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The Cannabis sativa plant contains more than 120 cannabinoids. With the exceptions of ∆ 9 -tetrahydrocannabinol (∆ 9 -THC) and cannabidiol (CBD), comparatively little is known about the pharmacology of the less-abundant plant-derived (phyto) cannabinoids. The best-studied transducers of cannabinoid-dependent effects are type 1 and type 2 cannabinoid receptors (CB1R, CB2R). Partial agonism of CB1R by ∆ 9 -THC is known to bring about the ‘high’ associated with Cannabis use, as well as the pain-, appetite-, and anxiety-modulating effects that are potentially therapeutic . CB2R activation by certain cannabinoids has been associated with anti-inflammatory activities. We assessed the activity of 8 phytocannabinoids at human CB1R, and CB2R in Chinese hamster ovary (CHO) cells stably expressing these receptors and in C57BL/6 mice in an attempt to better understand their pharmacodynamics. Specifically, ∆ 9 -THC, ∆ 9 -tetrahydrocannabinolic acid (∆ 9 -THCa), ∆ 9 -tetrahydrocannabivarin (THCV), CBD, cannabidiolic acid (CBDa), cannabidivarin (CBDV), cannabigerol (CBG), and cannabichromene (CBC) were evaluated. Compounds were assessed for their affinity to receptors, ability to inhibit cAMP accumulation, βarrestin2 recruitment, receptor selectivity, and ligand bias in cell culture; and cataleptic, hypothermic, anti-nociceptive, hypolocomotive, and anxiolytic effects in mice. Our data reveal partial agonist activity for many phytocannabinoids tested at CB1R and/or CB2R, as well as in vivo responses often associated with activation of CB1R. These data build on the growing body of literature showing cannabinoid receptor-dependent pharmacology for these less-abundant phytocannabinoids and are critical in understanding the complex and interactive pharmacology of Cannabis -derived molecules.

The cannabinoid receptor 1 (CB ) is the principal target of the psychoactive constituent of marijuana, the partial agonist Δ -tetrahydrocannabinol (Δ -THC). Here we report two agonist-bound crystal structures of human CB in complex with a tetrahydrocannabinol (AM11542) and a hexahydrocannabinol (AM841) at 2.80 Å and 2.95 Å resolution, respectively. The two CB -agonist complexes reveal important conformational changes in the overall structure, relative to the antagonist-bound state, including a 53% reduction in the volume of the ligand-binding pocket and an increase in the surface area of the G-protein-binding region. In addition, a 'twin toggle switch' of Phe200 and Trp356 (superscripts denote Ballesteros-Weinstein numbering) is experimentally observed and appears to be essential for receptor activation. The structures reveal important insights into the activation mechanism of CB and provide a molecular basis for predicting the binding modes of Δ -THC, and endogenous and synthetic cannabinoids. The plasticity of the binding pocket of CB seems to be a common feature among certain class A G-protein-coupled receptors. These findings should inspire the design of chemically diverse ligands with distinct pharmacological properties.

Combining patch-clamp recordings and subsequent STORM imaging of individual cells, the authors show that the axon terminals of perisomatically- and dendritically-projecting GABAergic interneurons show differences in CB 1 receptor number, active zone complexity, and receptor:effector ratio. Chronic exposure to THC evoked a dose-dependent and long-lasting downregulation of CB 1 at these synapses. A major challenge in neuroscience is to determine the nanoscale position and quantity of signaling molecules in a cell type– and subcellular compartment–specific manner. We developed a new approach to this problem by combining cell-specific physiological and anatomical characterization with super-resolution imaging and studied the molecular and structural parameters shaping the physiological properties of synaptic endocannabinoid signaling in the mouse hippocampus. We found that axon terminals of perisomatically projecting GABAergic interneurons possessed increased CB 1 receptor number, active-zone complexity and receptor/effector ratio compared with dendritically projecting interneurons, consistent with higher efficiency of cannabinoid signaling at somatic versus dendritic synapses. Furthermore, chronic Δ 9 -tetrahydrocannabinol administration, which reduces cannabinoid efficacy on GABA release, evoked marked CB 1 downregulation in a dose-dependent manner. Full receptor recovery required several weeks after the cessation of Δ 9 -tetrahydrocannabinol treatment. These findings indicate that cell type–specific nanoscale analysis of endogenous protein distribution is possible in brain circuits and identify previously unknown molecular properties controlling endocannabinoid signaling and cannabis-induced cognitive dysfunction.

Cannabinoids affect CB 1 receptors on the mitochondrial membranes in the brain, triggering a decrease in downstream cAMP-dependent signalling; this leads to a decrease in brain mitochondrial activity and to cannabinoid-induced amnesia. Bioenergetics deficiency and memory The pathological effect of chronic mitochondrial dysfunction on cognitive function is well established, however the acute modulation of neural processing by mitochondrial signalling is less well understood. These authors demonstrate that acute functional disruption of the brain by cannabinoids involves the activation and signalling from mitochondrial cannabinoid receptors. Thus, even acute mitochondrial bioenergetic changes or disruption can have a short-term effect on cognition, underscoring the role that mitochondria have in regulating normal brain activity. Cellular activity in the brain depends on the high energetic support provided by mitochondria, the cell organelles which use energy sources to generate ATP 1 , 2 , 3 , 4 . Acute cannabinoid intoxication induces amnesia in humans and animals 5 , 6 , and the activation of type-1 cannabinoid receptors present at brain mitochondria membranes (mtCB 1 ) can directly alter mitochondrial energetic activity 7 , 8 , 9 . Although the pathological impact of chronic mitochondrial dysfunctions in the brain is well established 1 , 2 , the involvement of acute modulation of mitochondrial activity in high brain functions, including learning and memory, is unknown. Here, we show that acute cannabinoid-induced memory impairment in mice requires activation of hippocampal mtCB 1 receptors. Genetic exclusion of CB 1 receptors from hippocampal mitochondria prevents cannabinoid-induced reduction of mitochondrial mobility, synaptic transmission and memory formation. mtCB 1 receptors signal through intra-mitochondrial Gα i protein activation and consequent inhibition of soluble-adenylyl cyclase (sAC). The resulting inhibition of protein kinase A (PKA)-dependent phosphorylation of specific subunits of the mitochondrial electron transport system eventually leads to decreased cellular respiration. Hippocampal inhibition of sAC activity or manipulation of intra-mitochondrial PKA signalling or phosphorylation of the Complex I subunit NDUFS2 inhibit bioenergetic and amnesic effects of cannabinoids. Thus, the G protein-coupled mtCB 1 receptors regulate memory processes via modulation of mitochondrial energy metabolism. By directly linking mitochondrial activity to memory formation, these data reveal that bioenergetic processes are primary acute regulators of cognitive functions.

The CB1 receptor mediates the central nervous system response to cannabinoids, and is a drug target for pain, anxiety and seizures. CB1 also responds to allosteric modulators, which influence cannabinoid binding and efficacy. To understand the mechanism of these compounds, we solved the crystal structure of CB1 with the negative allosteric modulator (NAM) ORG27569 and the agonist CP55940. The structure reveals that the NAM binds to an extrahelical site within the inner leaflet of the membrane, which overlaps with a conserved site of cholesterol interaction in many G protein-coupled receptors (GPCRs). The ternary structure with ORG27569 and CP55940 captures an intermediate state of the receptor, in which aromatic residues at the base of the agonist-binding pocket adopt an inactive conformation despite the large contraction of the orthosteric pocket. The structure illustrates a potential strategy for drug modulation of CB1 and other class A GPCRs. A crystal structure of the GPCR target of endocannabinoid signaling lipids and drugs, CB1, bound to a negative allosteric modulator (NAM) and an agonist, shows that the NAM binds to a membrane-embedded site reminiscent of the binding site of cholesterol.

The endocannabinoid system via cannabinoid (CB: CB1 and CB2) receptors and their endogenous ligands is directly and indirectly involved in many physiological functions, especially in memory and learning processes. Extensive studies reported that this system strictly modulates cognition-related processes evaluated in various animal models. However, the effects of cannabinoids on the cognition have been contradictory. The cannabinoid compounds were able to both impair or improve different phases of memory processes through direct (receptor related) or indirect (non-receptor related) mechanism. The memory-related effects induced by the cannabinoids can be depended on the kind of cannabinoid compound used, dosage, and route of administration as well as on the memory task chosen. Therefore, the objectives of this paper are to review and summarize the results describing the role of endocannabinoid system in cognition, including various stages of memory.

The endocannabinoid (eCB) system is widely expressed in many central and peripheral tissues, and is involved in a plethora of physiological processes. Among these, activity of the eCB system promotes energy intake and storage, which, however, under pathophysiological conditions, can favour the development of obesity and obesity-related disorders. It is proposed that eCB signalling is evolutionary beneficial for survival under periods of scarce food resources. Remarkably, eCB signalling is increased both in hunger and in overnutrition conditions, such as obesity and type-2 diabetes. This apparent paradox suggests a role of the eCB system both at initiation and at clinical endpoint of obesity. This review will focus on recent findings about the role of the eCB system controlling whole-body metabolism in mice that are genetically modified selectively in different cell types. The current data in fact support the notion that eCB signalling is not only engaged in the development but also in the maintenance of obesity, whereby specific cell types in central and peripheral tissues are key sites in regulating the entire body’s energy homeostasis.

Endocannabinoids such as anandamide [N-arachidonoylethanolamine (AEA)] and 2-arachidonoyl glycerol (2-AG) are known orexigenic mediators that act via CB₁ receptors in hypothalamus and limbic forebrain to induce appetite and stimulate food intake. Circulating endocannabinoid levels inversely correlate with plasma levels of leptin, an anorexigenic mediator that reduces food intake by acting on hypothalamic receptors. Recently, taste has been found to be a peripheral target of leptin. Leptin selectively suppresses sweet taste responses in wild-type mice but not in leptin receptor-deficient db/db mice. Here, we show that endocannabinoids oppose the action of leptin to act as enhancers of sweet taste. We found that administration of AEA or 2-AG increases gustatory nerve responses to sweeteners in a concentration-dependent manner without affecting responses to salty, sour, bitter, and umami compounds. The cannabinoids increase behavioral responses to sweet-bitter mixtures and electrophysiological responses of taste receptor cells to sweet compounds. Mice genetically lacking CB₁ receptors show no enhancement by endocannnabinoids of sweet taste responses at cellular, nerve, or behavioral levels. In addition, the effects of endocannabinoids on sweet taste responses of taste cells are diminished by AM251, a CB₁ receptor antagonist, but not by AM630, a CB₂ receptor antagonist. Immunohistochemistry shows that CB₁ receptors are expressed in type II taste cells that also express the T1r3 sweet taste receptor component. Taken together, these observations suggest that the taste organ is a peripheral target of endocannabinoids. Reciprocal regulation of peripheral sweet taste reception by endocannabinoids and leptin may contribute to their opposing actions on food intake and play an important role in regulating energy homeostasis.

There are two well-characterized cannabinoid receptors (CB1R and CB2R and other candidates): the central nervous system (CNS) enriched CB1R and peripheral tissue enriched CB2R with a wide dynamic range of expression levels in different cell types of human tissues. Hepatocytes and neurons express low baseline CB1R and CB2R, respectively, and their cell-type-specific functions are not well defined. Here we report inducible expression of CB1R in the liver by high-fat and high sugar diet and CB2R in cortical neurons by methamphetamine. While there is less controversy about hepatocyte CB1R, the presence of functional neuronal CB2R is still debated to date. We found that neuron CB2R basal expression was higher than that of hepatocyte CB1R by measuring mRNA levels of specific isoform CB2A in neurons isolated by fluorescence-activated cell sorting (FACS) and CB1A in hepatocytes isolated by collagenase perfusion of liver. For in vivo studies, we generated hepatocyte, dopaminergic neuron, and microglia-specific conditional knockout mice (Abl-Cnr1Δ, Dat-Cnr2Δ, and Cx3cr1-Cnr2Δ) of CB1R and CB2R by crossing Cnr1f/f and Cnr2f/f strains to Abl-Cre, Dat-Cre, and Cx3cr1-Cre deleter mouse strains, respectively. Our data reveals that neuron and microglia CB2Rs are involved in the “tetrad” effects of the mixed agonist WIN 55212-2, CB1R selective agonist arachidonyl-2′-chloroethylamide (ACEA), and CB2R selective agonist JWH133. Dat-Cnr2Δ and Cx3cr1-Cnr2Δ mice showed genotypic differences in hypomobility, hypothermia, analgesia, and catalepsy induced by the synthetic cannabinoids. Alcohol conditioned place preference was abolished in DAT-Cnr2Δ mice and remained intact in Cx3cr1-Cnr2Δ mice in comparison to WT mice. These Cre-loxP recombinant mouse lines provide unique approaches in cannabinoid research for dissecting the complex endocannabinoid system that is implicated in many chronic disorders.

With rapid expansion of cannabis legalization worldwide, rates of cannabis use and cannabis use disorder (CUD) are increasing; the need for safe and effective medications to treat CUD is urgent. This narrative review evaluates evidence for promising pharmacotherapies to treat CUD from randomized, placebo-controlled trials. Pharmacotherapies for CUD are categorized based on compound targets (e.g . , cannabinoid receptor 1 [CB1] agonists such as nabilone, serotonergic compounds such as bupropion, GABAergic compounds such as zolpidem) and outcomes are organized by predetermined withdrawal symptoms, cannabis craving, and cannabis relapse/use. Most promising pharmacotherapies for CUD are drugs that act on the endocannabinoid system and specifically at the CB1 receptor. Priority populations such as females, certain racial/ethnic groups, and age groups experience a different course of CUD progression, symptoms, and drug effects that are important to consider when evaluating outcomes related to CUD. Possible explanations for these disparities are explored, along with the clinical trials that explore these demographics in treating CUD with pharmacotherapies.