Myeloid cannabinoid CB1 receptor deletion confers atheroprotection in male mice by reducing macrophage proliferation in a sex-dependent manner.

AIMS: Although the cannabinoid CB1 receptor has been implicated in atherosclerosis, its cell-specific effects in this disease are not well understood. To address this, we generated a transgenic mouse model to study the role of myeloid CB1 signaling in atherosclerosis. METHODS AND RESULTS: Here, we report that male mice with myeloid-specific Cnr1 deficiency on atherogenic background developed smaller lesions and necrotic cores than controls, while only minor genotype differences were observed in females. Male Cnr1 deficient mice showed reduced arterial monocyte recruitment and macrophage proliferation with less inflammatory phenotype. The sex-specific differences in proliferation were dependent on estrogen receptor (ER)α-estradiol signaling. Kinase activity profiling identified a CB1-dependent regulation of p53 and cyclin-dependent kinases. Transcriptomic profiling further revealed chromatin modifications, mRNA processing and mitochondrial respiration among the key processes affected by CB1 signaling, which was supported by metabolic flux assays. Chronic administration of the peripherally-restricted CB1 antagonist JD5037 inhibited plaque progression and macrophage proliferation, but only in male mice. Finally, CNR1 expression was detectable in human carotid endarterectomy plaques and inversely correlated with proliferation, oxidative metabolism and inflammatory markers, suggesting a possible implication of CB1-dependent regulation in human pathophysiology. CONCLUSION: Impaired macrophage CB1 signaling is atheroprotective by limiting their arterial recruitment, proliferation and inflammatory reprogramming in male mice. The importance of macrophage CB1 signaling appears to be sex-dependent.

Leveraging interindividual variability in threat conditioning of inbred mice to model trait anxiety.

Trait anxiety is a major risk factor for stress-induced and anxiety disorders in humans. However, animal models accounting for the interindividual variability in stress vulnerability are largely lacking. Moreover, the pervasive bias of using mostly male animals in preclinical studies poorly reflects the increased prevalence of psychiatric disorders in women. Using the threat imminence continuum theory, we designed and validated an auditory aversive conditioning-based pipeline in both female and male mice. We operationalised trait anxiety by harnessing the naturally occurring variability of defensive freezing responses combined with a model-based clustering strategy. While sustained freezing during prolonged retrieval sessions was identified as an anxiety-endophenotype biomarker in both sexes, females were consistently associated with an increased freezing response. RNA-sequencing of CeA, BLA, ACC, and BNST revealed massive differences in phasic and sustained responders' transcriptomes, correlating with transcriptomic signatures of psychiatric disorders, particularly post-traumatic stress disorder (PTSD). Moreover, we detected significant alterations in the excitation/inhibition balance of principal neurons in the lateral amygdala. These findings provide compelling evidence that trait anxiety in inbred mice can be leveraged to develop translationally relevant preclinical models to investigate mechanisms of stress susceptibility in a sex-specific manner.

Long non-coding RNAs expression and regulation across different brain regions in primates.

Human and non-human primates have strikingly similar genomes, but they strongly differ in many brain-based processes (e.g., behaviour and cognition). While the functions of protein-coding genes have been extensively studied, rather little is known about the role of non-coding RNAs such as long non-coding RNAs (lncRNAs). Here, we predicted lncRNAs and analysed their expression pattern across different brain regions of human and non-human primates (chimpanzee, gorilla, and gibbon). Our analysis identified shared orthologous and non-orthologous lncRNAs, showing striking differences in the genomic features. Differential expression analysis of the shared orthologous lncRNAs from humans and chimpanzees revealed distinct expression patterns in subcortical regions (striatum, hippocampus) and neocortical areas while retaining a homogeneous expression in the cerebellum. Co-expression analysis of lncRNAs and protein-coding genes revealed massive proportions of co-expressed pairs in neocortical regions of humans compared to chimpanzees. Network analysis of co-expressed pairs revealed the distinctive role of the hub-acting orthologous lncRNAs in a region- and species-specific manner. Overall, our study provides novel insight into lncRNA driven gene regulatory landscape, neural regulation, brain evolution, and constitutes a resource for primate's brain lncRNAs.

Local cannabinoid receptor type-1 regulates glial cell activity and insulin-like growth factor-1 receptor signaling in the mediobasal hypothalamus.

As organisms age, the activity of the endocannabinoid system in the brain declines, coinciding with increased neuroinflammation and disrupted hypothalamic functions. Notably, cannabinoid receptors type-1 (CB1) are highly expressed in the ventromedial hypothalamic nucleus (VMH) within the mediobasal hypothalamus, a central area of neuroendocrine regulation. This study investigates whether the CB1 receptor influences age-related changes in a brain region-dependent manner. Therefore, we performed stereotaxic injections of rAAV1/2 expressing Cre recombinase in 2-month-old CB1flox/flox male animals to delete the CB1 gene and in CB1-deficient (CB1-STOP) mice to induce its re-expression. The intensity of pro-inflammatory glial activity, gonadotropin-releasing hormone (GnRH) and insulin-like growth factor-1 receptor (IGF-1R) expression was assessed in the hypothalamus of mice at 18-19 months of age. Site-specific CB1 receptor deletion induced pro-inflammatory glial activity and increased hypothalamic Igf1r mRNA expression. Unexpectedly, GnRH levels remained unaltered. Importantly, rescuing the receptor in null mutant animals had the opposite effect: it reduced pro-inflammatory glial activation and decreased Igf1r mRNA expression without affecting GnRH production. Overall, the study highlights the important role of the CB1 receptor in the VMH in reducing age-related inflammation and modulating IGF-1R signaling.

Cannabinoid type-1 receptor signaling in dopaminergic Engrailed-1 expressing neurons modulates motivation and depressive-like behavior.

The endocannabinoid system comprises highly versatile signaling functions within the nervous system. It is reported to modulate the release of several neurotransmitters, consequently affecting the activity of neuronal circuits. Investigations have highlighted its roles in numerous processes, including appetite-stimulating characteristics, particularly for palatable food. Moreover, endocannabinoids are shown to fine-tune dopamine-signaled processes governing motivated behavior. Specifically, it has been demonstrated that excitatory and inhibitory inputs controlled by the cannabinoid type 1 receptor (CB1) regulate dopaminergic neurons in the mesocorticolimbic pathway. In the present study, we show that mesencephalic dopaminergic (mesDA) neurons in the ventral tegmental area (VTA) express CB1, and we investigated the consequences of specific deletion of CB1 in cells expressing the transcription factor Engrailed-1 (En1). To this end, we validated a new genetic mouse line EN1-CB1-KO, which displays a CB1 knockout in mesDA neurons beginning from their differentiation, as a tool to elucidate the functional contribution of CB1 in mesDA neurons. We revealed that EN1-CB1-KO mice display a significantly increased immobility time and shortened latency to the first immobility in the forced swim test of adult mice. Moreover, the maximal effort exerted to obtain access to chocolate-flavored pellets was significantly reduced under a progressive ratio schedule. In contrast, these mice do not differ in motor skills, anhedonia- or anxiety-like behavior compared to wild-type littermates. Taken together, these findings suggest a depressive-like or despair behavior in an inevitable situation and a lack of motivation to seek palatable food in EN1-CB1-KO mice, leading us to propose that CB1 plays an important role in the physiological functions of mesDA neurons. In particular, our data suggest that CB1 directly modifies the mesocorticolimbic pathway implicated in depressive-like/despair behavior and motivation. In contrast, the nigrostriatal pathway controlling voluntary movement seems to be unaffected.

Chronic Administration of Δ9-Tetrahydrocannabinol Alters Brain Glucose Uptake and Improves Waiting Impulsivity in the Rat.

Introduction: Δ9-Tetrahydrocannabinol (THC) acts as an agonist at cannabinoid receptors. Its chronic intake affects many behaviors, including cognitive processes. The aims of this study in rats are to assess the chronic effects of THC on impulsivity and on regional brain glucose uptake. Materials and Methods: For the determination of "waiting impulsivity," a total of 20 male Lister Hooded rats were trained to perform a reaction time task, followed by a baseline test of impulsivity and baseline glucose uptake measurements with [18F]-fluoro-2-deoxy-D-glucose and positron emission tomography (PET). Then, 10 rats each received 3 mg/kg THC or vehicle injected intraperitoneally daily for 21 days. Subsequently, a second behavioral test and PET measurements were performed, and blood THC concentrations were determined. Analyses of variance of brain regions of the impulsivity network with the parameter "standardized uptake value" regarding glucose uptake and correlation analyses of the collected parameters were carried out. Discussion: After chronic THC treatment, decreased glucose uptake (p-values <0.05) was found in cingulate cortex, hippocampus, amygdala, thalamus, and cerebellar cortex, as compared with vehicle-treated rats. The number of correct no-go responses (increased waiting time) significantly increased (p<0.05) in THC-treated rats. Furthermore, correct no-go responses correlated positively and strongly with the THC blood concentrations (Spearman's ρ=0.79, p<0.01). Conclusion: These findings reflect a specific reduction in impulsive behavior after chronic THC treatment, showing a functionally relevant influence of THC on "waiting impulsivity" with reduced selective glucose uptake at the same time.

Microglial cannabinoid receptor type 1 mediates social memory deficits in mice produced by adolescent THC exposure and 16p11.2 duplication.

Adolescent cannabis use increases the risk for cognitive impairments and psychiatric disorders. Cannabinoid receptor type 1 (Cnr1) is expressed not only in neurons and astrocytes, but also in microglia, which shape synaptic connections during adolescence. However, the role of microglia in mediating the adverse cognitive effects of delta-9-tetrahydrocannabinol (THC), the principal psychoactive constituent of cannabis, is not fully understood. Here, we report that in mice, adolescent THC exposure produces microglial apoptosis in the medial prefrontal cortex (mPFC), which was exacerbated in a model of 16p11.2 duplication, a representative copy number variation (CNV) risk factor for psychiatric disorders. These effects are mediated by microglial Cnr1, leading to reduction in the excitability of mPFC pyramidal-tract neurons and deficits in social memory in adulthood. Our findings suggest the microglial Cnr1 may contribute to adverse effect of cannabis exposure in genetically vulnerable individuals.

Microglial cannabinoid receptor type 1 mediates social memory deficits produced by adolescent THC exposure and 16p11.2 duplication.

Adolescent cannabis use increases the risk for cognitive impairments and psychiatric disorders. Cannabinoid receptor type 1 (Cnr1) is expressed not only in neurons and astrocytes, but also in microglia, which shape synaptic connections during adolescence. Nonetheless, until now, the role of microglia in mediating the adverse cognitive effects of delta-9-tetrahydrocannabinol (THC), the principal psychoactive constituent of cannabis, has been unexplored. Here, we report that adolescent THC exposure produces microglial apoptosis in the medial prefrontal cortex (mPFC), which was exacerbated in the mouse model of 16p11.2 duplication, a representative copy number variation (CNV) risk factor for psychiatric disorders. These effects are mediated by microglial Cnr1, leading to reduction in the excitability of mPFC pyramidal-tract neurons and deficits in social memory in adulthood. Our findings highlight the importance of microglial Cnr1 to produce the adverse effect of cannabis exposure in genetically vulnerable individuals.

NAPE-PLD deletion in stress-TRAPed neurons results in an anxiogenic phenotype.

Anandamide (AEA) is an endogenous ligand of the cannabinoid CB1 and CB2 receptors, being a component of the endocannabinoid signaling system, which supports the maintenance or regaining of neural homeostasis upon internal and external challenges. AEA is thought to play a protective role against the development of pathological states after prolonged stress exposure, including depression and generalized anxiety disorder. Here, we used the chronic social defeat (CSD) stress as an ethologically valid model of chronic stress in male mice. We characterized a genetically modified mouse line where AEA signaling was reduced by deletion of the gene encoding the AEA synthesizing enzyme N-acyl-phosphatidylethanolamine-hydrolyzing phospholipase D (NAPE-PLD) specifically in neurons activated at the time of CSD stress. One week after the stress, the phenotype was assessed in behavioral tests and by molecular analyses. We found that NAPE-PLD deficiency in neurons activated during the last three days of CSD stress led to an increased anxiety-like behavior. Investigating the molecular mechanisms underlying this phenotype may suggest three main altered pathways to be affected: (i) desensitization of the negative feedback loop of the hypothalamic-pituitary-adrenal axis, (ii) disinhibition of the amygdala by the prefrontal cortex, and (iii) altered neuroplasticity in the hippocampus and prefrontal cortex.

Nuclei on the Rise: When Nuclei-Based Methods Meet Next-Generation Sequencing.

In the last decade, we have witnessed an upsurge in nuclei-based studies, particularly coupled with next-generation sequencing. Such studies aim at understanding the molecular states that exist in heterogeneous cell populations by applying increasingly more affordable sequencing approaches, in addition to optimized methodologies developed to isolate and select nuclei. Although these powerful new methods promise unprecedented insights, it is important to understand and critically consider the associated challenges. Here, we provide a comprehensive overview of the rise of nuclei-based studies and elaborate on their advantages and disadvantages, with a specific focus on their utility for transcriptomic sequencing analyses. Improved designs and appropriate use of the various experimental strategies will result in acquiring biologically accurate and meaningful information.

Mitochondrial cannabinoid receptors gate corticosterone impact on novel object recognition.

Corticosteroid-mediated stress responses require the activation of complex brain circuits involving mitochondrial activity, but the underlying cellular and molecular mechanisms are scantly known. The endocannabinoid system is implicated in stress coping, and it can directly regulate brain mitochondrial functions via type 1 cannabinoid (CB1) receptors associated with mitochondrial membranes (mtCB1). In this study, we show that the impairing effect of corticosterone in the novel object recognition (NOR) task in mice requires mtCB1 receptors and the regulation of mitochondrial calcium levels in neurons. Different brain circuits are modulated by this mechanism to mediate the impact of corticosterone during specific phases of the task. Thus, whereas corticosterone recruits mtCB1 receptors in noradrenergic neurons to impair NOR consolidation, mtCB1 receptors in local hippocampal GABAergic interneurons are required to inhibit NOR retrieval. These data reveal unforeseen mechanisms mediating the effects of corticosteroids during different phases of NOR, involving mitochondrial calcium alterations in different brain circuits.

Peripheral CB1 receptor blockade acts as a memory enhancer through a noradrenergic mechanism.

Peripheral inputs continuously shape brain function and can influence memory acquisition, but the underlying mechanisms have not been fully understood. Cannabinoid type-1 receptor (CB1R) is a well-recognized player in memory performance, and its systemic modulation significantly influences memory function. By assessing low arousal/non-emotional recognition memory in mice, we found a relevant role of peripheral CB1R in memory persistence. Indeed, the peripherally-restricted CB1R specific antagonist AM6545 showed significant mnemonic effects that were occluded in adrenalectomized mice, and after peripheral adrenergic blockade. AM6545 also transiently impaired contextual fear memory extinction. Vagus nerve chemogenetic inhibition reduced AM6545-induced mnemonic effect. Genetic CB1R deletion in dopamine ß-hydroxylase-expressing cells enhanced recognition memory persistence. These observations support a role of peripheral CB1R modulating adrenergic tone relevant for cognition. Furthermore, AM6545 acutely improved brain connectivity and enhanced extracellular hippocampal norepinephrine. In agreement, intra-hippocampal ß-adrenergic blockade prevented AM6545 mnemonic effects. Altogether, we disclose a novel CB1R-dependent peripheral mechanism with implications relevant for lengthening the duration of non-emotional memory.

Myeloid But Not Endothelial Expression of the CB2 Receptor Promotes Atherogenesis in the Context of Elevated Levels of the Endocannabinoid 2-Arachidonoylglycerol.

The endocannabinoid 2-arachidonoylglycerol (2-AG) is an inflammatory mediator and ligand for the cannabinoid receptors CB1 and CB2. We investigated the atherogenic mechanisms set in motion by 2-AG. Therefore, we created two atherosclerotic mouse models with distinct cell-specific knockouts of the CB2 receptor on either myeloid or endothelial cells. These mice were treated with JZL184, resulting in elevated plasma levels of 2-AG. After a high-fat high-cholesterol diet, atherosclerotic plaques were analyzed. The atherogenic effect of 2-AG was abrogated in mice lacking myeloid expression of the CB2 receptor but not in mice lacking endothelial expression of the CB2 receptor. In vitro, treatment of human monocytes with 2-AG led to the increased production of reactive oxygen species (ROS) and IL-1ß. In conclusion, 2-AG shows an atherogenic effect in vivo, dependent on the presence of the CB2 receptor on myeloid cells. In addition, our in vitro data revealed 2-AG to promote inflammatory signalling in monocytes. 2-Arachidonoylglycerol shows an atherogenic effect that is abrogated in mice lacking myeloid expression of the CB2 receptor.

Extraction and Simultaneous Quantification of Endocannabinoids and Endocannabinoid-Like Lipids in Biological Tissues.

Extraction and quantification of endocannabinoids from biological tissues is essential to unravel their changes under physiological and pathophysiological conditions. We describe here an analytical protocol for the extraction of endocannabinoids, anandamide (archidonoyl ethanolamide, AEA) and 2-arachidonoyl glycerol (2-AG), and endocannabinoid-like lipids such as palmitoyl ethanolamide (PEA) and oleoyl ethanolamide (OEA), as well as arachidonic acid (AA) from biological tissues using liquid-liquid extraction method and simultaneous quantification by liquid chromatography multiple reaction monitoring (LC/MRM).

A Resilience Related Glial-Neurovascular Network Is Transcriptionally Activated after Chronic Social Defeat in Male Mice.

Upon chronic stress, a fraction of individuals shows stress resilience, which can prevent long-term mental dysfunction. The underlying molecular mechanisms are complex and have not yet been fully understood. In this study, we performed a data-driven behavioural stratification together with single-cell transcriptomics of the hippocampus in a mouse model of chronic social defeat stress. Our work revealed that in a sub-group exhibiting molecular responses upon chronic stress, the dorsal hippocampus is particularly involved in neuroimmune responses, angiogenesis, myelination, and neurogenesis, thereby enabling brain restoration and homeostasis after chronic stress. Based on these molecular insights, we applied rapamycin after the stress as a proof-of-concept pharmacological intervention and were able to substantially increase stress resilience. Our findings serve as a data resource and can open new avenues for further understanding of molecular processes underlying stress response and for targeted interventions supporting resilience.

Cannabinoid CB1 Receptor Deletion from Catecholaminergic Neurons Protects from Diet-Induced Obesity.

High-calorie diets and chronic stress are major contributors to the development of obesity and metabolic disorders. These two risk factors regulate the activity of the sympathetic nervous system (SNS). The present study showed a key role of the cannabinoid type 1 receptor (CB1) in dopamine ß-hydroxylase (dbh)-expressing cells in the regulation of SNS activity. In a diet-induced obesity model, CB1 deletion from these cells protected mice from diet-induced weight gain by increasing sympathetic drive, resulting in reduced adipogenesis in white adipose tissue and enhanced thermogenesis in brown adipose tissue. The deletion of CB1 from catecholaminergic neurons increased the plasma norepinephrine levels, norepinephrine turnover, and sympathetic activity in the visceral fat, which coincided with lowered neuropeptide Y (NPY) levels in the visceral fat of the mutant mice compared with the controls. Furthermore, the mutant mice showed decreased plasma corticosterone levels. Our study provided new insight into the mechanisms underlying the roles of the endocannabinoid system in regulating energy balance, where the CB1 deletion in dbh-positive cells protected from diet-induced weight gain via multiple mechanisms, such as increased SNS activity, reduced NPY activity, and decreased basal hypothalamic-pituitary-adrenal (HPA) axis activity.

Association of polygenic risk scores and hair cortisol with mental health trajectories during COVID lockdown.

The COVID-19 pandemic is a global stressor with inter-individually differing influences on mental health trajectories. Polygenic Risk Scores (PRSs) for psychiatric phenotypes are associated with individual mental health predispositions. Elevated hair cortisol concentrations (HCC) and high PRSs are related to negative mental health outcomes. We analyzed whether PRSs and HCC are related to different mental health trajectories during the first COVID lockdown in Germany. Among 523 participants selected from the longitudinal resilience assessment study (LORA), we previously reported three subgroups (acute dysfunction, delayed dysfunction, resilient) based on weekly mental health (GHQ-28) assessment during COVID lockdown. DNA from blood was collected at the baseline of the original LORA study (n = 364) and used to calculate the PRSs of 12 different psychopathological phenotypes. An explorative bifactor model with Schmid-Leiman transformation was calculated to extract a general genetic factor for psychiatric disorders. Hair samples were collected quarterly prior to the pandemic for determining HCC (n = 192). Bivariate logistic regressions were performed to test the associations of HCC and the PRS factors with the reported trajectories. The bifactor model revealed 1 general factor and 4 sub-factors. Results indicate a significant association between increased values on the general risk factor and the allocation to the acute dysfunction class. The same was found for elevated HCC and the exploratorily tested sub-factor "childhood-onset neurodevelopmental disorders". Genetic risk and long-term cortisol secretion as a potential indicator of stress, indicated by PRSs and HCC, respectively, predicted different mental health trajectories. Results indicate a potential for future studies on risk prediction.

Dynamic Changes in the Endocannabinoid System during the Aging Process: Focus on the Middle-Age Crisis.

Endocannabinoid (eCB) signaling is markedly decreased in the hippocampus (Hip) of aged mice, and the genetic deletion of the cannabinoid receptor type 1 (CB1) leads to an early onset of cognitive decline and age-related histological changes in the brain. Thus, it is hypothesized that cognitive aging is modulated by eCB signaling through CB1. In the present study, we detailed the changes in the eCB system during the aging process using different complementary techniques in mouse brains of five different age groups, ranging from adolescence to old age. Our findings indicate that the eCB system is most strongly affected in middle-aged mice (between 9 and 12 months of age) in a brain region-specific manner. We show that 2-arachidonoylglycerol (2-AG) was prominently decreased in the Hip and moderately in caudate putamen (CPu), whereas anandamide (AEA) was decreased in both CPu and medial prefrontal cortex along with cingulate cortex (mPFC+Cg), starting from 6 months until 12 months. Consistent with the changes in 2-AG, the 2-AG synthesizing enzyme diacylglycerol lipase α (DAGLα) was also prominently decreased across the sub-regions of the Hip. Interestingly, we found a transient increase in CB1 immunoreactivity across the sub-regions of the Hip at 9 months, a plausible compensation for reduced 2-AG, which ultimately decreased strongly at 12 months. Furthermore, quantitative autoradiography of CB1 revealed that [3H]CP55940 binding markedly increased in the Hip at 9 months. However, unlike the protein levels, CB1 binding density did not drop strongly at 12 months and at old age. Furthermore, [3H]CP55940 binding was significantly increased in the lateral entorhinal cortex (LEnt), starting from the middle age until the old age. Altogether, our findings clearly indicate a middle-age crisis in the eCB system, which could be a potential time window for therapeutic interventions to abrogate the course of cognitive aging.

Brain-derived neurotrophic factor expression in serotonergic neurons improves stress resilience and promotes adult hippocampal neurogenesis.

The neurotrophin brain-derived neurotrophic factor (BDNF) stimulates adult neurogenesis, but also influences structural plasticity and function of serotonergic neurons. Both, BDNF/TrkB signaling and the serotonergic system modulate behavioral responses to stress and can lead to pathological states when dysregulated. The two systems have been shown to mediate the therapeutic effect of antidepressant drugs and to regulate hippocampal neurogenesis. To elucidate the interplay of both systems at cellular and behavioral levels, we generated a transgenic mouse line that overexpresses BDNF in serotonergic neurons in an inducible manner. Besides displaying enhanced hippocampus-dependent contextual learning, transgenic mice were less affected by chronic social defeat stress (CSDS) compared to wild-type animals. In parallel, we observed enhanced serotonergic axonal sprouting in the dentate gyrus and increased neural stem/progenitor cell proliferation, which was uniformly distributed along the dorsoventral axis of the hippocampus. In the forced swim test, BDNF-overexpressing mice behaved similarly as wild-type mice treated with the antidepressant fluoxetine. Our data suggest that BDNF released from serotonergic projections exerts this effect partly by enhancing adult neurogenesis. Furthermore, independently of the genotype, enhanced neurogenesis positively correlated with the social interaction time after the CSDS, a measure for stress resilience.

Cannabinoid CB1 receptor gene inactivation in oligodendrocyte precursors disrupts oligodendrogenesis and myelination in mice.

Cannabinoids are known to modulate oligodendrogenesis and developmental CNS myelination. However, the cell-autonomous action of these compounds on oligodendroglial cells in vivo, and the molecular mechanisms underlying these effects have not yet been studied. Here, by using oligodendroglial precursor cell (OPC)-targeted genetic mouse models, we show that cannabinoid CB1 receptors exert an essential role in modulating OPC differentiation at the critical periods of postnatal myelination. We found that selective genetic inactivation of CB1 receptors in OPCs in vivo perturbs oligodendrogenesis and postnatal myelination by altering the RhoA/ROCK signaling pathway, leading to hypomyelination, and motor and cognitive alterations in young adult mice. Conversely, pharmacological CB1 receptor activation, by inducing E3 ubiquitin ligase-dependent RhoA proteasomal degradation, promotes oligodendrocyte development and CNS myelination in OPCs, an effect that was not evident in OPC-specific CB1 receptor-deficient mice. Moreover, pharmacological inactivation of ROCK in vivo overcomes the defects in oligodendrogenesis and CNS myelination, and behavioral alterations found in OPC-specific CB1 receptor-deficient mice. Overall, this study supports a cell-autonomous role for CB1 receptors in modulating oligodendrogenesis in vivo, which may have a profound impact on the scientific knowledge and therapeutic manipulation of CNS myelination by cannabinoids.