CB1 Receptor Agonist Research Articles

Conditional deletion of CB2 cannabinoid receptors from peripheral sensory neurons eliminates CB2-mediated antinociceptive efficacy in a mouse model of carrageenan-induced inflammatory pain

CB2 cannabinoid receptor agonists suppress pathological pain in animal models and lack unwanted side effects commonly associated with direct activation of CB1 receptors. However, the types of pain most responsive to CB2 agonists are incompletely understood and cell types which underlie CB2-mediated therapeutic efficacy remain largely unknown. We previously reported that the CB2 receptor agonist LY2828360 reduced neuropathic nociception induced by toxic challenge with chemotherapeutic and anti-retroviral agents in mice. Whether these findings generalize to models of inflammatory pain is not known. Here we show that LY2828360 (10 mg/kg i.p.) reversed the maintenance of carrageenan-induced mechanical allodynia in female mice. Anti-allodynic efficacy was fully preserved in global CB1 knock out (KO) mice but absent in CB2 KO mice. The anti-allodynic efficacy of LY2828360 was absent in conditional KO (cKO) mice lacking CB2 receptors in peripheral sensory neurons (AdvillinCRE/+; CB2f/f) and preserved in cKO mice lacking CB2 receptors in microglia/macrophages expressing C-X3-C Motif Chemokine Receptor 1 (CX3CR1CRE/+; CB2f/f). Intraplantar administration of LY2828360 (30 μg i.pl.) reversed carrageenan-induced mechanical allodynia in CB2f/f but not AdvillinCRE/+; CB2f/f mice of both sexes. Thus, CB2 receptors in peripheral sensory neurons likely underlie the therapeutic effects of LY2828360 injection in the paw. Lastly, qRT-PCR analyses revealed that LY2828360 reduced carrageenan-induced increases in IL-1β and IL-10 mRNA in paw skin. Our results suggest that LY2828360 suppresses inflammatory nociception in mice through a neuronal CB2-dependent mechanism that requires peripheral sensory neuron CB2 receptors and suggest that the clinical applications of LY2828360 as an anti-hyperalgesic agent should be re-evaluated.

The electrophysiological and behavioral evaluation of the peptide hemopressin and cannabinoid CB1 receptor agonist and antagonist in pentylenetetrazol model of epilepsy in rats.

This study endeavoured to assess the effect of hemopressin (Hp), a nano peptide obtained from the alpha chain of hemoglobin, on chronic epileptic activity and its potential correlation with cannabinoid receptor type 1 (CB1). Male Wistar albino rats (230-260g) were used. The kindling process was conducted by administering a sub-convulsant dose of pentylenetetrazol (PTZ) (35mg/kg, i.p) three times a week for a maximum of 10weeks. Tripolar electrodes and external cannula guides for intracerebroventricular (i.c.v) injections were surgically implanted in the skulls of kindled rats. On the day of the experiment, doses of Hp, AM-251, and ACEA were administered prior to the PTZ injections. Electroencephalography recordings and behavioural observations were conducted simultaneously for 30min after the PTZ injection. The administration of Hp (0.6μg, i.c.v) resulted in a decrease in epileptic activity. The CB1 receptor agonist ACEA (7.5μg, i.c.v) showed an anticonvulsant effect, but the CB1 receptor antagonist AM-251 (0.5μg, i.c.v) displayed a proconvulsant effect. The co-administration of Hp (0.6μg, i.c.v) and ACEA (7.5μg, i.c.v) and of Hp (0.6μg, i.c.v) and AM-251 (0.5μg, i.c.v) produced an anticonvulsant effect. However, when AM-251 was administered prior to Hp, it produced a proconvulsant impact that overrode Hp's intended anticonvulsant effect. Interestingly, the co-administration of Hp (0.03μg) + AM-251 (0.125μg) unexpectedly exhibited an anticonvulsant effect. Electrophysiological and behavioural evaluations demonstrated the anticonvulsant effect of Hp in the present model, highlighting the possibility that Hp may act as an agonist for the CB1 receptor.

Structural basis of selective cannabinoid CB2 receptor activation

Cannabinoid CB2 receptor (CB2R) agonists are investigated as therapeutic agents in the clinic. However, their molecular mode-of-action is not fully understood. Here, we report the discovery of LEI-102, a CB2R agonist, used in conjunction with three other CBR ligands (APD371, HU308, and CP55,940) to investigate the selective CB2R activation by binding kinetics, site-directed mutagenesis, and cryo-EM studies. We identify key residues for CB2R activation. Highly lipophilic HU308 and the endocannabinoids, but not the more polar LEI-102, APD371, and CP55,940, reach the binding pocket through a membrane channel in TM1-TM7. Favorable physico-chemical properties of LEI-102 enable oral efficacy in a chemotherapy-induced nephropathy model. This study delineates the molecular mechanism of CB2R activation by selective agonists and highlights the role of lipophilicity in CB2R engagement. This may have implications for GPCR drug design and sheds light on their activation by endogenous ligands.

The Cannabinoid Ligand Arachidonyl-2'-Chloroethylamide (ACEA) Ameliorates Depressive and Overactive Bladder Symptoms in a Corticosterone-Induced Female Wistar Rat Model.

There is growing need to increase the knowledge on the cannabinoid ligands in the treatment of overactive bladder. Among potential candidates, arachidonyl-2'-chloroethylamide (ACEA), a selective cannabinoid CB1 receptor agonist is proposed. The aim of this paper was to determine if ACEA, a selective cannabinoid CB1 receptor agonist, could reverse the effects of corticosterone (CORT), characteristic of depressive and bladder overactivity potential. The animals (48 female rats) were divided into four groups: I-control, II-received CORT, III-received ACEA, and IV-received the combination of CORT and ACEA. The conscious cystometry, forced swim test (FST), and locomotor activity measurements were performed 3 days after the last dose of ACEA, followed by ELISA measurements. In group IV, ACEA restored urodynamic parameters that were altered by CORT. CORT prolonged the immobility time in FST and the values were lowered by ACEA. ACEA normalized the expression of c-Fos in all the analyzed central micturition centers (group IV vs. group II). ACEA restored the CORT-induced changes in the biomarkers in urine (BDNF, NGF), bladder detrusor (VAChT, Rho kinase), bladder urothelium (CGRP, ATP, CRF, OCT-3, TRPV1), and hippocampus (TNF-α, IL-1β and Il-6, CRF, IL-10, BDNF, NGF). In conclusion, ACEA was proven to reverse CORT-induced changes in both cystometric and biochemical parameters that are determinants of OAB/depression, which represents an example of an existing link between OAB and depression via cannabinoid receptors.

The Plant Derived 3-3'-Diindolylmethane (DIM) Behaves as CB2 Receptor Agonist in Prostate Cancer Cellular Models.

3-3'-Diindolylmethane (DIM) is a biologically active dimer derived from the endogenous conversion of indole-3-carbinol (I3C), a naturally occurring glucosinolate found in many cruciferous vegetables (i.e., Brassicaceae). DIM was the first pure androgen receptor antagonist isolated from the Brassicaceae family and has been recently investigated for its potential pharmacological use in prostate cancer prevention and treatment. Interestingly, there is evidence that DIM can also interact with cannabinoid receptors. In this context, by considering the well-known involvement of the endocannabinoid system in prostate cancer, we have pharmacologically characterized the properties of DIM on both CB1 and CB2 cannabinoid receptors in two human prostate cancer cell lines: PC3 (androgen-independent/androgen receptor negative) and LNCaP (androgen-dependent). In the PC3 cell line, DIM was able to activate CB2 receptors and potentially associated apoptotic pathways. On the other hand, although DIM was also able to activate CB2 receptors in the LNCaP cell line, no apoptotic effects were observed. Our evidence confirms that DIM is a CB2 receptor ligand and, moreover, it has a potential anti-proliferative effect on androgen-independent/androgen receptor-negative prostate cancer cells.

Behavioral, biochemical and histopathological toxic profiles induced by sub-chronic cannabimimetic WIN55, 212–2 administration in mice

WIN55, 212–2 mesylate is a synthetic cannabinoid (SC) agonist of CB1 and CB2 receptors with much higher affinity to CB1 receptor than tetrahydrocannabinol and many potential therapeutic effects. Few studies have evaluated SCs effects on more complex animal behavior and sex differences in cannabinoids toxicology. The current study was undertaken for determination of behavioral (Open Field test), biochemical (liver and kidney function test plus GABA & Glutamate levels), histopathological and CB1 immunohistochemistry risks of sub-chronic administration of SC WIN55, 212–2 mesylate in male and female mice. A total of 40 healthy adult mice were randomly divided into four groups (5 mice each): a negative control group, a vehicle group, a low dose (0.05 mg/kg) group and a high dose group (0.1 mg/kg) for each gender.Open Field Test revealed dose and gender-dependent anxiogenic effect with reduced locomotor activity in both sexes especially the higher doses with female mice being less compromised. GABA and glutamate levels increased significantly in both dose groups compared to controls alongside female mice versus males. No significant biochemical alterations were found in all groups with minimal histopathological changes. The CB1 receptors immunohistochemistry revealed a significant increase in the number of CB1 positive neurons in both low and high dose groups against controls with higher expression in female brains.ConclusionsThere were sexual dimorphism effects induced by sub-chronic exposure to WIN55, 212–2 with lesser female mice affection and dose-dependent influences.

Selective CB2 Receptor Agonist, HU-308, Reduces Systemic Inflammation in Endotoxin Model of Pneumonia-Induced Acute Lung Injury.

Acute respiratory distress syndrome (ARDS) and sepsis are risk factors contributing to mortality in patients with pneumonia. In ARDS, also termed acute lung injury (ALI), pulmonary immune responses lead to excessive pro-inflammatory cytokine release and aberrant alveolar neutrophil infiltration. Systemic spread of cytokines is associated with systemic complications including sepsis, multi-organ failure, and death. Thus, dampening pro-inflammatory cytokine release is a viable strategy to improve outcome. Activation of cannabinoid type II receptor (CB2) has been shown to reduce cytokine release in various in vivo and in vitro studies. Herein, we investigated the effect of HU-308, a specific CB2 agonist, on systemic and pulmonary inflammation in a model of pneumonia-induced ALI. C57Bl/6 mice received intranasal endotoxin or saline, followed by intravenous HU-308, dexamethasone, or vehicle. ALI was scored by histology and plasma levels of select inflammatory mediators were assessed by Luminex assay. Intravital microscopy (IVM) was performed to assess leukocyte adhesion and capillary perfusion in intestinal and pulmonary microcirculation. HU-308 and dexamethasone attenuated LPS-induced cytokine release and intestinal microcirculatory impairment. HU-308 modestly reduced ALI score, while dexamethasone abolished it. These results suggest administration of HU-308 can reduce systemic inflammation without suppressing pulmonary immune response in pneumonia-induced ALI and systemic inflammation.

Targeting mediodorsal thalamic CB1 receptors to inhibit dextromethorphan-induced anxiety/exploratory-related behaviors in rats: The post-weaning effect of exercise and enriched environment on adulthood anxiety

Dextromethorphan (DXM) is an effective over-the-counter antitussive with an alarming increase as an abused drug for recreational purposes. Although reports of the association between DXM administration and anxiety, there are few investigations into the underlying DMX mechanisms of anxiogenic action. Thus, the present study aimed to investigate the role of the mediodorsal thalamus (MD) cannabinoid CB1 receptors (CB1Rs) in DXM-induced anxiety/exploratory-related behaviors in adult male Wistar rats. Animals were bilaterally cannulated in the MD regions. After one week, anxiety and exploratory behaviors were measured using an elevated plus-maze task (EPM) and a hole-board apparatus. Results showed that DXM (3–7 mg/kg, i. p.) dose-dependently increased anxiety-like behaviors. Intra-MD administration of ACPA (2.5–10 ng/rat), a selective CB1 receptor agonist, decreased anxiety-like effects of DXM. The blockade of MD CB1 receptors by AM-251 (40–120 ng/rat) did not affect the EPM task. However, it potentiated the anxiogenic response of an ineffective dose of DXM (3 mg/kg) in the animals. Moreover, the effect of post-weaning treadmill exercise (TEX) and enriched environment (EE) were examined in adulthood anxiety under the drug treatments. Juvenile rats were divided into TEX/EE and control groups. The TEX/EE-juvenile rats were placed on a treadmill and then exposed to EE for five weeks. Interestingly, compared to untreated animals, post-weaning TEX/EE inhibited the anxiety induced by DXM or AM-251/DXM. It can be concluded that the MD endocannabinoid system plays an essential role in the anxiogenic effect of dextromethorphan. Moreover, post-weaning exercise alongside an enriched environment may have an inhibitory effect on adulthood anxiety-like behaviors.

The Endogenous Cannabinoid System and Nitric Oxide Interact in Modulation of Cold Stress-induced Analgesia

The aim of the present study was to estimate 1) whether the endogenous cannabinoid and the nitric oxide-ergic systems' interaction affects cold stress-induced analgesia (c-SIA), and 2) whether the possible interaction (and its impact on c-SIA) differs before and after cold-stress exposure.
 Male Wistar rats have been injected with CB1-receptor agonist anandamide (AEA) and the nitric oxide (NO) precursor L-arginine before and after 1 hour of cold stress (1 h CS) exposure; CB1 antagonist AM251, the nitric oxide synthase inhibitor L-NAME, and the NO-donor SIN-1 were additionally applied in order to further elucidate the interaction between the two systems.
 Results obtained suggest that endocannabinoids and NO differently interact before and after stress: applied before stress, the two systems were antagonistic between them with AEA exerting an analgesic effect, while NO decreased analgesia; a synergistic effect of endocannabinoids and NO resulted instead in application after 1 h CS.

Design, synthesis, and structure-activity relationships of diindolylmethane derivatives as cannabinoid CB2 receptor agonists.

3,3'-Diindolylmethane (DIM), a natural product-derived compound formed upon ingestion of cruciferous vegetables, was recently described to act as a partial agonist of the anti-inflammatory cannabinoid (CB) receptor subtype CB2 . In the present study, we synthesized and evaluated a series of DIM derivatives and determined their affinities for human CB receptor subtypes in radioligand binding studies. Potent compounds were additionally evaluated in functional cAMP accumulation and β-arrestin recruitment assays. Small substituents in the 4-position of both indole rings of DIM were beneficial for high CB2 receptor affinity and efficacy. Di-(4-cyano-1H-indol-3-yl)methane (46, PSB-19837, EC50 : cAMP, 0.0144 µM, 95% efficacy compared to the full standard agonist CP55,940; β-arrestin, 0.0149 µM, 67% efficacy) was the most potent CB2 receptor agonist of the present series. Di-(4-bromo-1H-indol-3-yl)methane (44, PSB-19571) showed higher potency in β-arrestin (EC50 0.0450 µM, 61% efficacy) than in cAMP accumulation assays (EC50 0.509 µM, 85% efficacy) while 3-((1H-indol-3-yl)methyl)-4-methyl-1H-indole (149, PSB-18691) displayed a 19-fold bias for the G protein pathway (EC50 : cAMP, 0.0652 µM; β-arrestin, 1.08 µM). DIM and its analogs act as allosteric CB2 receptor agonists. These potent CB2 receptor agonists have potential as novel drugs for the treatment of inflammatory diseases.

Ketamine Pharmacodynamics Entangled: Reply.

We thank Bowdle et al.1 for their interest in our article,2 and for the important issue they raise, paraphrased as follows: what is the best anthropocentric description of the “mind-altering” effects of a heterogeneous group of compounds and drugs that act at the brain and cause significant changes in mental state. The group of drugs that we are referring to includes N-methyl-d-aspartate (NMDA) receptor antagonists (ketamine, nitrous oxide, xenon), serotonergic psychedelics (5-HT2a receptor agonists psilocybin and lysergic acid diethylamide and serotonin-releasing 3,4-methylenedioxymethamphetamine), ayahuasca, cannabinoids (CB-1 receptor agonists), and κ-opioid receptor agonists Salvinorin A and B; this list is certainly not complete (see List of Psychedelic Drugs3). During the past two decades we studied ketamine, cannabis, and recently also psilocybin in patients and healthy volunteers and observed several similarities in the subjective expression of feelings and emotions during and after treatment. One important commonality is that these drug consumers display a certain disconnection or dissociation from reality. In this sense, the word “dissociation” and “dissociative drug” have a different meaning than described by Bowdle et al.1 It may indeed not be the correct wording because dissociation does not encompass all of the symptoms experienced and expressed by the users of these drugs (not all symptoms relate to a disconnect with reality). Moreover, there are clear distinctions in symptomatology between these different drugs. For example, the hallucinogenic effects of cannabinoids are very different from those of ketamine or ayahuasca. Hence, it may just not be possible to have one denominator that describes the mind-altering effects of these drugs. The conclusion of Bowdle et al.1 is that it is best to describe the anesthetic drugs that have psychedelic effects by their mechanism of action, for example, the NMDA-receptor antagonist ketamine. However, there is ample evidence that many of the ketamine effects are non-NMDA related. For example, acute pain relief may be related to the μ-opioid receptor and/or specific background potassium channels.4,5 Therefore, we argue that we need another approach. One term that describes both the NMDA-receptor antagonists and serotonergic psychedelics is psychoplastogen. Psychoplastogens are molecules that have a neurotrophic effect and promote rapid neural plasticity in the cortex (rewiring of pathologic neurocircuitry).6 Although this term does not describe the subjective experiences caused by these drugs, it does describe the mechanisms associated with their healing effects, whether it be antidepression or pain relief. Hence, in future studies we will refer to ketamine as a psychoplastogen. We thank Dr. Bowdle et al. for this mental exercise that we hope will result in an improved description of the behavioral effects of psychedelic drugs.The Anesthesia & Pain Research Unit of the Department of Anesthesiology, Leiden University Medical Center (Leiden, The Netherlands), received/receives funding from AMO Pharma Ltd. (Leeds, United Kingdom), Bedrocan BV (Veendam, the Netherlands), Grünenthal GmbH (Aachen, Germany), Medtronic (Minneapolis, Minnesota), MSD Nederland BV (Haarlem, the Netherlands), LTS Lohmann Therapie Systeme AG (Andernach, Germany), and Trevena Inc. (Chesterbrook, Pennsylvania). Dr. Dahan received consultancy and/or speaker fees from Enalare Therapeutics Inc. (Princeton, New Jersey), Grünenthal BV (Woerden, the Netherlands), Medasense Biometrics Ltd. (Ramat Gan, Israel). Dr. Dahan received grants/awards from ZonMW (The Hague, the Netherlands) and US Food and Drug Administration (Silver Spring, Maryland).

Structure-Activity Relationship Development Efforts towards Peripherally Selective Analogs of the Cannabinoid Receptor Partial Agonist BAY 59-3074.

Selective modulation of peripheral cannabinoid receptors (CBRs) has potential therapeutic applications in medical conditions, including obesity, diabetes, liver diseases, GI disorders and pain. While there have been considerable efforts to produce selective antagonists or full agonists of CBRs, there has been limited reports on the development of partial agonists. Partial agonists targeting peripheral CBRs may have desirable pharmacological profiles while not producing centrally mediated dissociative effects. Bayer reported that BAY 59-3074 is a CNS penetrant partial agonist of both CB1 and CB2 receptors with efficacy in rat models of neuropathic and inflammatory pain. In this report, we demonstrate our efforts to synthesize analogs that would favor peripheral selectivity, while maintaining partial agonism of CB1. Our efforts led to the identification of a novel compound, which is a partial agonist of the human CB1 (hCB1) receptor with vastly diminished brain exposure compared to BAY 59-3074.

Regulation of Expression of Cannabinoid CB2 and Serotonin 5HT1A Receptor Complexes by Cannabinoids in Animal Models of Hypoxia and in Oxygen/Glucose-Deprived Neurons.

Background: Cannabidiol (CBD) is a phytocannabinoid with potential in one of the most prevalent syndromes occurring at birth, the hypoxia of the neonate. CBD targets a variety of proteins, cannabinoid CB2 and serotonin 5HT1A receptors included. These two receptors may interact to form heteromers (CB2–5HT1A-Hets) that are also a target of CBD. Aims: We aimed to assess whether the expression and function of CB2–5HT1A-Hets is affected by CBD in animal models of hypoxia of the neonate and in glucose- and oxygen-deprived neurons. Methods: We developed a quantitation of signal transduction events in a heterologous system and in glucose/oxygen-deprived neurons. The expression of receptors was assessed by immuno-cyto and -histochemistry and, also, by using the only existing technique to visualize CB2–5HT1A-Hets fixed cultured cells and tissue sections (in situ proximity ligation PLA assay). Results: CBD and cannabigerol, which were used for comparative purposes, affected the structure of the heteromer, but in a qualitatively different way; CBD but not CBG increased the affinity of the CB2 and 5HT1A receptor–receptor interaction. Both cannabinoids regulated the effects of CB2 and 5HT1A receptor agonists. CBD was able to revert the upregulation of heteromers occurring when neurons were deprived of oxygen and glucose. CBD significantly reduced the increased expression of the CB2–5HT1A-Het in glucose/oxygen-deprived neurons. Importantly, in brain sections of a hypoxia/ischemia animal model, administration of CBD led to a significant reduction in the expression of CB2–5HT1A-Hets. Conclusions: Benefits of CBD in the hypoxia of the neonate are mediated by acting on CB2–5HT1A-Hets and by reducing the aberrant expression of the receptor–receptor complex in hypoxic-ischemic conditions. These results reinforce the potential of CBD for the therapy of the hypoxia of the neonate.

O-307 Cannabidiol as a potential novel treatment for endometriosis by its anti-inflammatory and anti-oxidative effects in an experimental rat model

Abstract Study question Can cannabidiol (CBD) - a nonpsychoactive constituent of the cannabis plant – be used in the treatment of endometriosis by its anti-inflammatory and anti-oxidative effects? Summary answer CBD appears to be a potential novel therapeutic agent in the treatment of endometriosis through inhibiting inflammation and decreasing oxidative stress in a dose-dependent manner. What is known already The endocannabinoid system (ECS) consists of various bioactive lipids that are produced endogenously which activate cannabinoid 1-2 receptors (CB1-2). Alterations in ECS are associated with many physiological and pathological conditions throughout the body including endometriosis. The events that play role in the development and growth of ectopic endometriotic implants are proliferation, angiogenesis, and inflammation. By their anti-inflammatory and anti-oxidative effects, phyto and synthetic cannabinoids had been investigated and started being used for diseases with similar mechanisms. CBD is a nonpsychoactive constituent of the cannabis plant which acts indirectly upon the CB-1 receptor and as an inverse agonist of CB-2 receptor. Study design, size, duration Endometrial implants were surgically induced in 36 female Wistar-Albino rats in the first surgery. After confirmation of endometriotic foci in the second surgery, the rats were randomized into four groups. Group 1 (leuprolide acetate group) was given a single 1 mg/kg subcutaneous injection of leuprolide acetate. Groups 2,3 and 4 were 5 mg/kg CBD, saline solution (control group), and 20 mg/kg CBD injected groups, respectively, and daily intra-peritoneal (i.p.) injections were applied for seven days. Participants/materials, setting, methods After 21 days from the second surgery, the rats were sacrificed and histopathological analysis of endometriotic lesions, total antioxidant status (TAS), total oxidant status (TOS), oxidative stress index (OSI), interleukin 1 (IL-1), interleukin 6 (IL-6) and tumor necrosis factor-alpha (TNF-a) measurements in blood and peritoneal fluid samples, and immunohistochemical staining for TNF-a expression in endometriotic tissue were evaluated. Main results and the role of chance After treatment, significant reductions in TOS, OSI, IL-1, IL-6 and TNF-α levels in the blood and peritoneal fluid samples and TNF-α expression of endometriotic implants (p < 0.01) and increased TAS (p < 0.01) were found in the CBD 5mg/kg and leuprolide acetate groups. Limitations, reasons for caution The limitation is that this is an experimental rat model study. Wider implications of the findings This is the first study in the literature that evaluates the effects of a phytocannabinoid -CBD- on endometriosis in a rat model. With its anti-inflammatory and anti-oxidative effects and favorable safety and tolerability profile, it might be a candidate for a novel treatment in endometriosis. Trial registration number not applicable

Phycocyanin stimulates ulcerative colitis healing via selective activation of cannabinoid receptor-2, intestinal mucosal healing, Treg accumulation, and p38MAPK/MK2 signaling inhibition

Ulcerative colitis (UC) is a chronic inflammatory condition that until this date, lacks curative treatments. Previously, synthetic selective CB2 receptor (CB2R) agonists demonstrated effective preclinical anti-inflammatory activities in UC. Phycocyanin (PC), photosynthetic assistant protein isolated from Microcystis aeruginosa Kützing blue green algae, has multiple pharmacological effects, however, it's effect against UC remains unexplored. Our study aimed at investigating the therapeutic effectiveness of PC against UC, and correlating its mechanisms with CB2R agonistic activities. In silico; PC showed structural similarity with endocannabinoid receptors' ligand “Δ9-tetrahydrocannabinol”, target prediction studies suggested high affinity for G-coupled protein family-receptors, and molecular docking affirmed preferable affinity towards CB2R vs CB1R. In LPS-exposed-Caco-2 cell line; PC demonstrated comparable interaction with CB2R, and downregulation of CB2R, p38 and MK2 gene expressions with reference agonist “6d”, and exhibited preferred selectivity towards CB2R over CB1R. In DSS-induced mice; PC-treatment ameliorated DSS-induced colon shortening, elevated disease activity index, and colonic pathological alterations. PC showed effective CB2R activation through potent anti-inflammatory activities, Treg-cell accumulation, suppression in p38MAPK/MK2 signaling, and tight junction barrier restoration as indicated by ultrastructural examinations, elevated ZO-1 and occludin protein expressions, and Ki67 immunohistochemical expression in colonic tissues. Additionally, PC alleviated intestinal dysbiosis via downregulating LPS/TLR4/NF-κB signaling and gut microbiota maintenance. Notably, PC-protective activities were abolished when co-administered with SR144528 (selective CB2 antagonist) except for gut microbiota maintenance, which was independent from CB2R activation. Our findings provide evidence of PC effectiveness against UC through acting as CB2R agonist, thus expanding its possible therapeutic application against other inflammatory diseases.

Basolateral amygdala cannabinoid CB1 receptors mediate the antinociceptive activity of harmaline in adolescent male mice

Evidence suggests a clear role for the amygdala endocannabinoid system in pain processing. Harmaline has been also known as the main nociceptive agent extracted from the Peganum harmala plant. In this study, the role of basolateral amygdala (BLA) cannabinoid CB1 receptors in pain sensitivity of harmaline-treated mice were assessed using tail-flick and hot plate methods in adolescent male NMRI mice. Intraperitoneal administration of two higher doses of harmaline (6 and 8 mg/kg) increased tail-flick latency, suggesting an antinociceptive activity. The same result was observed for the higher dose of harmaline in the hot plate test. Intra-BLA microinjection of CB1 receptor agonist ACPA (1 and 1.5 ng/mouse) or (1.5 ng/mouse) enhanced the ineffective dose-response of harmaline on pain threshold in the tail-flick or hot plate tests, respectively. Microinjection of two higher doses of CB1 receptor antagonist AM251 (0.5 and 1 ng/mouse) attenuated the antinociceptive activity of harmaline (8 ng/mouse) in both tail-flick and hot plate tests. Meanwhile, ACPA and AM251 did not alter latency to withdraw from the noxious stimulus in both tests, by themselves. It should be noted that the analgesic dose of the drugs alone or in combination did not affect locomotor activity. The obtained results highlight that BLA CB1 receptors mediate the antinociceptive activity of harmaline.

Motor-like Tics are Mediated by CB2 Cannabinoid Receptor-dependent and Independent Mechanisms Associated with Age and Sex

Δ9-Tetrahydrocannabinol (Δ9-THC) inhibits tics in individuals with Tourette syndrome (TS). Δ9-THC has similar affinities for CB1/CB2 cannabinoid receptors. However, the effect of HU-308, a selective CB2 receptor agonist, on repetitive behaviors has not been investigated. The effects of 2,5-dimethoxy-4-iodoamphetamine (DOI)-induced motor-like tics and Δ9-THC were studied with gene analysis. The effects of HU-308 on head twitch response (HTR), ear scratch response (ESR), and grooming behavior were compared between wildtype and CB2 receptor knockout (CB2−/−) mice, and in the presence/absence of DOI or SR141716A, a CB1 receptor antagonist/inverse agonist. The frequency of DOI-induced repetitive behaviors was higher in CB2−/− than in wildtype mice. HU-308 increased DOI-induced ESR and grooming behavior in adult CB2−/− mice. In juveniles, HU-308 inhibited HTR and ESR in the presence of DOI and SR141716A. HU-308 and beta-caryophyllene significantly increased HTR. In the left prefrontal cortex, DOI increased transcript expression of the CB2 receptor and GPR55, but reduced fatty acid amide hydrolase (FAAH) and α/β-hydrolase domain-containing 6 (ABHD6) expression levels. CB2 receptors are required to reduce 5-HT2A/2C-induced tics in adults. HU-308 has an off-target effect which increases 5-HT2A/2C-induced motor-like tics in adult female mice. The increased HTR in juveniles induced by selective CB2 receptor agonists suggests that stimulation of the CB2 receptor may generate motor tics in children. Sex differences suggest that the CB2 receptor may contribute to the prevalence of TS in boys. The 5-HT2A/2C-induced reduction in endocannabinoid catabolic enzyme expression level may explain the increased endocannabinoids’ levels in patients with TS.

Review of delta-8-tetrahydrocannabinol (Δ8 -THC): Comparative pharmacology with Δ9 -THC.

The use of the intoxicating cannabinoid delta-8-tetrahydrocannabinol (Δ8 -THC) has grown rapidly over the last several years. There have been dozens of Δ8 -THC studies dating back over many decades, yet no review articles have comprehensively covered these findings. In this review, we summarize the pharmacological studies of Δ8 -THC, including receptor binding, cell signalling, in vivo cannabimimetic activity, clinical activity and pharmacokinetics. We give special focus to studies that directly compared Δ8 -THC to its more commonly studied isomer, Δ9 -THC. Overall, the pharmacokinetics and pharmacodynamics of Δ8 -THC and Δ9 -THC are very similar. Δ8 -THC is a partial agonist of the cannabinoid CB1 receptor and has cannabimimetic activity in both animals and humans. The reduced potency of Δ8 -THC in clinical studies compared with Δ9 -THC can be explained by weaker cannabinoid CB1 receptor affinity, although there are other plausible mechanisms that may contribute. We highlight the gaps in our knowledge of Δ8 -THC pharmacology where further studies are needed, particularly in humans.

Cross state-dependent memory retrieval between cannabinoid CB1 and serotonergic 5-HT1A receptor agonists in the mouse dorsal hippocampus

Understanding the neurobiological mechanisms of drug-related learning and memory formation may help the treatment of cognitive disorders. Dysfunction of the cannabinoid and serotonergic systems has been demonstrated in learning and memory disorders.The present paper investigates the phenomenon called state-dependent memory (SDM) induced by ACPA (a selective cannabinoid CB1 receptor agonist) and 8-OH-DPAT (a nonselective 5-HT1A receptor agonist) with special focus on the role of the 5-HT1A receptor in the effects of both ACPA and 8-OH-DPAT SDM and cross state-dependent memory retrieval between ACPA and 8-OH-DPAT in a step-down inhibitory avoidance task.The dorsal hippocampal CA1 regions of adult male NMRI mice were bilaterally cannulated, and all drugs were microinjected into the intended injection sites. A single-trial step-down inhibitory avoidance task was used to assess memory retrieval and state-dependence.Post-training and/or pre-test microinjections of ACPA (1 and 2 ng/mouse) and 8-OH-DPAT (0.5 and 1 μg/mouse) dose-dependently induced amnesia. Pre-test administration of the same doses of ACPA and 8-OH-DPAT reversed the post-training ACPA- and 8-OH-DPAT-induced amnesia, respectively. This phenomenon has been named SDM. 8-OH-DPAT (1 μg/mouse) reversed the amnesia induced by ACPA (0.5, 1, and 2 ng/mouse) and induced ACPA SDM. ACPA (2 ng/mouse) reversed the amnesia induced by 8-OH-DPAT (0.25, 0.5, and 1 μg/mouse) and induced 8-OH-DPAT SDM. Pre-test administration of a 5-HT1A receptor antagonist, (S)-WAY 100,135 (0.25 and 0.5 μg/mouse), 5 min before ACPA and 8-OH-DPAT dose-dependently inhibited ACPA- and 8-OH-DPAT-induced SDM, respectively.The present study results demonstrated ACPA- and 8-OH-DPAT- induced SDM. Overall, the data revealed that dorsal hippocampal 5-HT1A receptor mechanisms play a pivotal role in modulating cross state-dependent memory retrieval between ACPA and 8-OH-DPAT.

Prolonged Activation of Brain CB2 Signaling Modulates Hypothalamic Microgliosis and Astrogliosis in High Fat Diet-Fed Mice.

Low-grade inflammation of the hypothalamus is associated with the disturbance of energy balance. The endocannabinoid system has been implicated in the development and maintenance of obesity as well as in the control of immune responses. The type 2 cannabinoid receptor (CB2) signaling has been associated with anti-inflammatory effects. Therefore, in high fat diet (HFD)-induced obese mice, we modulated CB2 signaling and investigated its effects on energy homeostasis and hypothalamic microgliosis/astrogliosis. We observed no effect on caloric intake and body weight gain in control diet-fed animals that received prolonged icv infusion of the CB2 receptor agonist HU308. Interestingly, we observed a decrease in glucose tolerance in HFD-fed animals treated with HU308. Prolonged icv infusion of HU308 increases astrogliosis in the ventromedial nucleus (VMH) of obese animals and reduced HFD-induced microgliosis in the hypothalamic arcuate (ARC) but not in the paraventricular (PVN) or VMH nuclei. These data indicate that central CB2 signaling modulates glucose homeostasis and glial reactivity in obesogenic conditions, irrespective of changes in body weight.