Objective:Cannabidiol (CBD) administration (5 mg/kg) in healthy rats has been shown to significantly decrease lymphocyte subset numbers in peripheral blood without involvement of natural killer cells. The aim was to evaluate whether lymphocyte numbers also decrease in the spleen.Introduction:CBD, the major non-psychotropic compound of Cannabis sp., is an effective treatment for inflammatory and autoimmune diseases with various anti-tumor effects, but the mechanisms of its long-term actions in vivo remain unclear.Methods:To examine the effects of CBD on lymphocyte subsets in the spleen and NK cellular cytotoxicity (NKCC), adult male Wistar rats (n = 63) were administered intraperitoneal injections of CBD (2.5 or 5 mg/kg/day) for 14 consecutive days, and lymphocyte counts were obtained using flow cytometry. NKCC in the peripheral blood and spleen was quantified using a Chromium-51 release assay. Furthermore, the effect was similar to a decrease in lymphocytes caused by treatment with the selective receptor antagonist AM630 (1 mg/kg).Results:The results indicate that repeated administration of CBD at a dose of 5 mg/kg/day decreased splenic lymphocyte numbers, involving T and non-T/NK CD45RA+ lymphocytes but not NK cells. The effects of CB2 receptor antagonist were not significant, but it had a significant interaction with CBD. No changes in NKCC were observed following CBD administration.Conclusion:These results reveal that in healthy rats, CBD produces similar lymphopenic effects in the spleen as it does in peripheral blood without affecting NK cell counts or cytotoxicity.

The endocannabinoid (eCB) system has risen as a critical modulator linking the environmental challenges to behavioral maladaptation, such as trait anxiety and reward learning impairment. However, the association between trait anxiety and reward learning and how they share molecular mechanism in eCB system is still unknown. Here, we utilized a series of behavioral tests to screen the correlation among the behavioral patterns, especially between trait anxiety and reward learning. The elevated platform stress and open field test (OFT) were employed to classify the mice into the different level of trait anxiety, and ethanol-induced conditioned place preference (CPP) was used to assess the ability of reward learning. Our results indicated that high trait anxiety (HTA) mice exhibited increased reward learning. Intracranial administration of the cannabinoid CB1 receptor (CB1R) antagonist AM-251 or agonist WIN55,212-2 in nucleus accumbens (NAc) showed the different effect on anxiety-like behavior and reward learning. Similarly, CB1R knockout in VTA dopaminergic (VTADA) neurons resulted in anxiety-like behavior and reward learning impairment. Thus, we reveal insight into the role of CB1R in dopaminergic circuit from VTA to NAc, and present the evidence for a shared molecular mechanism between anxiety and reward learning.

Adolescent CB1 receptor expression at the BLA and CA1 and acute AM251 effects on sociability and emotional memory are sex-specific, and not modulated by heterotypic stress exposure.

Cognitive decline is a hallmark of Alzheimer's disease (AD). Cannabidiol (CBD), a non-intoxicating phytocannabinoid with immunomodulatory properties, shows promise in alleviating AD symptoms. This study examined the effects of chronic CBD treatment in a male rat model of sporadic AD induced by intracerebroventricular streptozotocin (ICV-STZ) and explored its impact on neuroinflammatory genes and cannabinoid signaling. STZ rats showed impaired performance in object location and recognition tasks, along with reduced social behavior. STZ exposure also affected AD-related hippocampal markers, leading to increased levels of amyloid β-protein (Aβ) and tau phosphorylation (p-Tau) and elevated mRNA levels of triggering receptor expressed on myeloid cells 2 (TREM2) and apolipoprotein E4 (APOEε4). Additionally, STZ increased hippocampal neuroinflammatory markers, including mRNA levels of Tumor Necrosis Factor α (TNF-α), nuclear factor kappa B subunit 1 (NF-κB1), and interleukin (IL)-1β. It also altered cannabinoid receptor expression, with cannabinoid receptor 1 (cnr1) and 2 (cnr2) genes upregulated in the dentate gyrus (DG), whereas in the CA1, cnr2 was upregulated and cnr1 downregulated. Chronic CBD treatment restored the STZ-induced behavioral deficits, reduced neuroinflammatory marker expression, and mitigated AD-associated changes. Importantly, the CB1 receptor antagonist AM251, but not CB2 antagonist AM630, blocked the beneficial effects of CBD on performance in object location and social tasks in STZ-treated rats, highlighting CB1 receptor activation as a key mechanism. These findings suggest that CBD holds promise as a therapeutic agent for inflammation-induced AD, with the potential to ameliorate cognitive deficits and prevent disease onset through mechanisms involving CB1 receptor activation and modulation of neuroinflammation.

Role of endocannabinoid neurotransmission in the insular cortex on cardiovascular, autonomic and behavioral responses evoked by acute restraint stress in rats.

The cannabinoid CB2 receptor mediates the analgesic effects of Cannabis sativa extract in a rat model of neuropathic pain.

The endocannabinoid system (ECS) is one of the most important systems modulating functions in the body. The ECS, via cannabinoid (CB: CB1 and CB2) receptors, endocannabinoids occurring in the brain (e.g., anandamide (AEA) and 2-arachidonoylglycerol (2-AG)) and enzymes degrading endocannabinoids in the brain (fatty-acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL)), plays a key role in the regulation of mood and anxiety. However, the effects of cannabinoid compounds on anxiety-related responses are complex and yield mixed results depending on the type of pharmacological manipulation (direct or indirect) of functions of the ECS, as well as the kinds of cannabinoids, dosage and procedure. The aim of this study was to determine and compare the influence of the direct (via CB receptors ligands) and indirect (via inhibition of enzymes degrading endocannabinoids in the brain) pharmacological modulation of ECS function on anxiety-like responses in mice in the elevated plus maze (EPM) test. For this purpose, in the first step of the experiments, we used selected ligands of CB1, CB1/CB2 and CB2 receptors to assess which types of CB receptors are involved in anxiety-related responses in mice. Next, we used inhibitors of FAAH (which breaks down AEA) or MAGL (which breaks down 2-AG) to assess which endocannabinoid is more responsible for anxiety-related behavior in mice. The results of our presented research showed that an acute administration of CB1 receptor agonist oleamide (5-20 mg/kg) had no influence on anxiety-related responses and CB1 receptor antagonist AM 251 (0.25-3 mg/kg) had anxiogenic effects in the EPM test in mice. In turn, an acute administration of mixed CB1/CB2 receptor agonist WIN55,212-2 used at a dose of 1 mg/kg had an anxiolytic effect observed in mice in the EPM test. What is of interest is that both the acute administration of a CB2 receptor agonist (JWH 133 at the doses of 1 and 2 mg/kg) and antagonist (AM 630 at the doses of 0.5-2 mg/kg) had anxiogenic effects in this procedure. Moreover, we revealed that an acute administration of only FAAH inhibitor URB 597 (0.3 mg/kg) had an anxiolytic effect, while MAGL inhibitor JZL 184 (at any used doses (2-40 mg/kg)) after an acute injection had no influence on anxiety behavior in mice, as observed in the EPM test. In our experiments, we confirmed the clearly significant involvement of the ECS in anxiety-related responses. In particular, the pharmacological indirect manipulation of ECS functions is able to elicit promising anxiolytic effects. Therefore, the ECS could be a potential target for novel anxiolytic drugs; however, further studies are needed.

The endocannabinoid modulation of fear and anxiety due to their on-demand synthesis and degradation is supported by a large body of research. Although it has been proposed that the anandamide (AEA) in the globus pallidus (GP) seems to be important for the modulation of innate fear-related behaviours, a role for endogenous AEA has yet to be clarified. Rats were treated with the fatty acid amide hydrolase (FAAH) selective inhibitor URB597 at different concentrations (0.01, 0.1, 1 nmol/ 0.1 µL) in the GP followed by bicuculline microinjections in dlSC and confronted by a lancehead pit viper (Bothrops jararaca) in the enriched polygonal arena for snake panic test. The most effective dose of URB597 (1 nmol) was also preceded by microinjections of the CB1 receptor antagonist AM251 (0.1 nmol) in the GP, and rats were then confronted by venomous snakes. URB597 (0.1 and 1 nmol) in the GP decreased the expression of defensive behaviours such as defensive attention, escape, and time spent inside the burrow of animals confronted by pit vipers. Moreover, the pretreatment of the GP with AM251 suppressed these antiaversive effects of URB597 in such midbrain structure. Overall, these data clearly indicate that the panicolytic consequences of the endogenous AEA enhancement in the GP are mediated by CB1 receptors signalling.

INTERACTION BETWEEN THE DOPAMINERGIC AND ENDOCANNABINOID SYSTEMS PROMOTES PERIPHERAL ANTINOCICEPTION.

While low-dose cannabinoid 2 (CB2) receptor agonists attenuate morphine tolerance in cancer pain models, chemokine ligand 12 (CXCL12)/chemokine receptor 4 (CXCR4) expression induces morphine tolerance. Whether CB2 receptor agonists attenuate morphine tolerance by modulating CXCL12/CXCR4 signaling or whether CXCL12/CXCR4 signaling affects the mu opioid receptor (MOR) in the development of morphine tolerance in cancer pain remains unclear. In this study, we investigated the attenuation of morphine tolerance by a non-analgesic dose of the CB2 receptor agonist AM1241, focusing specifically on the modulation of CXCL12/CXCR4 signaling and its effect on the MOR. Rats received intrathecal Walker 256 tumor cell implantations and were treated with morphine combined with the intrathecal injection of AM1241 or the CB2 receptor antagonists AM630 and AM1241, or a CXCL12-neutralizing antibody, exogenous CXCL12, or the CXCR4 antagonist AMD3100. Our results show that CXCL12 and CXCR4 levels increased significantly in morphine-tolerant rats and were reduced by AM1241 pretreatment, which was reversed by AM630. CXCL12/CXCR4 expression accelerated the development of morphine tolerance and downregulated MOR expression. CXCR4 colocalized with MOR and CB2. Therefore, a non-analgesic dose of AM1241 attenuated morphine tolerance via CXCL12/CXCR4 signaling, whereas CXCL12/CXCR4 signaling participated in the development of morphine tolerance, potentially by modulating MOR expression in Walker 256 tumor-bearing rats.Graphical

Alzheimer's disease is a neurodegenerative disease that is characterized by the accumulation of two different proteins, β-amyloid and tau. The objective of the present study was to examine the impact of bilateral administration of the cannabinoid receptor antagonist (AM251) in the hippocampus on spatial memory and tau gene expression in an Alzheimer's disease model. The β-amyloid toxin was administered bilaterally into the hippocampus of Wistar male rats to induce Alzheimer's disease. The rats were then divided into four groups: the control group (which received distilled water as a solvent for β-amyloid toxin), the lesion group (which received the β-amyloid), β-amyloid + DMSO group (as antagonist solvent), and the AM251 antagonist receiving groups. During the training course of the Morris water maze test, the antagonist of the cannabinoid 1 receptor antagonist AM251 was administered bilaterally into the hippocampus for four consecutive days at doses of 5, 25, and 100 ng. To evaluate the spatial memory of the animals, the following parameters were analyzed: distance traveled, latency time to reach the hidden platform, velocity of the animals, and tau gene expression in real time. The spatial memory indices were found to be impaired following the injection of β-amyloid and the AM251 cannabinoid antagonist. Following the injection of β-amyloid toxin, there was an increase in mRNA expression of tau protein. However, no significant difference was observed between the cannabinoid antagonist and β-amyloid groups. These results indicate that β-amyloid toxin has a destructive effect on spatial memory and that cannabinoid system plays a positive role in memory formation and consolidation, However, further studies are needed to confirm these findings.

Visual exposure to dim, green, light has been found to reduce pain levels in patients living with migraine, low back pain, and fibromyalgia. Preclinical studies discovered that the analgesic effect of green light was due to the central release of endogenous opioids and a reduction in inflammatory cytokines in the cerebrospinal fluid. The present study assessed the effect of green light therapy (GLT) on joint pain in a rat model of osteoarthritis (OA) and investigated the role of endolipids. Male and female Wistar rats (207-318 g) received an intra-articular injection of sodium monoiodoacetate (3 mg in 50 μL saline) into the knee to induce OA. On day 9, animals were placed in a room illuminated by either white (neutral-white 4000K; 20 lux) or green (wavelength: 525 nm; luminance: 20 lux) light for 5 days (8 hours per day). Joint nociception was assessed by von Frey hair algesiometry, dynamic weight bearing, and in vivo single unit extracellular recordings from knee joint mechanonociceptors. Compared to white light, GLT significantly reduced secondary mechanical hypersensitivity in both sexes and improved hindlimb weight bearing in females only. There was no effect of GLT on joint nociceptor activity in either sex. Serum lipidomics indicated an increase in circulating analgesic endolipids in response to GLT, particularly the N -acyl-glycines. Partial blockade of the endocannabinoid system with the G protein receptor-18/cannabinoid-1 receptor antagonist AM281 (500 μg/kg i.p.) attenuated GLT-induced analgesia. These data show for the first time that GLT acts to reduce OA pain by upregulating circulating analgesic endolipids, which then engage the endocannabinoid system.

BackgroundDifferent responses in human coronary arteries (HCA) and human middle meningeal arteries (HMMA) were observed for some of the novel CGRP receptor antagonists, the gepants, for inhibiting CGRP-induced relaxation. These differences could be explained by the presence of different receptor populations in the two vascular beds. Here, we aim to elucidate which receptors are involved in the relaxation to calcitonin gene-related peptide (CGRP), adrenomedullin (AM) and adrenomedullin 2 (AM2) in HCA and HMMA.MethodsRNA was isolated from homogenized human arteries (23 HCAs; 12 F, 11 M, age 50 ± 3 years and 26 HMMAs; 14 F, 12 M, age 51 ± 3 years) and qPCR was performed for different receptor subunits. Additionally, relaxation responses to CGRP, AM or AM2 of the human arteries were quantified using a Mulvany myograph system, in the presence or absence of the adrenomedullin 1 receptor antagonist AM22-52 and/or olcegepant.ResultsCalcitonin-like receptor (CLR) mRNA was expressed equally in both vascular beds, while calcitonin receptor (CTR) and receptor activity-modifying protein 3 (RAMP3) expression was low and could not be detected in all samples. RAMP1 expression was similar in HCA and HMMA, while RAMP2 expression was higher in HMMA. Moreover, receptor component protein (RCP) expression was higher in HMMA than in HCA. Functional experiments showed that olcegepant inhibits relaxation to all three agonists in both vascular beds. In HCA, antagonist AM22-52 did not inhibit relaxation to any of the agonists, while a trend for blocking relaxation to AM and AM2 could be observed in HMMA.ConclusionBased on the combined results from receptor subunit mRNA expression and the functional responses in both vascular tissues, relaxation of HCA is mainly mediated via the canonical CGRP receptor (CLR-RAMP1), while relaxation of HMMA can be mediated via both the canonical CGRP receptor and the adrenomedullin 1 receptor (CLR-RAMP2). Future research should investigate whether RAMP2 predominance over RAMP1 in the meningeal vasculature results in altered migraine susceptibility or in a different response to anti-migraine medication in these patients. Moreover, the exact role of RCP in CGRP receptor signalling should be elucidated in future research.

The underlying pathogenesis of chronic inflammatory pain is greatly complex, but the relevant therapies are still unavailable. Development of effective candidates for chronic inflammatory pain is highly urgent. We previously identified that trifluoro-icaritin (ICTF) exhibited a significant therapeutic activity against complete Freund's adjuvant (CFA)-induced chronic inflammatory pain, however, the precise mechanisms remain elusive. Here, the paw withdrawal threshold (PWT), paw withdrawal latency (PWL), and CatWalk gait analysis were used to determine the pain-related behaviors. The expression and co-localization of pain-related signaling molecules were detected by Western blot and immunofluorescence staining. Our results demonstrated that ICTF (3.0mg/kg, i.p.) effectively attenuated mechanical allodynia, thermal hyperalgesia and improved motor dysfunction induced by CFA, and the molecular docking displayed that CB2 receptor may be the therapeutic target of ICTF. Furthermore, ICTF not only up-regulated the levels of CB2 receptor, IL-10, β-endorphin and CD206, but also reduced the expression of P2Y12 receptor, NLRP3, ASC, Caspase-1, IL-1β, CD11b, and iNOS in the spinal cord of CFA rats. Additionally, the immunofluorescence staining from the spinal cord showed that ICTF significantly increased the co-expression between the microglial marker Iba-1 and CB2 receptor, IL-10, β-endorphin, respectively, but markedly decreased the co-localization between Iba-1 and P2Y12 receptor. Conversely, intrathecal administration of CB2 receptor antagonist AM630 dramatically reversed the inhibitory effects of ICTF on CFA-induced chronic inflammatory pain, leading to a promotion of pain hypersensitivity, abnormal gait parameters, microglial activation, and up-regulation of P2Y12 receptor and NLRP3 inflammasome, as well as the inhibition of CB2 receptor and IL-10/β-endorphin cascade. Taken together, these findings highlighted that ICTF alleviated CFA-induced neuroinflammation by enhancing CB2 receptor-mediated IL-10/β-endorphin signaling and suppressing microglial activation in the spinal cord, and uncovered that CB2 receptor may be exploited as a novel and promising target for ICTF treatment of chronic inflammatory pain.

Knee osteoarthritis (KOA) is a chronic degenerative bone metabolic disease that primarily affects older adults, leading to chronic pain and disability that affect patients' daily activities. Electroacupuncture (EA) is a commonly used method for the treatment of chronic pain in clinical practice. Previous studies indicate that the endocannabinoid system is involved in EA analgesia, but whether endocannabinopeptide VD-hemopressin (α) and RVD-hemopressin (α) derived from hemoglobin chains are involved in EA analgesia is unclear. RNA-seq technology was used to screen which genes involved in EA analgesia. The expression of hemoglobin α chain and 26S proteasome were determined by Western blotting. The level of VD-hemopressin (α) and RVD-hemopressin (α) were measured by UPLC-MS/MS. Microinjection VD-Hemopressin (α), RVD-Hemopressin (α) and 26S proteasome inhibitor MG-132 into vlPAG, then observe mechanical and thermal pain thresholds. Therefore, we used RNA-seq to obtain differentially expressed genes Hba-a1 and Hba-a2 involved in EA analgesia in the periaqueductal gray (PAG), which were translated into the hemoglobin α chain. EA significantly increased the expression of the hemoglobin α chain and the level of hemopressin (α) and RVD-hemopressin (α). Microinjection of VD-hemopressin (α) and RVD-hemopressin (α) into the ventrolateral periaqueductal gray (vlPAG) mimicked the analgesic effect of EA, while CB1 receptor antagonist AM251 reversed this effect. EA significantly increased the expression of 26S proteasome in KOA mice. Microinjection of 26S proteasome inhibitor MG132 before EA prevented both the anti-allodynic effect and upregulation of the concentration of RVD-hemopressin (α) by EA treatment and upregulated the expression of the hemoglobin α chain. Our data suggest that EA upregulated the concentration of VD-hemopressin (α) and RVD-hemopressin (α) through enhancement of the hemoglobin α chain degradation by 26S proteasome in the PAG, then activated the CB1 receptor, thereby exerting inhibition of chronic pain in a mouse model of KOA. These results provide new insights into the EA analgesic mechanisms and reveal possible targets for EA treatment of chronic pain.

Cardioprotective effect of CB1 receptor antagonist AM251 against β receptor-stimulated myocardial infarction via modulation of NF-kB signaling pathway in diabetic mice

Acute stress normally engages descending brain pathways to produce an antinociceptive response, known as stress-induced analgesia. Paradoxically, these descending pain modulatory pathways are also involved in the maintenance of the abnormal pain associated with chronic neuropathic pain. It remains unclear how stress-induced analgesia is affected by neuropathic pain states. We therefore examined the impact of a chronic constriction nerve-injury (CCI) model of neuropathic pain on restraint stress-induced analgesia in C57BL/6 mice. Thirty minutes of restraint stress produced analgesia in the hotplate thermal nociceptive assay that was less in CCI compared to control mice who underwent a sham-surgery. In sham but not CCI mice, stress-induced analgesia was reduced by the opioid receptor antagonist naltrexone. The cannabinoid CB1 receptor antagonist AM281 did not affect stress-induced analgesia in either sham or CCI mice. Low-dose pre-treatment with the dual fatty acid amide hydrolase and monoacylglycerol lipase inhibitor JZL195 increased stress-induced analgesia in CCI but not sham mice. The JZL195 enhancement of stress-induced analgesia in CCI mice was abolished by AM281 but was unaffected by naltrexone. These findings indicate that the acute opioid-mediated analgesic response to a psychological stressor is disrupted in a nerve-injury model of neuropathic pain. Importantly, this impairment of stress-induced analgesia was rescued by blockade of endocannabinoid breakdown via a cannabinoid CB1 receptor dependent mechanism. These findings suggest that subthreshold treatment with endocannabinoid degradation blockers could be used to alleviate the disruption of endogenous pain control systems in a neuropathic pain state.

The anesthetic drug, ketamine (KTM) has been shown to induce therapeutic effects against major depressive disorder (MDD), however the related underlying mechanisms remain unclear. In the present study, HT22 neuronal cells were treated with glutamate to imitate oxidative stress injury in MDD, and it was hypothesized that the cannabinoid type 1 (CB1) receptor mediates KTM-induced neuroprotection via ameliorating mitochondrial function in glutamate-treated neuronal cells. Compared with the control, glutamate decreased cell viability and intracellular antioxidants, including glutathione (GSH), catalase and superoxide dismutase 2 levels, and inhibited mitochondrial function simultaneously. Moreover, glutamate increased lactate dehydrogenase release, cellular apoptosis level, cleaved caspase-3 expression and intracellular oxidants, such as reactive oxygen species, oxidized GSH and mitochondrial superoxide in the cells. The presence of KTM, however, significantly decreased the glutamate-induced oxidative stress injury, ameliorated the antioxidant/oxidant levels in the cells, enhanced mitochondrial function and upregulated CB1 receptor expression (P<0.05). Co-administration of the CB1 receptor antagonist AM251 markedly abolished the KTM-induced cytoprotective effects and ameliorations of antioxidant/oxidant levels and mitochondrial function, and also reversed CB1 upregulation (P<0.05). These observations indicated that KTM decreases the oxidative stress injury caused by glutamate in HT22 neuronal cells, and the neuroprotective effects may be mediated by the CB1 receptor.

As wireless communication devices gain popularity, concerns about the potential risks of environmental exposure to complex frequency electromagnetic radiation (EMR) on mental health have become a public health issue. Historically, EMR research has predominantly focused on single- frequency electromagnetic waves, neglecting the study of multi-frequency electromagnetic waves, which more accurately represent everyday life. To address these concerns, our study compared the emotional effects of single-frequency and dual-frequency EMR while exploring potential molecular mechanisms and intervention targets. Our results revealed that single-frequency EMR at 2.65 or 0.8 GHz did not induce anxiety-like behavior in mice. However, exposure to dual-frequency EMR at 2.65/0.8 GHz significantly led to anxiety-like behavior in mice. Further analysis of mouse sera revealed substantial increases in corticosterone and corticotrophin releasing hormone levels following exposure to 2.65/0.8 GHz EMR. Transcriptome sequencing indicated a significant decrease in the expression of Cnr1, encoding cannabinoid receptor 1 Type (CB1R), in the cerebral. This finding was consistently verified through western blot analysis, revealing a substantial reduction in CB1R content. Additionally, a significant decrease in the endocannabinoid 2-arachidonoylglycerol was observed in the cerebral cortex. Remarkably, administering the cannabinoid receptor agonist Win55-212-2 significantly alleviated the anxiety-like behavior, and the cannabinoid receptor antagonist AM251 effectively counteracted the anti-anxiety effects of Win55-212-2. In summary, our research confirmed that dual-frequency EMR is more likely to induce anxiety-like behavior in mice than single-frequency EMR, with implications for the hypothalamic-pituitary-adrenal axis and the endocannabinoid system. Furthermore, our findings suggest that Win55-212-2 may represent a novel avenue for researching and developing anti-EMR drugs.

Microglia and macrophages can influence the evolution of myelin lesions through the production of extracellular vesicles (EVs). While microglial EVs promote in vitro differentiation of oligodendrocyte precursor cells (OPCs), whether EVs derived from macrophages aid or limit OPC maturation is unknown. Immunofluorescence analysis for the myelin protein MBP was employed to evaluate the impact of EVs from primary rat macrophages on cultured OPC differentiation. Raman spectroscopy and liquid chromatography-mass spectrometry was used to define the promyelinating lipid components of myelin EVs obtained in vitro and isolated from human plasma. Here we show that macrophage-derived EVs do not promote OPC differentiation, and those released from macrophages polarized towards an inflammatory state inhibit OPC maturation. However, their lipid cargo promotes OPC maturation in a similar manner to microglial EVs. We identify the promyelinating endocannabinoids anandamide and 2-arachidonoylglycerol in EVs released by both macrophages and microglia in vitro and circulating in human plasma. Analysis of OPC differentiation in the presence of the endocannabinoid receptor antagonists SR141716A and AM630 reveals a key role of vesicular endocannabinoids in OPC maturation. From this study, EV-associated endocannabinoids emerge as important mediators in microglia/macrophage-oligodendrocyte crosstalk, which may be exploited to enhance myelin repair.