CB1 Receptor Antagonist Rimonabant Research Articles

N-eicosapentaenoyl-ethanolamine decreases the proliferation of psoriatic keratinocytes in a reconstructed psoriatic skin model

Psoriasis is an inflammatory skin disease that is characterized by keratinocyte hyperproliferation, abnormal epidermal differentiation and dysregulated lipid metabolism. Some lipid mediators of the N-acylethanolamines (NAEs) and monoacylglycerols (MAGs) can bind to cannabinoid (CB) receptors and are referred to as part of the endocannabinoidome. Their implication in psoriasis remains unknown. The aim of the present study was to characterize the endocannabinoid system and evaluate the effects of n-3-derived NAEs, namely N-eicosapentaenoyl-ethanolamine (EPEA), in psoriatic keratinocytes using a psoriatic skin model produced by tissue engineering, following the self-assembly method. Psoriatic skin substitutes had lower FAAH2 expression and higher MAGL, ABHD6 and ABHD12 expression compared with healthy skin substitutes. Treatments with alpha-linolenic acid (ALA) increased the levels of EPEA and 1/2-docosapentaenoyl-glycerol, showing that levels of n-3 polyunsaturated fatty acids modulate related NAE and MAG levels. Treatments of the psoriatic substitutes with 10 μM of EPEA for 7 days resulted in decreased epidermal thickness and number of Ki67 positive keratinocytes, both indicating decreased proliferation of psoriatic keratinocytes. EPEA effects on keratinocyte proliferation were inhibited by the CB1 receptor antagonist rimonabant. Exogenous EPEA also diminished some inflammatory features of psoriasis. In summary, n-3-derived NAEs can reduce the psoriatic phenotype of a reconstructed psoriatic skin model.

Context-dependent effects of the CB1 receptor antagonist rimonabant on morphine-induced behavioral sensitization in female mice.

Introduction: The endocannabinoid system has been implicated in the neurobiology of opioid use disorder. While the CB1 receptor antagonist rimonabant has been shown to block some of the behavioral effects of opioids, studies suggest that the treatment environment (i.e., receiving treatment in the drug-associated environment, and/or novelty) can influence its effects. In the present study, we investigated the role of the treatment environment in the effects of rimonabant on the expression of morphine-induced behavioral sensitization. Methods: Adult female Swiss mice were submitted to a behavioral sensitization protocol, during which they received morphine (20mg/kg, i.p.) in the open-field apparatus, and were subsequently treated with vehicle or rimonabant (1 or 10mg/kg, i.p.) either in the open-field, in the home-cage or in an activity box (novel environment). The expression of conditioned locomotion (increased locomotor activity in the open-field apparatus in the absence of morphine) and of morphine-induced behavioral sensitization (increased locomotor activity in animals sensitized to morphine) was evaluated during asubsequent saline and morphine challenge, respectively. Results: Animals treated with morphine expressed behavioral sensitization, showing a significant increase in locomotor activity over time. Animals sensitized to morphine and treated with vehicle in the home-cage expressed conditioned locomotion, an effect that was blocked by home-cage treatment with rimonabant. During a saline challenge, only animals sensitized to morphine and treated with saline in the home-cage expressed morphine-induced conditioned locomotion. All morphine-treated animals that received saline during the treatment phase (control groups) expressed behavioral sensitization during the morphine challenge. Treatment with rimonabant in the open-field and in the activity box, but not in the home-cage, blocked the expression of morphine-induced behavioral sensitization. Discussion: Our findings suggest that CB1 receptor antagonism can modulate conditioned responses to morphine even when administered in the home-cage. However, exposure to the drug-associated environment or to a novel environment is necessary for the expression of rimonabant's effects on morphine-induced behavioral sensitization during a morphine challenge.

CB1 receptor antagonist rimonabant protects against chronic intermittent hypoxia-induced renal injury in rats

BackgroundObstructive sleep apnoea (OSA) induced chronic kidney disease is mainly caused by chronic intermittent hypoxia (CIH). Our study investigate the mechanism underlying CIH-induced renal damage and whether the cannabinoid receptor 1 (CB1R) antagonist rimonabant (Ri) alleviates CIH-induced renal injury.MethodsMale Sprague-Dawley rats were randomly divided into five groups: one normal control (NC) group, two chronic intermittent hypoxia (CIH) groups, and two CIH + Ri groups. Rats in the NC groups were exposed to room air, while the CIH groups were exposed to a CIH environment for 4 weeks (4w CIH group) and 6 weeks (6w CIH group), respectively. Additionally, rats in the CIH + Ri groups were administered 1.5 mg/kg/day Ri for 4 weeks (4w CIH + Ri group) and 6 weeks (6w CIH + Ri group), respectively. Following this, the rats were euthanized and kidneys were excised for downstream analysis. In the renal tissues, the morphological alterations were examined via haematoxylin eosin (HE) staining and periodic acid schiff (PAS) staining, CB1R, Fis1, Mfn1, and p66Shc expression was assessed through western blot and immunohistochemistry, and the mitochondrial ultrastructural changes in kidney sections were assessed by electron microscopy.ResultsCB1R expression in the 4w and 6w CIH groups was significantly elevated, and further increased with prolonged hypoxia; however, Ri prevented the increase in CIH-induced CB1R expression. Fis1 and p66Shc expression in the CIH groups were increased, but Mfn1 expression decreased. Ri decreased Fis1 and p66Shc expression and increased Mfn1 expression. Renal damage in the 4w or 6w CIH + Ri group was evidently improved compared with that in the 4w or 6w CIH group. CB1R expression was positively correlated with Fis1 and p66Shc and negatively correlated with Mfn1. Meanwhile, electron microscopy showed that the percentage of fragmented mitochondria in the tubular cells in each group was consistent with the trend of CB1R expression.ConclusionCIH causes endocannabinoid disorders and induces abnormal mitochondrial dynamics, resulting in renal injury. Treatment with CB1R antagonists reduces CIH-induced renal damage by inhibiting dysregulated renal mitochondrial dynamics.

Receptor mechanism of infarct-limiting effect of adaptation to normobaric hypoxia

The aim of the study was to investigate the involvement of bradykinin, cannabinoid and vanilloid (TRPV1 channel) receptors in the implementation of the infarct-limiting effect of chronic normobaric hypoxia (CNH). Materials and methods . The study was performed on male Wistar rats ( n = 117) weighing 250–300 g. Adaptation to CNH was modeled for 21 days at 12% pO 2 , 0.3% pCO 2 and normal atmospheric pressure. A day after adaptation of rats to CNH coronary artery occlusion (45 min) and reperfusion (2 h) was performed. In the study the following compounds were used: selective cannabinoid CB1 receptor antagonist rimonabant (1 mg/kg), selective cannabinoid CB2 receptor antagonist AM630 (2.5 mg/kg), selective bradykinin B2 receptor antagonist HOE140 (50 μg/kg), and vanilloid receptor (TRPV1 channel) antagonist capsazepine (3 mg/kg). All antagonists were administered 15 min before coronary artery occlusion. Results. Adaptation to normobaric hypoxia promoted the formation of the pronounced infarct-limiting effect. The blockade of B2 receptor eliminated the infarct-limiting effect of CNH. Blockade of cannabinoid or vanilloid receptors did not affect the infarct-limiting effect of CNH. Conclusion . The infarct-limiting effect of CNH depends on the activation of B2 receptor, and the adaptive increase in cardiac tolerance to ischemia/reperfusion does not depend on cannabinoid or vanilloid receptors.

S3427 Cannabis in Relation to Gastroesophageal Reflux Disease

INTRODUCTION: There is a wide distribution of cannabinoid receptors (CBR) in the enteric nervous system, highlighting the role of cannabis in GI health and disease. Of these, CB1 is most often expressed and has been shown to decrease intra-gastric pressure, affect transient LES relaxation (TLESR), and concurrently delay gastric emptying via inhibition of excitatory neurons. We compared three different articles on their studies of cannabinoid receptors in relation to the upper GI tract. The goal of this systematic review is to assess the current knowledge of cannabis implementation, effectiveness, and its adverse side effects, in addition to identifying areas for expanding research. CASE DESCRIPTION/METHODS: In a study conducted by Calabrese et al, 87 total subjects consisting of 10 controls, 39 with non-erosive esophageal reflux (NERD), and 38 with erosive esophageal reflux (ERD) who had typical symptoms for >1 year had eight specimens of macroscopically normal esophageal mucosa taken and analyzed for expression of CBRs. Beaumont et al assessed the response of 10 mg and 20 mg Δ9-THC, a cannabinoid agonist, given three doses each a week apart in healthy volunteers. LES pressure, spontaneous swallows, and reflux episodes were measured. Scarpenllini et al studied the effects of a CB1 receptor antagonist Rimonabant on fasting and postprandial LES function in healthy subjects. Twelve healthy volunteers underwent esophageal manometry studies with administration of wet swallows and a meal after 3 days of premedication with placebo or 20 mg of Rimonabant. Transient LES relaxations and reflux episodes were measured. DISCUSSION: There is a need for more research to be performed, not only on the effects of THC on the GI system, but also for dosing to determine whether or not cannabis can be used as a therapy for esophageal disorders. With increased regulation of cannabis products and further research, consumers would be able to reduce the risks of experiencing unpleasant side effects. It is important to note that cannabis use can also lead to complications, including cannabinoid hyperemesis syndrome. No definitive recommendations can be made at this time on whether or not cannabis use will be a useful therapy for GI disorders until more research is completed.

Effects of the Endocannabinoid Anandamide on the Efficiency of Noradrenergic Neurotransmission in the Amygdaloid Body in Acute Stress in Mice

The effects of endocannabinoid neurotransmission on corticosterone secretion by the adrenals and release of noradrenaline in the amygdaloid body during acute stress modeled in the elevated platform test were studied by intracerebral microdialysis in C57Bl/6N mice using the CB1 receptor antagonist rimonabant and the anandamide reuptake inhibitor AM-404. Increases in corticosterone secretion on exposure to rimonabant (3 mg/kg, p.o.) confi rmed the role of CB1 receptors in controlling the activity of the hypothalamo-hypophyseal-adrenal (HHA) system and verifi ed their infl uences on the amplitude but not the duration of hormone secretion. Stress was accompanied by a transient increase in noradrenaline release in the amygdaloid body. AM-404 (3 mg/kg, i.p.) suppressed but did not fully inhibit stress-induced noradrenaline release, decreasing it to control levels. The results obtained here provide evidence that the endocannabinoid anandamide is involved in regulating presynaptic noradrenaline release in the amygdaloid body in conditions of psychological stress.

CB1 receptor antagonist rimonabant protects against chronic intermittent hypoxia-induced bone metabolism disorder and destruction in rats

ObjectiveThe endocannabinoid system (ECS) regulates bone turn-over and remodeling. Chronic intermittent hypoxia (CIH) occurring during obstructive sleep apnea (OSA) may lead to disorders of the ECS and bone metabolism abnormalities. This study aimed to investigate whether or not the cannabinoid receptor 1 (CB1R) antagonist rimonabant (Ri) alleviates bone metabolism abnormalities and bone destruction induced by chronic intermittent hypoxia (CIH). MethodsHealthy male Sprague Dawley (SD) rats (n=48) were randomly divided into 6 groups of 8 rats: 2 normal control (NC) groups, 2 intermittent hypoxia (IH) groups, and 2 IH + Ri groups. Rats in NC groups breathed room air for 4 weeks (4w NC group) and 6 weeks (6w NC group). Rats in IH groups experienced IH environment for 4 weeks (4w IH group) and 6 weeks (6w IH group). In addition to the same IH exposure, rats in IH + Ri group were given daily intraperitoneal injection of Ri at the dosage of 1.5 mg/kg/d for 4 weeks (4w IH + Ri group) and 6 weeks (6w IH + Ri group). Levels of serum tartrate-resistant acid phosphatase (TRAP, a marker of bone resorption) were determined by ELISA. Hematoxylin and eosin (HE) staining was performed on bone sections to observe the changes in bone microstructure. Expression of CB1R in bone tissue was determined by immunohistochemistry. ResultsTRAP levels were higher in the 4w IH and 6w IH groups than in the 4w NC and 6w NC groups; TRAP levels were lower in the 4w IH + Ri and 6w IH + Ri groups than in the 4w IH and 6w IH groups. HE staining showed that the morphology of bone cells in the NC group was normal, but the 4w IH group had mild edema of bone cells, reduction in trabecular bone, and destruction of bone microstructure. Changes were more severe in the 6w IH group than 4w IH. The 4w IH + Ri group was slightly improved compared with the 4w IH group. The 6w IH + Ri group was improved compared with the 4w IH + Ri group. The results of immunohistochemistry showed that the expression of CB1R in IH group was significantly higher than that in NC group. The expression of CB1R in the IH + Ri group was lower than that in the IH group. With the prolongation of hypoxia, the expression of CB1R in bone cells of IH group increased. The expression level of CB1R in IH + Ri group decreased with the prolongation of intervention time. Correlation analysis showed that the expression rate of CB1R in bone cells was positively correlated with the level of TRAP in serum.ConclusionCIH increases serum TRAP levels and triggers metabolic bone disorder by activating bone CB1R. Intervention with CB1R antagonist (rimonabant) reduces the bone dysmetabolism in the CIH rat model.

CB1 receptor antagonist rimonabant protects against chronic intermittent hypoxia-induced bone metabolism disorder and destruction in rats

CB1 receptor antagonist rimonabant protects against chronic intermittent hypoxia-induced bone metabolism disorder and destruction in rats

Pharmacokinetic and Pharmacodynamic Characterization of Tetrahydrocannabinol-Induced Cannabinoid Dependence After Chronic Passive Cannabis Smoke Exposure in Rats.

Introduction: Cannabis is the most widely used illicit drug in the US, and cannabis use among young adults continues to rise. Previous studies have shown that chronic administration of delta 9-tetrahydrocannabinol (THC), the main psychoactive component of cannabis, induces dependence in animal models. Because smoking is the most frequent route of THC self-administration, it is critical to investigate the effects of cannabis smoke inhalation. The goal of the current study was to develop a rat model to characterize the pharmacokinetics (PKs) of THC after cannabis smoke inhalation, and to determine if chronic cannabis smoke inhalation leads to the development of cannabis dependence. Materials and Methods: For the PK study, male Wistar rats were administered THC intravenously (1 mg/kg) or exposed to smoke from 5 or 10 sequentially smoked cannabis cigarettes (5.3% THC) in an automated smoking machine. Plasma samples were collected from 10 min to 10 hours post smoke exposure (or intravenous administration) and analyzed using liquid chromatography-mass spectrometry to characterize the PK of THC. A three-compartment PK model was used to characterize the PKs. In a separate study, three groups of male Wistar rats were trained in an intracranial self-stimulation (ICSS) procedure, and exposed to smoke from burning 5 or 10 cannabis cigarettes (or clean air control conditions), 5 days/week for 4 weeks. Discussion and Conclusions: Across exposure days, the change from baseline in ICSS thresholds for cannabis smoke-exposed groups was significantly lower and response latencies were significantly faster in the cannabis smoke-exposed groups compared to controls, suggesting that chronic cannabis smoke exposure has rewarding properties. Acute administration of the CB1 receptor antagonist rimonabant (0.3, 1.0, 3.0 mg/kg) induced a dose-dependent increase in ICSS thresholds in the smoke-exposed rats, suggestive of dependence and withdrawal. Finally, an effect compartment PK-pharmacodynamic model was used to describe the relationship between THC concentrations and changes in ICSS thresholds after cannabis smoke exposure.

Analysis of Direct Effects of the CB1 Receptor Antagonist Rimonabant on Fatty Acid Oxidation and Glycogenolysis in Liver and Muscle Cells in vitro.

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.

Activation of NPRs and UCP1-independent pathway following CB1R antagonist treatment is associated with adipose tissue beiging in fat-fed male dogs.

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.

A medium throughput rodent model of relapse from addiction with behavioral and pharmacological specificity

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 mGlu5 receptor antagonists MPEP and MTEP produced a significant reduction in reinstatement while failing to alter responding where every response produced food. The cannabinoid CB1 receptor antagonist rimonabant and the mGlu2/3 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.

Is Experimental Evolution of an Increased Aerobic Exercise Performance in Bank Voles Mediated by Endocannabinoid Signaling Pathway?

The level of physical activity achieved in a given situation depends on both physiological abilities and behavioral characteristics (motivation). We used a unique animal model to test a hypothesis that evolution of an increased aerobic exercise performance can be facilitated by evolution of motivation to undertake physical activity, mediated by brain endocannabinoid system. Bank voles (Myodes glareolus) from “aerobic” A lines selected for 22 generations for high swim-induced aerobic metabolism (VO2swim) achieved 65% higher “voluntary maximum” VO2swim than voles from unselected, “control” C lines. In C lines, VO2swim was 24% lower than the maximum forced-running aerobic metabolism (VO2run), while in A lines VO2swim and VO2run were practically the same. Thus, the selection changed both the aerobic capacity and motivation to exercise at the top performance level. We applied a pharmacological treatment manipulation to test a hypothesis that the endocannabinoid signaling pathway 1) affects the voles performance in the aerobic exercise trials, and 2) has been modified in the selection process. Administration of the CB1 receptor antagonist (Rimonabant) did not affect the level of metabolism, but administration of the endocannabinoid reuptake inhibitor (AM404) decreased VO2swim both in A and C lines (4%, p = 0.03) and tended to decrease VO2run (2%, p = 0.07). The significant effect of AM404 suggests the involvement of endocannabinoids in signaling pathways controlling the motivation to be active. However, the response to AM404 did not differ between A and C lines (interaction effect, p ≥ 0.29). Thus, the results did not provide a support to the hypothesis that modifications of endocannabinoid signaling have played a role in the evolution of increased aerobic exercise performance in our experimental evolution model system.Summary StatementThe results corroborated involvement of endocannabinoids in the regulation of physical activity, but did not support the hypothesis that modification of endocannabinoid signaling played a role in the evolution of increased aerobic exercise performance in our experimental evolution model.

Hedonic drinking engages a supraspinal inhibition of thermal nociception in adult rats.

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.

Cannabinoid CB1 Receptor Antagonist Rimonabant Decreases Levels of Markers of Organ Dysfunction and Alters Vascular Reactivity in Aortic Vessels in Late Sepsis in Rats.

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 CB1 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 12h 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 (10mg/kg, 4h 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.

Effects of fatty acid amide hydrolase inhibitor URB597 in a rat model of trauma-induced long-term anxiety

The endocannabinoid neurotransmitter, anandamide, has been implicated in the central modulation of stress responses. Previous animal experiments have shown that inhibitors of the anandamide-degrading enzyme, fatty acid amide hydrolase (FAAH), enhance the ability to cope with acute and chronic stress. Here, we investigated the effects of the globally active FAAH inhibitor URB597 in a rat model of predator stress-induced long-term anxiety. Rats exposed to 2,5-dihydro-2,4,5-trimethylthiazoline (TMT), a chemical constituent of fox feces, developed a persistent anxiety-like state, which was assessed 7days after exposure using the elevated plus maze (EPM) test. Systemic administration of URB597 [0.03-0.1-0.3mg/kg, intraperitoneal (ip)] 2h before testing suppressed TMT-induced behaviors with a median effective dose (IC50) of 0.075mg/kg. This effect was strongly correlated with inhibition of brain FAAH activity (r2 = 1.0) and was accompanied by increased brain levels of three FAAH substrates: the endocannabinoid anandamide and the endogenous peroxisome proliferator-activated receptor-α (PPAR-α) agonists, oleoylethanolamide (OEA), and palmitoylethanolamide (PEA). The anxiolytic-like effects of URB597 were blocked by co-administration of the CB1 receptor antagonist rimonabant (1mg/kg, ip), but not of the PPAR-α antagonist GW6471 (1mg/kg, ip). Finally, when administered 18h after TMT exposure (i.e., 6days before the EPM test), URB597 (0.3mg/kg, ip) prevented the consolidation of anxiety-like behavior in a CB1-dependent manner. The results support the hypothesis that anandamide-mediated signaling at CB1 receptors serves an important regulatory function in the stress response, and confirm that FAAH inhibition may offer a potential therapeutic strategy for post-traumatic stress disorder.

Developmental and behavioral effects in neonatal and adult mice following prenatal activation of endocannabinoid receptors by capsaicin.

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 CB1 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.

Examination of the effects of cannabinoid ligands on decision making in a rat gambling task

Although exposure to delta-9-tetrahydrocannabinol (THC) is perceived to be relatively harmless, mounting evidence has begun to show that it is associated with a variety of cognitive deficits, including poor decision making. THC-induced impairments in decision making are thought to be the result of cannabinoid CB1 receptor activation, and although clinical literature suggests that chronic activation via THC contributes to perturbations in decision making, acute CB1 receptor modulation has yielded mixed results. Using an animal model to examine how CB1-specific ligands impact choice biases would provide significant insight as to how recruitment of the endocannabinoid system may influence decision making. Here, we used the rat gambling task (rGT), a validated analogue of the human Iowa Gambling Task, to assess baseline decision making preferences in male Wistar rats. After acquisition rGT performance was measured. Animals were challenged with the CB1 receptor antagonist rimonabant, the partial agonist THC, and the synthetic agonist WIN55,212-2. Animals were also treated acutely with the fatty acid amide hydrolase (FAAH) inhibitor URB597 to selectively upregulate the endocannabinoid anandamide. Blockade of the CB1 receptor produced a trend improvement in decision making in animals who preferred the advantageous task options, yet left choice unaffected in risk-prone rats. Neither CB1 receptor agonist had strong effects on decision making, but a high dose THC decreased premature responses, whereas WIN55,212-2 did the opposite. URB597 did not affect task performance. These results indicate that although chronic CB1 receptor activation may be associated with impaired decision making, acute modulation has modest effects on choice and instead may play a substantive role in regulating impulsive responding.

Novel sulfenamides and sulfonamides based on pyridazinone and pyridazine scaffolds as CB1 receptor ligand antagonists

A series of sulfenamide and sulfonamide derivatives was synthesized and evaluated for the affinity at CB1 and CB2 receptors. The N-bornyl-S-(5,6-di-p-tolylpyridazin-3-yl)-sulfenamide, compound 11, displayed good affinity and high selectivity for CB1 receptors (Ki values of 44.6 nM for CB1 receptors and >40 μM for CB2 receptors, respectively). The N-isopinocampheyl-sulfenamide 12 and its sulfonamide analogue 22 showed similar selectivity for CB1 receptors with Ki values of 75.5 and 73.2 nM, respectively. These novel compounds behave as antagonists/inverse agonists at CB1 receptor in the [35S]-GTPγS binding assays, and none showed adequate predictive blood–brain barrier permeation, exhibiting low estimated LD50. However, testing compound 12 in a supraspinal analgesic test (hot-plate) revealed that it was as effective as the classic CB1 receptor antagonist rimonabant, in reversing the analgesic effect of a cannabinoid agonist.

Acetaminophen Relieves Inflammatory Pain through CB1 Cannabinoid Receptors in the Rostral Ventromedial Medulla.

Acetaminophen (paracetamol) is a widely used analgesic and antipyretic drug with only incompletely understood mechanisms of action. Previous work, using models of acute nociceptive pain, indicated that analgesia by acetaminophen involves an indirect activation of CB1 receptors by the acetaminophen metabolite and endocannabinoid reuptake inhibitor AM 404. However, the contribution of the cannabinoid system to antihyperalgesia against inflammatory pain, the main indication of acetaminophen, and the precise site of the relevant CB1 receptors have remained elusive. Here, we analyzed acetaminophen analgesia in mice of either sex with inflammatory pain and found that acetaminophen exerted a dose-dependent antihyperalgesic action, which was mimicked by intrathecally injected AM 404. Both compounds lost their antihyperalgesic activity in CB1-/- mice, confirming the involvement of the cannabinoid system. Consistent with a mechanism downstream of proinflammatory prostaglandin formation, acetaminophen also reversed hyperalgesia induced by intrathecal prostaglandin E2 To distinguish between a peripheral/spinal and a supraspinal action, we administered acetaminophen and AM 404 to hoxB8-CB1-/- mice, which lack CB1 receptors from the peripheral nervous system and the spinal cord. These mice exhibited unchanged antihyperalgesia indicating a supraspinal site of action. Accordingly, local injection of the CB1 receptor antagonist rimonabant into the rostral ventromedial medulla blocked acetaminophen-induced antihyperalgesia, while local rostral ventromedial medulla injection of AM 404 reduced hyperalgesia in wild-type mice but not in CB1-/- mice. Our results indicate that the cannabinoid system contributes not only to acetaminophen analgesia against acute pain but also against inflammatory pain, and suggest that the relevant CB1 receptors reside in the rostral ventromedial medulla.SIGNIFICANCE STATEMENT Acetaminophen is a widely used analgesic drug with multiple but only incompletely understood mechanisms of action, including a facilitation of endogenous cannabinoid signaling via one of its metabolites. Our present data indicate that enhanced cannabinoid signaling is also responsible for the analgesic effects of acetaminophen against inflammatory pain. Local injections of the acetaminophen metabolite AM 404 and of cannabinoid receptor antagonists as well as data from tissue-specific CB1 receptor-deficient mice suggest the rostral ventromedial medulla as an important site of the cannabinoid-mediated analgesia by acetaminophen.