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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.

Skeletal muscle, constituting 40–50% of total body mass, is vital for mobility, posture, and systemic homeostasis. Muscle contraction heavily relies on ATP, primarily generated by mitochondrial oxidative phosphorylation. Mitochondria play a key role in decoding intracellular calcium signals. The endocannabinoid system (ECS), including CB1 receptors (CB1Rs), broadly influences physiological processes and, in muscles, regulates functions like energy metabolism, development, and repair. While plasma membrane CB1Rs (pCB1Rs) are well-established, a distinct mitochondrial CB1R (mtCB1R) population also exists in muscles, influencing mitochondrial oxidative activity and quality control. We investigated the role of mtCB1Rs in skeletal muscle physiology using a novel systemic mitochondrial CB1 deletion murine model. Our in vivo studies showed no changes in motor function, coordination, or grip strength in mtCB1 knockout mice. However, in vitro force measurements revealed significantly reduced specific force in both fast-twitch (EDL) and slow-twitch (SOL) muscles following mtCB1R ablation. Interestingly, knockout EDL muscles exhibited hypertrophy, suggesting a compensatory response to reduced force quality. Electron microscopy revealed significant mitochondrial morphological abnormalities, including enlargement and irregular shapes, correlating with these functional deficits. High-resolution respirometry further demonstrated impaired mitochondrial respiration, with reduced oxidative phosphorylation and electron transport system capacities in knockout mitochondria. Crucially, mitochondrial membrane potential dissipated faster in mtCB1 knockout muscle fibers, whilst mitochondrial calcium levels were higher at rest. These findings collectively establish that mtCB1Rs are critical for maintaining mitochondrial health and function, directly impacting muscle energy production and contractile performance. Our results provide new insights into ECS-mediated regulation of skeletal muscle function and open therapeutic opportunities for muscle disorders and aging.

The amygdala is composed of several nuclei, including the lateral nucleus which is the main receiving area for the input from cortical and subcortical brain regions. It mediates fear, anxiety, stress, and pain across species. Evidence suggests that the endocannabinoid system may be a promising target for modulating these processes. Cannabinoid and cannabinoid-related receptors have been identified in the amygdala of rodents, carnivores, and humans, but not in horses. This study aimed to investigate the gene expression of cannabinoid receptors 1 (CB1R) and 2 (CB2R), transient receptor potential vanilloid 1 (TRPV1), and peroxisome proliferator-activated receptor gamma (PPARγ) within the lateral nucleus of six equine amygdalae collected post mortem from an abattoir using quantitative real-time PCR, cellular distribution, and immunofluorescence. mRNA expression of CB1R and CB2R, but not TRPV1 or PPARγ, was detected. The percentage of immunoreactivity (IR) was calculated using ImageJ software. Cannabinoid receptor 1 immunoreactivity was absent in the somata but was strongly detected in the surrounding neuropil and varicosities and CB2R-IR was observed in the varicosities; TRPV1-IR showed moderate expression in the cytoplasm of somata and processes, while PPARγ-IR was weak-to-moderate in the neuronal nuclei. These findings demonstrate endocannabinoid system components in the equine amygdala and may support future studies on Cannabis spp. molecules acting on these receptors.

Cannabinoid receptors (CB1 and CB2), as part of the endocannabinoid system, play a critical role in numerous human physiological and pathological conditions. Thus, considerable efforts have been made to develop ligands for CB1 and CB2, resulting in hundreds of phyto- and synthetic cannabinoids which have shown varying affinities relevant for the treatment of various diseases. However, only a few of these ligands are clinically used. Recently, more detailed structural information for cannabinoid receptors was revealed thanks to the powerfulness of cryo-electron microscopy, which now can accelerate structure-based drug discovery. At the same time, novel peptide-type cannabinoids from animal sources have arrived at the scene, with their potential in vivo therapeutic effects in relation to cannabinoid receptors. From a natural products perspective, it is expected that more novel cannabinoids will be discovered and forecasted as promising drug leads from diverse natural sources and species, such as animal venoms which constitute a true pharmacopeia of toxins modulating diverse targets, including voltage- and ligand-gated ion channels, G protein-coupled receptors such as CB1 and CB2, with astonishing affinity and selectivity. Therefore, it is believed that discovering novel cannabinoids starting from studying the biodiversity of the species living on planet earth is an uncharted territory.

Arrestin translocation and signaling have come to the fore of the G protein-coupled receptor molecular pharmacology field. Some receptor-arrestin interactions are relatively well understood and considered responsible for specific therapeutic or adverse outcomes. Coupling of arrestins with cannabinoid receptors 1 (CB ) and 2 (CB ) has been reported, though the majority of studies have not systematically characterized the differential ligand dependence of this activity. In addition, many prior studies have utilized bovine (rather than human) arrestins, and the most widely applied assays require reporter-tagged receptors, which prevent meaningful comparison between receptor types. We have employed a bioluminescence resonance energy transfer (BRET) method that does not require the use of tagged receptors and thereby allows comparisons of arrestin translocation between receptor types, as well as with cells lacking the receptor of interest - an important control. The ability of a selection of CB and CB agonists to stimulate cell surface translocation of human and bovine β-arrestin-1 and -2 was assessed. We find that some CB ligands induce moderate β-arrestin-2 translocation in comparison with vasopressin V receptor (a robust arrestin recruiter); however, CB coupling with β-arrestin-1 and CB with either arrestin elicited low relative efficacies. A range of efficacies between ligands was evident for both receptors and arrestins. Endocannabinoid 2-arachidonoylglycerol stood out as a high efficacy ligand for translocation of β-arrestin-2 via CB . Δ -tetrahydrocannabinol was generally unable to elicit translocation of either arrestin subtype via CB or CB ; however, control experiments revealed translocation in cells not expressing CB /CB , which may assist in explaining some discrepancy with the literature. Overexpression of GRK2 had modest influence on CB /CB -induced arrestin translocation. Results with bovine and human arrestins were largely analogous, but a few instances of inconsistent rank order potencies/efficacies between bovine and human arrestins raise the possibility that subtle differences in receptor conformation stabilized by these ligands manifest in disparate affinities for the two arrestin species, with important potential consequences for interpretation in ligand bias studies. As well as contributing important information regarding CB /CB ligand-dependent arrestin coupling, our study raises a number of points for consideration in the design and interpretation of arrestin recruitment assays.

Objective Emerging evidence suggests lipid metabolism dysregulation contributes to autism spectrum disorders (ASD), with the endocannabinoid system (cannabinoid receptors CB1R/CB2R) implicated in lipid homeostasis. This study investigated whether CB1R/CB2R activation improves hippocampal lipid metabolism and ASD‐like behaviors in a valproic acid (VPA)‐induced ASD rat model. Methods Male offspring from dams exposed to VPA (600 mg/kg, i.p.) received the CB1R agonist ACPA (0.1 mg/kg) or the CB2R agonist AM1241 (3 mg/kg) from postnatal days 21–27. ASD‐like behaviors (marble burying, self‐grooming, social interaction, open‐field tests) and hippocampal lipid profiles (UPLC‐MS/MS) were analyzed. Results VPA‐exposed rats displayed heightened repetitive behaviors, social deficits, and hyperactivity, all significantly alleviated by ACPA and AM1241. Lipidomics revealed marked reductions in hippocampal phosphatidylcholines, lysophosphatidylcholines, fatty acids, sphingomyelins, ceramides, and phosphatidylethanolamines in VPA rats. Both agonists restored lipid levels to near normal, comparable to controls. Conclusions CB1R/CB2R activation ameliorates behavioral abnormalities and rectifies hippocampal lipid dysregulation in VPA‐induced ASD models, highlighting cannabinoid receptors as potential therapeutic targets for ASD‐associated metabolic disturbances. CB1R/CB2R activation ameliorates behavioral deficits and rectifies hippocampal lipid dysregulation in a VPA‐induced ASD rat model, highlighting the endocannabinoid system's therapeutic potential for autism spectrum disorders.

The endocannabinoid system has been found to be pervasive in mammalian species. It has also been described in invertebrate species as primitive as the Hydra. Insects, apparently, are devoid of this, otherwise, ubiquitous system that provides homeostatic balance to the nervous and immune systems, as well as many other organ systems. The endocannabinoid system (ECS) has been defined to consist of three parts, which include (1) endogenous ligands, (2) G-protein coupled receptors (GPCRs), and (3) enzymes to degrade and recycle the ligands. Two endogenous molecules have been identified as ligands in the ECS to date. The endocannabinoids are anandamide (arachidonoyl ethanolamide) and 2-AG (2-arachidonoyl glycerol). Two G-coupled protein receptors (GPCR) have been described as part of this system, with other putative GPC being considered. Coincidentally, the phytochemicals produced in large quantities by the Cannabis sativa L plant, and in lesser amounts by other plants, can interact with this system as ligands. These plant-based cannabinoids are termed phytocannabinoids. The precise determination of the distribution of cannabinoid receptors in animal species is an ongoing project, with the canine cannabinoid receptor distribution currently receiving the most interest in non-human animals.

RationaleWhile cannabis-based medicinal products have been shown to be effective for numerous neurological and psychiatric disorders, the evidence base regarding their adverse cognitive effects is poorly understood. The cannabinoid 1 receptor modulates memory performance via intracellular and extracellular mechanisms that alter synaptic transmission and plasticity. While previous literature has consistently shown that chronic cannabis users exhibit marked cognitive impairments, mixed findings have been reported in the context of placebo-controlled experimental trials. It is therefore unclear whether these compounds inherently alter cognitive processes or whether individuals who are genetically predisposed to use cannabis may have underlying cognitive deficits.ObjectiveWe conducted a meta-analysis to investigate the effects of full and partial cannabinoid 1 receptor (CB1R) agonists, antagonists, and negative allosteric modulators on non-spatial and spatial memory.MethodsIn accordance with the PRISMA guidelines, the EMBASE, MEDLINE, and PsycINFO databases were systematically searched for studies examining the effects of CB1R agonists, antagonists, and negative allosteric modulators on memory performance.ResultsWe systematically reviewed 195 studies investigating the effects of cannabinoid compounds on memory. In humans (N = 35 studies, comprising N = 782 subjects), delta-9-tetrahydrocannabinol (THC) (1.5–5 mg/kg) relative to placebo impaired performance on non-spatial memory tests, whereas only high THC doses (67 mg/kg) impaired spatial memory. Similarly, THC (0.2–4 mg/kg) significantly impaired visuospatial memory in monkeys and non-human primates (N = 8 studies, comprising N = 71 subjects). However, acute THC (0.002–10 mg/kg) had no effect on non-spatial (N = 6 studies, comprising 117 subjects; g = 1.72, 95% confidence interval (CI) − 0.18 to 3.63, p = 0.08) or spatial memory (9 studies, comprising 206 subjects; g = 0.75, 95% confidence interval (CI) − 1.09 to 2.58, p = 0.43). However, acute, full CB1R agonists significantly impaired non-spatial memory (N = 23 studies, 519 subjects; g = − 1.39, 95% CI − 2.72 to − 0.06, p = 0.03). By contrast, the chronic administration of CB1R agonists had no effect on non-spatial memory (N = 5 studies, comprising 146 subjects; g = − 0.05, 95% confidence interval (CI) − 1.32 to 1.22, p = 0.94). Moreover, the acute administration of CB1R antagonists had no effect on non-spatial memory in rodents (N = 9 studies, N = 149 subjects; g = 0.40, 95% CI − 0.11 to 0.92, p = 0.12).ConclusionsThe acute administration of THC, partial CB1R agonist, significantly impaired non-spatial memory in humans, monkeys, and non-human primates but not rodents. However, full CB1R agonists significantly impaired non-spatial memory in a dose-dependent manner but CB1R antagonists had no effect on non-spatial memory in rodents. Moreover, chronic THC administration did not significantly impair spatial or non-spatial memory in rodents, and there is inconclusive evidence on this in humans. Our findings highlight species differences in the effects of cannabinoid compounds on 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.