can ameliorate hypertension accompanied by enhanced sympathetic outflow without affecting blood pressure under normotensive conditions., (© 2020 John Wiley & Sons Australia, Ltd.)

Chronic infection with hepatitis B virus (HBV) sometime induces lethal cirrhosis and hepatocellular carcinoma. Although nucleot(s)ide analogs are used as main treatment for HBV infection, the emergence of the drug-resistant viruses has become a problem. To discover novel antivirals with low side effects and low risk of emergence of resistant viruses, screening for anti-HBV compounds was performed with compound libraries of inhibitors targeting G-protein-coupled receptors (GPCRs). HepG2-hNTCP C4 cells infected with HBV were treated with various GPCR inhibitors and harvested at 14 day postinfection for quantification of core protein in the first screening or relaxed circular DNA in the second screening. Finally, we identified a cannabinoid receptor 1 inhibitor, rimonabant, as a candidate showing anti-HBV effect. In HepG2-hNTCP C4 cells, treatment with rimonabant suppressed HBV propagation at the viral RNA transcription step but had no effect on entry or covalently closed circular DNA level. The values of half maximal inhibitory concentration, half maximal effective concentration, and selectivity index of rimonabant in primary human hepatocyte (PHH) are 2.77 μm, 40.4 μm, and 14.6, respectively. Transcriptome analysis of rimonabant-treated primary hepatocytes by RNA sequencing revealed that the transcriptional activity of hepatocyte nuclear factor 4α (HNF4α), which is known to stimulate viral RNA synthesis, was depressed. By treatment of PHH with rimonabant, the expression level of HNF4α protein and the production of the messenger RNAs (mRNAs) of downstream factors promoted by HNF4α were reduced while the amount of HNF4α mRNA was not altered. These results suggest that treatment with rimonabant suppresses HBV propagation through the inhibition of HNF4α activity., (© 2020 The Societies and John Wiley & Sons Australia, Ltd.)

Parkinson's disease (PD) is characterized by the selective loss of nigrostriatal dopamine neurons associated with microglial activation. Inhibition of the inflammatory response elicited by activated microglia could be an effective strategy to alleviate the progression of PD. Here, we synthesized 2-(5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazol-3-yl)-N-(2-hydroxyethyl)-2-oxoacetamide (CDMPO) and studied its protective anti-inflammatory mechanisms following lipopolysaccharide (LPS)-induced neuroinflammation in vitro and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced neurotoxicity in vivo. CDMPO and its parent compound, rimonabant, significantly attenuated nitric oxide (NO) production in LPS-stimulated primary microglia and BV2 cells. Furthermore, CDMPO significantly inhibited the release of proinflammatory cytokines and prostaglandin E2 (PGE 2 ) by activated BV2 cells, also suppressed expression of inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2). Mechanistically, CDMPO attenuated LPS-induced activation of nuclear factor-kappa B (NF-κB), inhibitor of kappa B alpha (IκBα), and p38 phosphorylation in BV2 cells. MPTP intoxication of mice results in glial activation, tyrosine hydroxylase (TH) depletion, and significant behavioral deficits. Prophylactic treatment with CDMPO decreased proinflammatory molecules via NF-κB and p38 mitogen-activated protein kinase signaling, resulting in protection of dopaminergic neurons and improved behavioral impairments. These results suggest that CDMPO is a promising neuroprotective agent for the prevention and treatment of microglia-mediated neuroinflammatory conditions and may be useful for behavioral improvement in PD phenotype., Competing Interests: Declaration of competing interest The authors declare that they have no competing interests., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Human adipose tissue includes large quantities of mesenchymal stromal cells (atMSCs), which represent an abundant cell source for therapeutic applications in the field of regenerative medicine. Adipose tissue secrets various soluble factors including endocannabinoids, and atMSCs express the cannabinoid receptors CB1 and CB2. This indicates that adipose tissue possesses an endocannabinoid system (ECS). The ECS is also ascribed great significance for wound repair, e.g. by modulating inflammation. However, the exact effects of CB1/CB2 activation in human atMSCs have not been investigated, yet. In the present study, we stimulated human atMSCs with increasing concentrations (1-30 μM) of the unspecific cannabinoid receptor ligand WIN55,212-2 and the specific CB2 agonist JWH-133, either alone or co-applied with the receptor antagonist Rimonabant (CB1) or AM 630 (CB2). We investigated the effects on metabolic activity, cell number, differentiation and cytokine release, which are important processes during tissue regeneration. WIN decreased metabolic activity and cell number, which was reversed by Rimonabant. This suggests a CB1 dependent mechanism, whereas the number of atMSCs was increased after CB2 ligation. WIN and JWH increased the release of VEGF, TGF-β1 and HGF. Adipogenesis was enhanced by WIN, which could be reversed by blocking CB1. There was no effect on osteogenesis, and only WIN increased chondrogenic differentiation. Our results indicate that definite activation of the cannabinoid receptors exerted different effects in atMSCs, which could be of specific value in cell-based therapy for wound regeneration., Competing Interests: Declaration of competing interest No potential conflicts of interest, financial or otherwise are declared by the authors. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors., (Copyright © 2020 Elsevier Inc. All rights reserved.)

A survey of the literature indicates that both rapid eye movement sleep deprivation (RSD) and activation of cannabinoid CB 1 receptor (CB 1 R) may impair novel object recognition (NOR) memory in rodents. To our knowledge, so far, no previous study has investigated the probable effects of RSD on the different phases of NOR memory. Moreover, far too little attention has been paid to the potential role of the CB 1 R in the effects of RSD on object memory. Therefore, the major objective of this study was to investigate the probable role of the CB 1 R in the acquisition, consolidation, retrieval, and reconsolidation of NOR memory in the RSD rats. A 12-h paradigm of RSD using the multiple platform method did not affect acquisition, but it impaired the consolidation, retrieval, and reconsolidation of NOR memory. Administration of the CB 1 R antagonist rimonabant (1 or 3 mg/kg, i.p.) did not have significant effects on the acquisition and reconsolidation, but it improved RSD-induced impairment of the consolidation and retrieval of object memory, especially at the dose of 3 mg/kg. In addition, the RSD paradigm did not affect the levels of plasma corticosterone as an important marker of stress in rat. The results revealed that RSD may have different effects on the different phases of NOR memory which may not be attributable to the effects of stress. Our findings would seem to suggest that the CB 1 R can be targeted to, at least partially, modulate the adverse effects of RSD on the process of NOR memory., (Copyright © 2019. Published by Elsevier B.V.)

In the present study, we examined whether LDK1258, which produces strong CB 1 receptor allosteric effects in in vitro assays, would elicit in vivo effects consistent with allosteric activity. In initial studies, LDK1258 reduced food consumption and elicited delayed antinociceptive effects in the chronic constrictive injury of the sciatic nerve (CCI) model of neuropathic pain, which unexpectedly emerged 4 h post-injection. UPLC-MS/MS analysis quantified significant levels of LDK1258 in both blood and brain tissue at 30 min post-administration that remained stable up to 4 h. The observation that LDK1258 also produced respective antinociceptive and anorectic effects in rimonabant-treated wild type mice and CB 1 (-/-) mice suggests an off-target mechanism of action. Likewise, LDK1258 produced a partial array of common cannabimimetic effects in the tetrad assay, which were not CB 1 receptor mediated. Additionally, LDK1258 did not substitute for the CB 1 receptor orthosteric agonists CP55,940 or anandamide in the drug discrimination paradigm. In other in vivo assays sensitive to CB 1 receptor allosteric modulators, LDK1258 failed to shift the dose-response curves of either CP55,940 or anandamide in producing thermal antinociception, catalepsy, or hypothermia, and did not alter the generalization curve of either drug in the drug discrimination assay. Thus, this battery of tests yielded results demonstrating that LDK1258 produces antinociceptive effects in the CCI model of neuropathic pain, anorectic effects, and other in vivo pharmacological effects in a manner inconsistent with CB 1 receptor allosterism. More generally, this study offers a straightforward screening assay to determine whether newly synthesized CB 1 receptor allosteric modulators translate to the whole animal., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Endocannabinoids regulate different aspects of neurodevelopment. In utero exposure to the exogenous psychoactive cannabinoid Δ 9 -tetrahydrocannabinol (Δ 9 -THC), has been linked with abnormal cortical development in animal models. However, much less is known about the actions of endocannabinoids in human neurons. Here we investigated the effect of the endocannabinoid 2-arachidonoyl glycerol (2AG) and Δ 9 -THC on the development of neuronal morphology and activation of signaling kinases, in cortical neurons derived from human induced pluripotent stem cells (hiPSCs). Our data indicate that the cannabinoid type 1 receptor (CB1R), but not the cannabinoid 2 receptor (CB2R), GPR55 or TRPV1 receptors, is expressed in young, immature hiPSC-derived cortical neurons. Consistent with previous reports, 2AG and Δ 9 -THC negatively regulated neurite outgrowth. Interestingly, acute exposure to both 2AG and Δ 9 -THC inhibited phosphorylation of serine/threonine kinase extracellular signal-regulated protein kinases (ERK1/2), whereas Δ 9 -THC also reduced phosphorylation of Akt (aka PKB). Moreover, the CB1R inverse agonist SR 141716A attenuated the decrease in neurite outgrowth and ERK1/2 phosphorylation induced by 2AG and Δ 9 -THC. Taken together, our data suggest that hiPSC-derived cortical neurons express CB1Rs and are responsive to exogenous cannabinoids. Thus, hiPSC-neurons may represent a good cellular model for investigating the role of the endocannabinoid system in regulating cellular processes in developing human neurons., Competing Interests: Declaration of competing interest Authors declare no conflict of interest., (Copyright © 2019. Published by Elsevier Inc.)

(1) Background: Acute administration of the cannabinoid receptor 1 (CB1R) inverse agonist Rimonabant (SR141716A) to fed Wistar rats was shown to elicit a rapid and short-lasting elevation of serum free fatty acids. (2) Methods: The effect of Rimonabant on lipolysis in isolated primary rat adipocytes was studied to raise the possibility for direct mechanisms not involving the (hypothalamic) CB1R. (3) Results: Incubation of these cells with Rimonabant-stimulated lipolysis to up to 25% of the maximal isoproterenol effect, which was based on both CB1R-dependent and independent mechanisms. The CB1R-dependent one was already effective at Rimonabant concentrations of less than 1 µM and after short-term incubation, partially additive to β-adrenergic agonists and blocked by insulin and, in part, by adenosine deaminase, but not by propranolol. It was accompanied by protein kinase A (PKA)-mediated association of hormone-sensitive lipase (HSL) with lipid droplets (LD) and dissociation of perilipin-1 from LD. The CB1R-independent stimulation of lipolysis was observed only at Rimonabant concentrations above 1 µM and after long-term incubation and was not affected by insulin. It was recapitulated by a cell-free system reconstituted with rat adipocyte LD and HSL. Rimonabant-induced cell-free lipolysis was not affected by PKA-mediated phosphorylation of LD and HSL, but abrogated by phospholipase digestion or emulsification of the LD. Furthermore, LD isolated from adipocytes and then treated with Rimonabant (>1 µM) were more efficient substrates for exogenously added HSL compared to control LD. The CB1R-independent lipolysis was also demonstrated in primary adipocytes from fed rats which had been treated with a single dose of Rimonabant (30 mg/kg). (4) Conclusions: These data argue for interaction of Rimonabant (at high concentrations) with both the LD surface and the CB1R of primary rat adipocytes, each leading to increased access of HSL to LD in phosphorylation-independent and dependent fashion, respectively. Both mechanisms may lead to direct and acute stimulation of lipolysis at peripheral tissues upon Rimonabant administration and represent targets for future obesity therapy which do not encompass the hypothalamic CB1R.

The brain endocannabinoid system has been shown to play a role in many physiological processes, including mood, learning and memory. It is also involved in the pathogenesis of anxiety, depression, mood disorders, as well as neurodegenerative disorders, although the exact mechanisms by which cannabinoid receptors interfere in these disorders are not well established. The aim of the present study was to evaluate the effects of cannabinoid ligands HU‑210 (CB1 receptor agonist) and SR 141716A (CB1 receptor antagonist) on learning and memory processes of rats with depressive - like state, induced by bilateral olfactory bulbectomy. The bilateral olfactory bulbectomy (OBX) is a validated model of depression, which can be used also as an animal model of Alzheimer's disease. We found that the subchronic treatment of OBX rats with HU 210 and SR 141716A exerted modulatory effect on rat's performance in both active avoidance (shuttle box) and passive avoidance (step through) tests. HU 210 ameliorated the memory deficits of OBX rats; however, the scores of the sham‑operated controls had not been reached. SR 141716A modified the avoidance performance in OBX rats and showed a memory enhancing effect in the sham‑operated rats. Our findings suggest that CB1 receptors might be involved in avoidance learning and memory acquisition in OBX rats.

The endocannabinoid system (ECS) is known to modulate not only food intake but also pain, especially via the cannabinoid type 1 receptor (CB1R) expressed throughout the central nervous system and the peripheral tissues. Our previous study demonstrated that fasting produces an analgesic effect in adult male mice, which is reversed by intraperitoneal (i.p.) administration of CB1R antagonist (SR 141716). In the present study, we further examined the effect of CB1R expressed in the peripheral tissues. In the formalin-induced inflammatory pain model, i.p. administration of peripherally restricted CB1R antagonist (AM 6545) reversed fasting-induced analgesia. However, intraplantar administration of SR 141716 did not affect fasting-induced analgesia. Furthermore, mRNA expression of CB1R did not change in the formalin model by fasting in the dorsal root ganglia. The formalin-induced c-Fos expression at the spinal cord level was not affected by fasting, and in vivo recording from the superficial dorsal horn of the lumbar spinal cord revealed that fasting did not affect formalin-induced neural activity, which indicates minimal involvement of the spinal cord in fasting-induced analgesia. Finally, when we performed subdiaphragmatic vagotomy to block the hunger signal from the gastrointestinal (GI) system, AM 6545 did not affect fasting-induced analgesia, but SR 141716 still reversed fasting-induced analgesia. Taken together, our results suggest that both peripheral and central CB1Rs contribute to fasting-induced analgesic effects and the CB1Rs in the GI system which transmit fasting signals to the brain, rather than those in the peripheral sensory neurons, may contribute to fasting-induced analgesic effects.

CB1 receptor antagonists disrupt operant responding for food and drug reinforcers, and cue-induced reinstatement of cocaine and heroin seeking. Conversely, enhancing endocannabinoid signaling, particularly 2-arachidonyl glycerol (2-AG), by inhibition of monoacyl glycerol lipase (MAGL), may facilitate some aspects of reward seeking. To determine how endocannabinoid signaling affects responding to reward-predictive cues, we employed an operant task that allows us to parse the incentive motivational properties of cues. Rats were required to nosepoke during an intermittent audiovisual incentive cue (IC) to obtain a 10% sucrose reward. The CB1 receptor antagonist, rimonabant, dose-dependently decreased the response ratio (rewarded ICs/total presented) and active nosepokes per IC, while it increased the latency to respond to the cue and obtain the reward, indicating an overall decrease in both the choice and vigor of responding. Yet rats persisted in entering the reward cup. Using a modified version of the task, the novel MAGL inhibitor MJN110 increased the response ratio, decreased the latencies to respond to the IC and enhanced active nosepokes per IC, indicating a facilitation of cue-induced reward seeking. These effects were blocked by a subthreshold dose of rimonabant. Finally, MJN110 did not alter consumption of freely available sucrose within volumes obtained in the operant task. Together these data demonstrate blocking endocannabinoid tone at the CB1 receptor attenuates the ability of cues to induce reward seeking, while some aspects of motivation for the reward are retained. Conversely, enhancing 2-AG signaling at CB1 receptors facilitates IC responding and increases the motivational properties of the IC., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Objectives: To determine if diminished orthosteric agonist binding due to mutations in extracellular loops 1 or 2 of the cannabinoid receptor 1 (CB 1 ) can be overcome by an allosteric modulator and restore agonist binding., Methods: Binding assays were performed using a range of concentrations of orthosteric compound, in the presence or absence of a set concentration of the allosteric modulator PSNCBAM-1 to determine the EC 50 in its absence or presence., Key Findings: Single mutations in extracellular loop 1 or 2 of CB 1 showed weak or no binding of agonist CP55940 to the receptor. Interestingly, upon addition of the allosteric modulator PSNCBAM-1, this binding was restored typically to wild-type CB 1 levels. In a few cases, the allosteric modulator ORG27569 was compared with PSNCBAM-1 for CP55940 binding and it also restored binding. Further, wild-type levels of inverse agonist bound the CB 1 mutants in the absence of modulator, suggesting the mutants were originally folded like the wild type., Conclusions: Based on our findings, we provide evidence of a therapeutic application for allosteric modulators in situations where a mutation in the receptor may hinder its function. By utilizing allosteric modulators, restoration of orthosteric binding may be possible., (© 2019 Royal Pharmaceutical Society.)

Osteoarthritis (OA) is characterized by cartilage degeneration, subchondral sclerosis, and pain. Cannabinoids have well-established anti-nociceptive properties in animal models of chronic pain. The aim of this study is to evaluate the anti-nociceptive effects of synthetic cannabinoids (WIN-55,212 and HU210) and the cannabinoid-like compound palmitoylethanolamide (PEA) in rat models of OA and to assess the role of cannabinoid receptor 1 (CB1) and the peroxisome proliferator-activated receptor α (PPARα) in mediating these effects. Intra-articular injection of monosodium iodoacetate (MIA) in the knee joint was used as a model of osteoarthritis. The von Frey filament test and weight-bearing difference were used to assess the anti-nociceptive effects of WIN-55,212, HU210, and PEA on MIA-induced OA in rats. Open-field locomotor activity system was used confirm the analgesic effects of those compounds. HU210, WIN55, 212, and PEA in a dose-dependent manner restored the paw withdrawal threshold (PWT) and the weight-bearing difference induced by MIA injection. SR141716A (a CB1 antagonist) significantly reversed the anti-nociceptive effects of all the administered drugs in terms of PWT. However, in terms of weight-bearing difference, SR141716A significantly reduced the anti-nociceptive effect of HU210 but not PEA or WIN55, 212. GW6471 (a PPARα antagonist) significantly reversed the anti-nociceptive effects of PEA but not those of HU210 or WIN55, 212. HU210, WIN55, 212 and PEA significantly restored the MIA-induced reduction in locomotor activity. In conclusions, both CB1 and PPARα receptors are involved in mediating pain in osteoarthritis. Therefore, targeting these receptors may be of great clinical value.

Pain is susceptible to various cognitive factors. Suppression of pain by hunger is well known, but the effect of food intake after fasting (i.e. refeeding) on pain remains unknown. In the present study, we examined whether inflammatory pain behavior is affected by 24 h fasting and 2 h refeeding. In formalin-induced acute inflammatory pain model, fasting suppressed pain behavior only in the second phase and the analgesic effect was also observed after refeeding. Furthermore, in Complete Freund's adjuvant-induced chronic inflammatory pain model, both fasting and refeeding reduced spontaneous pain response. Refeeding with non-calorie agar produced an analgesic effect. Besides, intraperitoneal (i.p.) administration of glucose after fasting, which mimics calorie recovery following refeeding, induced analgesic effect. Administration of opioid receptor antagonist (naloxone, i.p.) and cannabinoid receptor antagonist (SR 141716, i.p.) reversed fasting-induced analgesia, but did not affect refeeding-induced analgesia in acute inflammatory pain model. Taken together, our results show that refeeding produce analgesia in inflammatory pain condition, which is associated with eating behavior and calorie recovery effect.

Brain trauma was clinically associated with increased osteogenesis in the appendicular skeleton. We showed previously in C57BL/6J mice that mild traumatic brain injury (mTBI) transiently induced bone formation in the femur via the cannabinoid-1 (CB1) receptor. Here, we subjected ICR mice to mTBI and examined the bone response in the skull using microCT. We also measured mast cell degranulation (MCD)72 h post-injury. Finally, we measured brain and calvarial endocannabinoids levels post-mTBI. mTBI led to decreased bone porosity on the contralateral (untouched) side. This effect was apparent both in young and mature mice. Administration of rimonabant (CB1 inverse agonist) completely abrogated the effect of mTBI on calvarial porosity and significantly reduced MCD, compared with vehicle-treated controls. We also found that mTBI resulted in elevated levels of anandamide, but not 2-arachidonoylglycerol, in the contralateral calvarial bone, whereas brain levels remained unchanged. In C57BL/6J CB1 knockout mice, mTBI did not reduce porosity but in general the porosity was significantly lower than in WT controls. Our findings suggest that mTBI induces a strain-specific CB1-dependent bone anabolic response in the skull, probably mediated by anandamide, but seemingly unrelated to inflammation. The endocannabinoid system is therefore a plausible target in management of bone response following head trauma.

CB1 receptor (CB1R) antagonism improves the deleterious effects of a high-fat diet (HFD) by reducing body fat mass and adipocyte cell size. Previous studies demonstrated that the beneficial effects of the CB1R antagonist rimonabant (RIM) in white adipose tissue (WAT) are partially due to an increase of mitochondria numbers and upregulation thermogenesis markers, suggesting an induction of WAT beiging. However, the molecular mechanism by which CB1R antagonism induces weight loss and WAT beiging is unclear. In this study, we probed for genes associated with beiging and explored longitudinal molecular mechanisms by which the beiging process occurs. HFD dogs received either RIM (HFD+RIM) or placebo (PL) (HFD+PL) for 16 wk. Several genes involved in beiging were increased in HFD+RIM compared with pre-fat, HFD, and HFD+PL. We evaluated lipolysis and its regulators including natriuretic peptide (NP) and its receptors ( NPRs ), β-1 and β-3 adrenergic receptor ( β1R , β3R ) genes. These genes were increased in WAT depots, accompanied by an increase in lipolysis in HFD+RIM. In addition, RIM decreased markers of inflammation and increased adiponectin receptors in WAT. We observed a small but significant increase in UCP1 ; therefore, we evaluated the newly discovered UCP1-independent thermogenesis pathway. We confirmed that SERCA2b and RYR2 , the two key genes involved in this pathway, were upregulated in the WAT. Our data suggest that the upregulation of NPRs , β-1R and β-3R , lipolysis, and SERCA2b and RYR2 may be one of the mechanisms by which RIM promotes beiging and overall the improvement of metabolic homeostasis induced by RIM.

Recent pharmacological findings regarding rimonabant, an anorectic and cannabinoid type 1 receptor (CB1R) antagonist, strongly suggest that some of its effects on the metabolic parameters and energy balance in rats are not related to the centrally mediated reduction in caloric intake. Instead, they may be associated with acute induction of glycogenolysis in the liver, in combination with transient increase in glucose oxidation and persistent increase in fat oxidation. It is possible that rimonabant produced direct short- or long-term stimulatory effect on these processes in primary and cultured rat cells. Rimonabant slightly stimulated β-oxidation of long-chain fatty acids in cultured rat myocytes overexpressing glucose transporter isoform 4, as well as activated phosphorylation of adenosine monophosphate-dependent protein kinase (AMPK) in primary rat hepatocytes upon long-term incubation. However, short-term action of rimonabant failed to stimulate β-oxidation in myocytes, myotubes, and hepatocytes, as well as to upregulate AMPK phosphorylation, glycogenolysis, and cAMP levels in hepatocytes. As a consequence, the acute effects of rimonabant on hepatic glycogen content (reduction) and total energy expenditure (increase) in rats fed with a standard diet cannot be explained by direct stimulation of glycogenolysis and fatty acid oxidation in muscles and liver. Rather, these effects seem to be centrally mediated.

One of most formidable problems in the treatment of addiction is the high rate of relapse. The discovery of medicines to help mitigate relapse are aided by animal models that currently involve weeks of training and require surgical preparations and drug delivery devices. The present set of experiments was initiated to investigate a rapid 8-day screening method that utilizes food instead of intravenous drug administration. Male Sprague-Dawley rats were trained in a reinstatement paradigm in which every lever press produced a 45 mg food pellet concurrently paired with a light and tone. Behavior was subsequently extinguished with lever responses producing neither food nor food-associated stimuli. Reinstatement of responding was evaluated under conditions in which the first three responses of every 5 min time bin produced a food pellet along with food-associated stimuli. The mGlu 5 receptor antagonists MPEP and MTEP produced a significant reduction in reinstatement while failing to alter responding where every response produced food. The cannabinoid CB 1 receptor antagonist rimonabant and the mGlu 2/3 receptor agonist LY379268 also selectively reduced reinstatement. Other compounds including clozapine, d-amphetamine, chlordiazepoxide, ABT-431, naltrexone and citalopram were without effect. The results suggest that relapse-like behavioral effects can be extended to non-pharmacological reinforcers. Drug effects demonstrated both behavioral and pharmacological specificity. The present experimental design thus allows for efficient and rapid assessment of the effects of drugs that might be useful in the treatment of addiction-associated relapse., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Δ 9 -Tetrahydrocannabinol (THC) is known to have various pharmacological effects mediated through activation of cannabinoid CB 1 and CB 2 receptors in rodents. In adult rats, 22- and 50-kHz ultrasonic vocalizations (USVs) serve as an effective communication system and as indicators of negative and positive states, respectively. The present study was performed to determine whether THC affects USVs in adult rats, and to determine the roles of cannabinoid receptors in these effects. THC (1, 3 mg/kg) was administered intraperitoneally to adult male Wistar rats 60 min before measurement of USVs. The CB 1 antagonist, SR141716 (3, 6 mg/kg), or CB 2 antagonist, AM630 (1, 10 mg/kg), was administered intraperitoneally 10 min before THC. USVs were measured during a 5-minute period without air puff stimulus or with air puff stimulus. THC did not affect 22- or 50-kHz USVs without air puff stimulus. On the other hand, THC significantly increased the number of 22-kHz USVs, but not 50-kHz USVs, after air puff stimulus. Moreover, SR141716 at 6 mg/kg, but not AM630 at either dose, inhibited the increase in number of 22-kHz USVs induced by THC after air puff stimulus. These results suggest that THC induced changes in sensitivity to aversive air puff stimuli through CB 1 receptors, and as a result increased emission of 22-kHz USVs in rats., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Although cannabinoid receptor 1 (CB1) antagonists have been shown to attenuate diet-induced obesity (DIO) and associated inflammation, the precise molecular mechanisms involved are not clear. In the current study, we investigated the role of microRNA (miR) in the regulation of adipose tissue macrophage (ATM) phenotype following treatment of DIO mice with the CB1 antagonist SR141716A. DIO mice were fed high-fat diet (HFD) for 12 weeks and then treated daily with SR141716A (10 mg/kg) for 4 weeks while continuing HFD. Treated mice experienced weight loss, persistent reduction in fat mass, improvements in metabolic profile, and decreased adipose inflammation. CB1 blockade resulted in down-regulation of several miRs in ATMs, including the miR-466 family and miR-762. Reduced expression of the miR-466 family led to induction of anti-inflammatory M2 transcription factors KLF4 and STAT6, whereas down-regulation of miR-762 promoted induction of AGAP-2, a negative regulator of the neuroimmune retention cues, Netrin-1 and its coreceptor UNC5B. Furthermore, treatment of primary macrophages with SR141716A up-regulated KLF4 and STAT6, reduced secretion of Netrin-1, and increased migration toward the lymph node chemoattractant CCL19. These studies demonstrate for the first time that CB1 receptor blockade attenuates DIO-associated inflammation through alterations in ATM miR expression that promote M2 ATM polarization and macrophage egress from adipose tissue. The current study also identifies additional novel therapeutic targets for diet-induced obesity and metabolic disorder., (© 2019 Mehrpouya-Bahrami et al.)

The reinforcing effects of Δ 9 -tetrahydrocannabinol (THC) in rats and monkeys, and the reinforcement-related dopamine-releasing effects of THC in rats, can be attenuated by increasing endogenous levels of kynurenic acid (KYNA) through systemic administration of the kynurenine 3-monooxygenase inhibitor, Ro 61-8048. KYNA is a negative allosteric modulator of α7 nicotinic acetylcholine receptors (α7nAChRs) and is synthesized and released by astroglia, which express functional α7nAChRs and cannabinoid CB1 receptors (CB1Rs). Here, we tested whether these presumed KYNA autoreceptors (α7nAChRs) and CB1Rs regulate glutamate release. We used in vivo microdialysis and electrophysiology in rats, RNAscope in situ hybridization in brain slices, and primary culture of rat cortical astrocytes. Acute systemic administration of THC increased extracellular levels of glutamate in the nucleus accumbens shell (NAcS), ventral tegmental area (VTA), and medial prefrontal cortex (mPFC). THC also reduced extracellular levels of KYNA in the NAcS. These THC effects were prevented by administration of Ro 61-8048 or the CB1R antagonist, rimonabant. THC increased the firing activity of glutamatergic pyramidal neurons projecting from the mPFC to the NAcS or to the VTA in vivo. These effects were averted by pretreatment with Ro 61-8048. In vitro, THC elicited glutamate release from cortical astrocytes (on which we demonstrated co-localization of the CB1Rs and α7nAChR mRNAs), and this effect was prevented by KYNA and rimonabant. These results suggest a key role of astrocytes in interactions between the endocannabinoid system, kynurenine pathway, and glutamatergic neurotransmission, with ramifications for the pathophysiology and treatment of psychiatric and neurodegenerative diseases.

We performed a comparative study of the cytotoxic effect of endocannabinoid N-arachidonoyl dopamine (AA-DA) on cultured stromal cells of ectopic and eutopic endometrium. It was found that AA-DA in the concentration range of 1-20 μM produces more selective cytotoxic effect on the stromal cells of the ectopic endometrium due to interaction with cannabinoid type 1 receptor. In concentrations below 1 μM, AA-DA stimulated the proliferation of stromal cells of the eutopic endometrium and did not affect the division of ectopic endometrium cells. This effect was realized due to its interaction with cannabinoid type 2 receptor.

Intellectual disability is the most limiting hallmark of Down syndrome, for which there is no gold-standard clinical treatment yet. The endocannabinoid system is a widespread neuromodulatory system involved in multiple functions including learning and memory processes. Alterations of this system contribute to the pathogenesis of several neurological and neurodevelopmental disorders. However, the involvement of the endocannabinoid system in the pathogenesis of Down syndrome has not been explored before. We used the best-characterized preclinical model of Down syndrome, the segmentally trisomic Ts65Dn model. In male Ts65Dn mice, cannabinoid type-1 receptor (CB1R) expression was enhanced and its function increased in hippocampal excitatory terminals. Knockdown of CB1R in the hippocampus of male Ts65Dn mice restored hippocampal-dependent memory. Concomitant with this result, pharmacological inhibition of CB1R restored memory deficits, hippocampal synaptic plasticity and adult neurogenesis in the subgranular zone of the dentate gyrus. Notably, the blockade of CB1R also normalized hippocampal-dependent memory in female Ts65Dn mice. To further investigate the mechanisms involved, we used a second transgenic mouse model overexpressing a single gene candidate for Down syndrome cognitive phenotypes, the dual specificity tyrosine-phosphorylation-regulated kinase 1A (DYRK1A). CB1R pharmacological blockade similarly improved cognitive performance, synaptic plasticity and neurogenesis in transgenic male Dyrk1A mice. Our results identify CB1R as a novel druggable target potentially relevant for the improvement of cognitive deficits associated with Down syndrome., (Copyright © 2019 Elsevier Inc. All rights reserved.)

The taste of sucrose is commonly used to provide pain relief in newborn humans and is innately analgesic to neonatal rodents. In adulthood, sucrose remains a strong motivator to feed, even in potentially hazardous circumstances (ie, threat of tissue damage). However, the neurobiological mechanisms of this endogenous reward-pain interaction are unclear. We have developed a simple model of sucrose drinking-induced analgesia in Sprague-Dawley rats (6-10 weeks old) and have undertaken a behavioral and pharmacological characterization using the Hargreaves' test of hind-paw thermal sensitivity. Our results reveal an acute, potent, and robust inhibitory effect of sucrose drinking on thermal nociceptive behaviour that unlike the phenomenon in neonates is independent of endogenous opioid signalling and does not seem to operate through classical descending inhibition of the spinal cord circuitry. Experience of sucrose drinking had a conditioning effect whereby the apparent expectancy of sucrose enabled water alone (in euvolemic animals) to elicit a short-lasting placebo-like analgesia. Sweet taste alone, however, was insufficient to elicit analgesia in adult rats intraorally perfused with sucrose. Instead, the sucrose analgesia phenomenon only appeared after conditioning by oral perfusion in chronically cannulated animals. This sucrose analgesia was completely prevented by systemic dosing of the endocannabinoid CB1 receptor antagonist rimonabant. These results indicate the presence of an endogenous supraspinal analgesic circuit that is recruited by the context of rewarding drinking and is dependent on endocannabinoid signalling. We propose that this hedonic sucrose-drinking model may be useful for further investigation of the supraspinal control of pain by appetite and reward.

Repeated exposure to life stressors can overwhelm the body's capacity to restore homeostasis and result in severe negative consequences. Cannabinoid CB 1 receptors are highly expressed in the Central Nervous System (CNS) and regulate both glucocorticoid signalling and neurotransmitter release. In rodents, WIN55212.2 is a full agonist at the cannabinoid receptor type-1, while Rimonabant is a potent and selective cannabinoid inverse agonist at this receptor. This study aims to investigate the effect of long-term psychosocial stress following acute challenge with cannabinoid drugs on gene expression in distinct brain regions; this is done by employing digital multiplexed gene expression analysis. We found that repeated stress increased cortical mRNA levels of dopamine receptor D2, while the expression of neuregulin-1 decreased in both the prefrontal cortex and cerebellum. Further, we found that the acute injection of the agonist WIN55212.2 reduced striatal levels of dopamine receptor D2, while the use of inverse agonist Rimonabant acted in the opposite direction. The analysis of the interaction between the drugs and repeated stress revealed that defeat mice treated with WIN55212.2 showed lower expression of a set of myelin-related genes, as did the expression of SRY-box 10 and dopamine receptors-D1 and -D2 in the prefrontal cortex when compared to vehicle. In addition, in the hippocampus of stressed mice treated with WIN55212.2, we found an elevated expression of oligodendrocyte transcription factor-1, -2 and zinc finger protein 488 when compared to vehicle. In comparison to vehicle, an increase in 2',3'-Cyclic nucleotide 3'-phosphodiesterase and oligodendrocyte transcription factor-1 occurred in the cerebellum of stressed animals treated with the agonist. Moreover, treatment with Rimonabant under the influence of stress induced an overexpression of a set of myelin-related genes in the prefrontal cortex when compared to WIN-treated animals. In conclusion, repeated stress interfered with the dopaminergic system in the prefrontal cortex. We demonstrated that the expression of dopamine receptor D2 in the striatum was mediated by the CB 1 receptor. Stressed mice exposed to either WIN55212.2 or Rimonabant displayed pronounced deficits in CNS myelination. In addition, the pharmacological blockage of CB 1 receptor in stressed mice deregulated the expression of dopamine receptors and might lead to dysfunctions in dopamine metabolism., (Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Sepsis is a life-threatening condition with high mortality rates that is caused by dysregulation of the host response to infection. We previously showed that treatment with the cannabinoid CB 1 receptor antagonist rimonabant reduced mortality rates in animals with sepsis that was induced by cecal ligation and puncture (CLP). This improvement in the survival rate appeared to be related to an increase in arginine vasopressin (AVP) levels 12 h after CLP. The present study investigated the effects of rimonabant on organ dysfunction, hematologic parameters, and vascular reactivity in male Wistar rats with sepsis induced by CLP. Intraperitoneal treatment with rimonabant (10 mg/kg, 4 h after CLP) abolished the increase in the plasma levels of lactate, lactate dehydrogenase, glucose, and creatinine kinase MB without altering hematological parameters (i.e., leukopenia and a reduction of platelet counts). CLP increased plasma levels of nitrate/nitrite (NOx) and induced vasoconstriction in the tail artery. The treatment of CLP rats with rimonabant did not alter NOx production but reduced the vasoconstriction. Rimonabant also attenuated the hyperreactivity to AVP induced by CLP without affecting hyporesponsiveness to phenylephrine in aortic rings. These results suggest that rimonabant reduces organ dysfunction during sepsis, and this effect may be related to AVP signaling in blood vessels. This effect may have contributed to the higher survival rate in rimonabant-treated septic animals.

Cannabis withdrawal upon discontinuation of long-term, heavy Cannabis use is reported in humans; however, methods to establish the nature and intensity of cannabinoid withdrawal, especially directly observable signs, have not been widely established. This study quantified activity in the home cage of rhesus monkeys and examined the extent to which activity can be used to quantify tolerance to and dependence on Δ9-tetrahydrocannabinol (Δ9-THC). Home-cage activity was measured in one group that received Δ9-THC (1 mg/kg s.c.) every 12 h (i.e., chronic Δ9-THC), and a second group that received Δ9-THC (0.1 mg/kg i.v.) once every 3 days (i.e., intermittent Δ9-THC). Treatment was temporarily discontinued in the chronic Δ9-THC group and the effects of rimonabant and Δ9-THC were examined in both groups. Activity counts were highest during the day (lights on 0600-2000 h) and were lower at night. Rimonabant (0.1-3.2 mg/kg i.v.) dose-dependently increased activity (maximum 20-fold) in the chronic Δ9-THC group but did not significantly alter activity in the intermittent Δ9-THC group. Δ9-THC (0.32-3.2 mg/kg i.v.) dose-dependently decreased activity counts (maximum 4-fold) in both groups but was somewhat more potent in the intermittent as compared with the Δ9-THC group. Discontinuation of Δ9-THC treatment resulted in an immediate (i.e., within 24 h) and time-related increase in activity. The time-related increase in home-cage activity upon abrupt discontinuation of chronic Δ9-THC treatment, as well as the effects of rimonabant to increase activity in monkeys receiving chronic, but not intermittent, Δ9-THC treatment, are consistent with signs of physical dependence on Δ9-THC in primates., Competing Interests: The authors have declared that no competing interests exist.

Cannabinoid CB 1 receptors (CB 1 Rs) have been shown to be a promising target in medication development for the treatment of addiction. However, clinical trials with SR141716A (rimonabant, a selective CB 1 R antagonist/inverse agonist) for the treatment of obesity and smoking cessation failed due to unwanted side effects, such as depression, anxiety, and suicidal tendencies. Recent preclinical studies suggest that the neutral CB 1 R antagonist AM4113 may retain the therapeutic anti-addictive effects of SR141716A in nicotine self-administration models and possibly has fewer unwanted side effects. However, little is known about whether AM4113 is also effective for other drugs of abuse, such as opioids and psychostimulants, and whether it produces depressive side effects similar to SR141716A in experimental animals. In this study, we demonstrated that systemic administration of AM4113 (3 and 10 mg/kg) dose-dependently inhibited the self-administration of intravenous heroin but not cocaine or methamphetamine, whereas SR141716A (3 and 10 mg/kg) dose-dependently inhibited the self-administration of heroin and methamphetamine but not cocaine. In the electrical brain-stimulation reward (BSR) paradigm, SR141716A (3 and 10 mg/kg) dose-dependently increased the BSR stimulation threshold (i.e., decreased the stimulation reward), but AM4113 had no effect on BSR at the same doses, suggesting that SR141716A may produce aversive effects while AM4113 may not. Together, these findings show that neutral CB 1 R antagonists such as AM4113 deserve further research as a new class of CB 1 R-based medications for the treatment of opioid addiction without SR141716A-like aversive effects.

Despite the apparent abundance of ligand-gated transient receptor potential vanilloid type 1 (TRPV1) and possible cross talk between the endocannabinoid and endovanilloid systems in the central nervous system (CNS), it is unclear what role TRPV1 receptor activation in CNS plays in neurobehavioral development. We previously reported that capsaicin or WIN55212-2 induces risk aversion in the plus-maze test, which was dependent on the gender and mouse strain used. In this study, pregnant BALBc mice were administered capsaicin (1.0 or 4.0 mg/kg, i.p.) during the second week of gestation. Developmental effects of prenatal exposure to capsaicin were assessed in neonates, and behavioral effects were assessed in adult offspring. Gender- and dose-specific variations in ultrasonic vocalizations, weight gain, righting reflex, and general activity of the pups were observed. Prenatal exposure to capsaicin altered plus-maze performance, especially with further exogenous capsaicin challenge. Furthermore, dose- and gender-specific effects were evident in the conditioned place preference/aversion paradigm following conditioning with capsaicin in adult animals. The capsaicin-induced aversion in the plus-maze test was enhanced by WIN55212-2 and blocked by pretreatment with vanilloid antagonist capsazepine or the CB 1 receptor antagonist rimonabant, demonstrating an interaction between the endocannabinoid and endovanilloid systems in CNS. Taken together, the interaction between the endocannabinoid and endovanilloid signaling systems can be exploited for therapeutic applications in health and disease.

Circulating levels of bacterial lipopolysaccharide (LPS) or endotoxin are chronically elevated in obesity (metabolic endotoxemia), resulting in low-grade inflammation. Metabolic endotoxemia has been identified as a triggering factor for obesity-associated metabolic complications such as insulin resistance. Furthermore, LPS has been shown to modulate endocannabinoid synthesis and notably to induce cannabinoid receptor type-1 (CB1) ligand synthesis. CB1 activation promotes inflammation, increases food intake and impairs insulin signaling. Therefore, we hypothesized that LPS acts through a CB1-dependent mechanism to aggravate inflammation and promote insulin resistance. Male Wistar rats fed a chow diet were implanted with mini-osmotic pumps delivering a low dose of LPS (n = 20; 12.5 μg/kg body weight (BW)/hr.) or saline (n = 10) continuously for six weeks. LPS-treated rats were injected daily with a CB1 antagonist (Rimonabant, SR141716A; 3 mg/kg, intraperitoneal (ip); LPS + CB1x; n = 10) or vehicle (1 mL/kg, LPS; n = 10). Control and LPS rats' food intake was matched to the LPS + CB1x group level. Despite no significant differences in body weight among groups, chronic exposure to low-level LPS altered hepatic endocannabinoid signaling, increased inflammation, and impaired insulin sensitivity and insulin clearance (P < 0.05). CB1 inhibition significantly attenuated LPS signaling (P < 0.05), which attenuated LPS-induced metabolic alterations. Therefore, we concluded that CB1 contributes to LPS-mediated inflammation and insulin resistance, suggesting that blocking CB1 signaling may have therapeutic benefits in reducing inflammation-induced metabolic abnormalities., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Recently, multiple compounds have been synthesized that target the allosteric binding site(s) of CB 1. These CB 1 positive allosteric modulators may capture the benefits of cannabinoid receptor activation without unwanted psychoactive effects, such as sedation. For example, ZCZ011 blocks neuropathic pain, absent the catalepsy, sedation, and hypothermia caused by CB 1 orthosteric modulators, including Δ 9 -tetrahydrocannabinol (THC). The primary goal of the present study was to evaluate the potential of ZCZ011 to attenuate somatic signs of cannabinoid withdrawal in mice. Mice were repeatedly administered THC (10 mg/kg, s.c.) or vehicle, and withdrawal was either precipitated using the CB 1 antagonist rimonabant (3 mg/kg, i.p.) or elicited spontaneously via THC abstinence. ZCZ011 (≥10 mg/kg, i.p.) significantly attenuated somatic signs of withdrawal, including head twitches and paw tremors, but had no effect on locomotor activity or conditioned place preference. We next tested the antiulcerogenic properties of CB 1 positive allosteric modulation. Mice were fasted for 22 h, administered ZCZ011, and gastric hemorrhages were induced with the nonsteroidal anti-inflammatory drug diclofenac sodium (100 mg/kg, p.o.). ZCZ011 alone had no effect on gastric ulceration, but ZCZ011 (≥10 mg/kg) blocked ulcer formation when combined with a subthreshold MAGL inhibitor (JZL184; 1 mg/kg, i.p.). Thus, CB 1 positive allosteric modulation is a novel approach to treat cannabinoid dependence and gastric inflammation., (Copyright © 2018 Elsevier Inc. All rights reserved.)

In high-fat diet (HFD) induced nonalcoholic fatty liver disease (NAFLD), there is an increase in the endocannabinoid system activity, which significantly contributes to steatosis development. The aim of our study was to investigate the effects of cannabinoid receptor type 1 blockade on adipokine and proinflammatory cytokine content in adipose and hepatic tissue in mice with NAFLD. Male mice C57BL/6 were divided into a control group fed with a control diet for 20 weeks (C, n = 6) a group fed with a HFD for 20 weeks (HF, n = 6), a group fed with a control diet and treated with rimonabant after 18 weeks (R, n = 9), and a group fed with HFD and treated with rimonabant after 18 weeks (HFR, n = 10). Rimonabant significantly decreased leptin, resistin, apelin, visfatin, interleukin 6 (IL-6), and interferon-γ (IFN-γ) concentration in subcutaneous and visceral adipose tissue in the HFR group compared to the HF group (p < 0.01). Rimonabant reduced hepatic IL-6 and IFN-γ concentration as well as plasma glucose and insulin concentration and the homeostatic model assessment index in the HFR group compared to the HF group (p < 0.01). It can be concluded that the potential usefulness of CB1 blockade in the treatment of HFD-induced NAFLD is due to modulation of the adipokine profile and proinflammatory cytokines in both adipose tissues and liver as well as glucose metabolism.

Background: Formation of schistosomal granulomata surrounding the ova can result in schistosomiasis-associated liver fibrosis (SSLF). The current standard of treatment is praziquantel (PZQ), which cannot effectively reverse SSLF. The role of the cannabinoid (CB) receptor family in liver fibrosis has recently been highlighted., Objectives: This study aimed to assess the therapeutic effect of CB1 receptor antagonism in reversing SSLF in a murine model of Schistosoma mansoni infection., Methods: One hundred male Swiss albino mice were divided equally into five groups: healthy uninfected control (group I), infected control (group II), PZQ treated (group III), rimonabant (RIM) (SR141716, a CB1 receptor antagonist)-treated (group IV) and group V was treated with combined PZQ and RIM. Liver sections were obtained for histopathological examination, alpha-1 smooth muscle actin (α-SMA) immunostaining and assessment of CB1 receptor expression using real-time polymerase chain reaction (RT-PCR)., Findings: The most effective reduction in fibrotic marker levels and granuloma load was achieved by combined treatment with PZQ+RIM (group V): CB1 receptor expression (H = 26.612, p < 0.001), number of α-SMA-positive cells (F = 57.086, p < 0.001), % hepatic portal fibrosis (F = 42.849, p < 0.001) and number of granulomata (F = 69.088, p < 0.001)., Main Conclusions: Combining PZQ with CB1 receptor antagonists yielded the best results in reversing SSLF. To our knowledge, this is the first study to test this regimen in S. mansoni infection.

Background: The recent NIH mandate to consider sex as a biological variable in preclinical research has focused attention on delineation of sex differences in behavior. To investigate mechanisms underlying sex differences in Δ 9 -tetrahydrocannabinol (THC) effects, we examined the effects of sex and gonadal hormones on CB 1 receptors in cerebellum, hippocampus, prefrontal cortex, and striatum., Methods: Adult Sprague-Dawley rats underwent gonadectomy (GDX) or sham-GDX. Half of the GDX females and males received estradiol or testosterone replacement (GDX+H), respectively. All rats were injected with vehicle or 30 mg/kg THC twice daily for 1 week before brain collection. CP55,940-stimulated [ 35 S]GTPγS and [ 3 H]SR141716A saturation binding assays were performed., Results: With exception of enhanced receptor activation in the hippocampi of female rats compared to males, vehicle-treated rats exhibited minimal sex differences in CB 1 receptor densities or G-protein coupling. Repeated treatment with THC resulted in pronounced CB 1 receptor desensitization and downregulation in both sexes in all brain regions with a greater magnitude of change in females., Conclusions: These results suggest that sex differences in the density and G-protein coupling of brain CB 1 receptors may play a limited role in sex differences in acute THC effects not mediated by the hippocampus. In contrast, sex differences after repeated THC were common, with females (intact, GDX, and GDX+H) showing greater downregulation or desensitization in all four brain regions compared to the respective male groups. This result is consistent with a finding that women tend to progress to tolerance and dependence quicker than men after initiation of cannabis use., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Cannabinoid receptor 1 (CB 1 ) is a G-protein-coupled receptor that is abundant in the central nervous system. It binds several compounds in its orthosteric site, including the endocannabinoids, arachidonoyl ethanolamide (anandamide) and 2-arachidonoyl glycerol, and the plant-derived Δ 9 -tetrahydrocannabinol, one of the main psychoactive components of marijuana. It primarily couples to G i/o proteins to inhibit adenylate cyclase activity and typically induces downstream signaling that is G i -dependent. Since this receptor is implicated in several maladies, such as obesity, pain, and neurodegenerative disorders, there is interest in developing therapeutics that selectively target this receptor. Allosteric modulators of CB 1 offer one new approach that has tremendous therapeutic potential. Here, we reveal receptor- and cellular-level properties consistent with receptor activation by a series of pyrimidinyl biphenylureas (LDK1285, LDK1288, LDK1305, and PSNCBAM1), including promoting binding of the agonist CP55940 with positive cooperativity and inhibiting binding of the inverse agonist SR141716A with negative cooperativity, demonstrated via radioligand binding studies. Consistent with these findings, the allosteric modulators induced cellular internalization of the receptor and recruitment of β -arrestin 2 in human embryonic kidney cell line 293 cells monitored with confocal and total internal reflective fluorescence microscopy, respectively. These allosteric modulators, however, caused G-protein-independent but β -arrestin 1-dependent phosphorylation of the downstream kinases extracellular signal-regulated kinase 1/2, mitogen-activated protein kinase, and Src, shown by immunoblotting studies. These results are consistent with the involvement of β -arrestin and suggest that these allosteric modulators induce biased signaling., (Copyright © 2018 by The American Society for Pharmacology and Experimental Therapeutics.)

The cannabinoid CB1 receptor is expressed throughout the central nervous system where it functions to regulate neurotransmitter release and synaptic plasticity. While the CB1 receptor has been identified as a target for both natural and synthetic cannabinoids, the specific downstream signaling pathways activated by these various ligands have not been fully described. In this study, we developed a real-time membrane potential fluorescent assay for cannabinoids using pituitary AtT20 cells that endogenously express G protein-gated inward rectifier K + (GIRK) channels and were stably transfected with the CB1 receptor using a recombinant lentivirus. In whole-cell patch clamp experiments application of the cannabinoid agonist WIN 55,212-2 to AtT20 cells expressing the CB1 receptor (AtT20/CB1) activated GIRK currents that were blocked by BaCl 2 . WIN 55,212-2 activation of the GIRK channels was associated with a time- and concentration-dependent (EC 50  = 309 nM) hyperpolarization of the membrane potential in the AtT20/CB1 cells when monitored using a fluorescent membrane potential-sensitive dye. The WIN 55,212-2-induced fluorescent signal was inhibited by pretreatment of the cells with either the GIRK channel blocker tertiapin-Q or the CB1 receptor antagonist SR141716. The cannabinoids displayed a response of WIN 55,212-2 ≈ anandamide (AEA) > CP 55,940 > Δ 9 -tetrahydrocannabinol (THC) when maximal concentrations of the four ligands were tested in the assay. Thus, the AtT20/CB1 cell fluorescent assay will provide a straightforward and efficient methodology for examining cannabinoid-stimulated G i signaling., (Copyright © 2018 Elsevier Inc. All rights reserved.)