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The reticular thalamic nucleus (RTN) is a thin shell that covers the dorsal thalamus and controls the overall information flow from the thalamus to the cerebral cortex through GABAergic projections that contact thalamo-cortical neurons (TC). RTN neurons receive glutamatergic afferents fibers from neurons of the sixth layer of the cerebral cortex and from TC collaterals. The firing mode of RTN neurons facilitates the generation of sleep–wake cycles; a tonic mode or desynchronized mode occurs during wake and REM sleep and a burst-firing mode or synchronized mode is associated with deep sleep. Despite the presence of cannabinoid receptors CB1 (CB1Rs) and mRNA that encodes these receptors in RTN neurons, there are few works that have analyzed the participation of endocannabinoid-mediated transmission on the electrical activity of RTN. Here, we locally blocked or activated CB1Rs in ketamine anesthetized rats to analyze the spontaneous extracellular spiking activity of RTN neurons. Our results show the presence of a tonic endocannabinoid input, since local infusion of AM 251, an antagonist/inverse agonist, modifies RTN neurons electrical activity; furthermore, local activation of CB1Rs by anandamide or WIN 55212-2 produces heterogeneous effects in the basal spontaneous spiking activity, where the main effect is an increase in the spiking rate accompanied by a decrease in bursting activity in a dose-dependent manner; this effect is inhibited by AM 251. In addition, previous activation of GABA-A receptors suppresses the effects of CB1Rs on reticular neurons. Our results show that local activation of CB1Rs primarily diminishes the burst firing mode of RTn neurons. [ABSTRACT FROM AUTHOR]

Hypofunctioning of NMDA receptors, and the resulting shift in the balance between excitation and inhibition, is considered a key process in the pathophysiology of schizophrenia. One important manifestation of this phenomenon is changes in neural oscillations, those above 30 Hz (i.e., gamma-band oscillations), in particular. Although both preclinical and clinical studies observed increased gamma activity following acute administration of NMDA receptor antagonists, the relevance of this phenomenon has been recently questioned given the reduced gamma oscillations typically observed during sensory and cognitive tasks in schizophrenia. However, there is emerging, yet contradictory, evidence for increased spontaneous gamma-band activity (i.e., at rest or under baseline conditions). Here, we use the sub-chronic phencyclidine (PCP) rat model for schizophrenia, which has been argued to model the pathophysiology of schizophrenia more closely than acute NMDA antagonism, to investigate gamma oscillations (30–100 Hz) in the medial prefrontal cortex of anesthetized animals. While baseline gamma oscillations were not affected, oscillations induced by train stimulation of the posterior dorsal CA1 (pdCA1) field of the hippocampus were enhanced in PCP-treated animals (5 mg/kg, twice daily for 7 days, followed by a 7-day washout period). This effect was reversed by pharmacological enhancement of endocannabinoid levels via systemic administration of URB597 (0.3 mg/kg), an inhibitor of the catabolic enzyme of the endocannabinoid anandamide. Intriguingly, the pharmacological blockade of CB1 receptors by AM251 unmasked a reduced gamma oscillatory activity in PCP-treated animals. The findings are consistent with the observed effects of URB597 and AM251 on behavioral deficits reminiscent of the symptoms of schizophrenia and further validate the potential for cannabinoid-based drugs as a treatment for schizophrenia. [ABSTRACT FROM AUTHOR]

The brain requires large quantities of energy to sustain its functions. At the same time, the brain is isolated from the rest of the body, forcing this organ to develop strategies to control and fulfill its own energy needs. Likely based on these constraints, several brain-specific mechanisms emerged during evolution. For example, metabolically specialized cells are present in the brain, where intercellular metabolic cycles are organized to separate workload and optimize the use of energy. To orchestrate these strategies across time and space, several signaling pathways control the metabolism of brain cells. One of such controlling systems is the endocannabinoid system, whose main signaling hub in the brain is the type-1 cannabinoid (CB1) receptor. CB1 receptors govern a plethora of different processes in the brain, including cognitive function, emotional responses, or feeding behaviors. Classically, the mechanisms of action of CB1 receptors on brain function had been explained by its direct targeting of neuronal synaptic function. However, new discoveries have challenged this view. In this review, we will present and discuss recent data about how a small fraction of CB1 receptors associated to mitochondrial membranes (mtCB1), are able to exert a powerful control on brain functions and behavior. mtCB1 receptors impair mitochondrial functions both in neurons and astrocytes. In the latter cells, this effect is linked to an impairment of astrocyte glycolytic function, resulting in specific behavioral outputs. Finally, we will discuss the potential implications of (mt)CB1 expression on oligodendrocytes and microglia metabolic functions, with the aim to encourage interdisciplinary approaches to better understand the role of (mt)CB1 receptors in brain function and behavior. [ABSTRACT FROM AUTHOR]

Addiction to psychostimulant drugs, such as cocaine, D-amphetamine, and methamphetamine, is a public health issue that substantially contributes to the global burden of disease. Psychostimulant drugs promote an increase in dopamine levels within the mesocorticolimbic system, which is central to the rewarding properties of such drugs. Cannabinoid receptors (CB1R and CB2R) are expressed in the main areas of this system and implicated in the neuronal mechanisms underlying the rewarding effect of psychostimulant drugs. Here, we reviewed studies focusing on pharmacological intervention targeting cannabinoid CB1R and CB2R and their interaction in the modulation of psychostimulant responses. [ABSTRACT FROM AUTHOR]

The endocannabinoid system, with its intricate presence in numerous cells, tissues, and organs, offers a compelling avenue for therapeutic interventions. Central to this system are the cannabinoid receptors 1 and 2 (CB1R and CB2R), whose ubiquity can introduce complexities in targeted treatments due to their wide-ranging physiological influence. Injuries to the central nervous system (CNS), including strokes and traumatic brain injuries, induce localized pro-inflammatory immune responses, termed neuroinflammation. Research has shown that compensatory immunodepression usually follows, and these mechanisms might influence immunity, potentially affecting infection risks in patients. As traditional preventive treatments like antibiotics face challenges, the exploration of immunomodulatory therapies offers a promising alternative. This review delves into the potential neuroprotective roles of the cannabinoid receptors: CB1R's involvement in mitigating excitotoxicity and CB2R's dual role in promoting cell survival and anti-inflammatory responses. However, the potential of cannabinoids to reduce neuroinflammation must be weighed against the risk of exacerbating immunodepression. Though the endocannabinoid system promises numerous therapeutic benefits, understanding its multifaceted signaling mechanisms and outcomes remains a challenge. [ABSTRACT FROM AUTHOR]

Objective(s): Gentamicin-induced nephrotoxicity was used as an experimental model of kidney disease. The present study was performed to assess the therapeutic role of cannabidiol (CBD) against gentamicin-induced renal damage. Materials and Methods: Forty two male Wistar rats were randomly allocated into 6 groups (n=7), including: (1) Control, (2) Vehicle, (3) Gentamicin-treated group (100 mg/kg/day) for 10 days (GM), (4-6) 3 Gentamicin-CBD-treated groups (2.5, 5, and 10 mg/kg/day) for 10 days (GM+CBD2.5, GM+CBD5, GM+CBD10). Serum levels of BUN and Cr, renal histology as well as real-time qRT-PCR were used to investigate the pattern of changes at different levels.Results: Gentamicin increased serum BUN and Cr (P

Background and Purpose: Cannabinoids are a promising therapeutic avenue for chronic pain. However, clinical trials often fail to report analgesic efficacy of cannabinoids. Inhibition of voltage gate calcium (Cav) channels is one mechanism through which cannabinoids may produce analgesia. We hypothesized that cannabinoids and cannabinoid receptor agonists target different types of Cav channels through distinct mechanisms. Experimental Approach: Electrophysiological recordings from tsA‐201 cells expressing either Cav3.2 or Cav2.2 were used to assess inhibition by HU‐210 or cannabidiol (CBD) in the absence and presence of the CB1 receptor. Homology modelling assessed potential interaction sites for CBD in both Cav2.2 and Cav3.2. Analgesic effects of CBD were assessed in mouse models of inflammatory and neuropathic pain. Key Results: HU‐210 (1 μM) inhibited Cav2.2 function in the presence of CB1 receptor but had no effect on Cav3.2 regardless of co‐expression of CB1 receptor. By contrast, CBD (3 μM) produced no inhibition of Cav2.2 and instead inhibited Cav3.2 independently of CB1 receptors. Homology modelling supported these findings, indicating that CBD binds to and occludes the pore of Cav3.2, but not Cav2.2. Intrathecal CBD alleviated thermal and mechanical hypersensitivity in both male and female mice, and this effect was absent in Cav3.2 null mice. Conclusion and Implications: Our findings reveal differential modulation of Cav2.2 and Cav3.2 channels by CB1 receptors and CBD. This advances our understanding of how different cannabinoids produce analgesia through action at different voltage‐gated calcium channels and could influence the development of novel cannabinoid‐based therapeutics for treatment of chronic pain. [ABSTRACT FROM AUTHOR]

Objective(s): Gentamicin-induced nephrotoxicity was used as an experimental model of kidney disease. The present study was performed to assess the therapeutic role of cannabidiol (CBD) against gentamicin-induced renal damage. Materials and Methods: Forty two male Wistar rats were randomly allocated into 6 groups (n=7), including: (1) Control, (2) Vehicle, (3) Gentamicin-treated group (100 mg/kg/day) for 10 days (GM), (4-6) 3 Gentamicin-CBD-treated groups (2.5, 5, and 10 mg/kg/day) for 10 days (GM+CBD2.5, GM+CBD5, GM+CBD10). Serum levels of BUN and Cr, renal histology as well as real-time qRT-PCR were used to investigate the pattern of changes at different levels. Results: Gentamicin increased serum BUN and Cr (P<0.001), down-regulation of FXR (P<0.001), SOD (P<0.05) and up-regulation of CB1 receptor mRNA (P<0.01). Compared to the control group, CBD at 5 decreased (P<0.05) and at 10 mg/kg/day increased the expression of FXR (P<0.05). Nrf2 expression in CBD groups was increased (P<0.001 vs. GM). The expression of TNF-α compared to the control and GM groups, was significantly increased in CBD2.5 (P<0.01) and CBD10 (P<0.05). Compared to the control, CBD at 2.5 (P<0.01), 5 (P<0.001) and 10 (P<0.001) mg/kg/day significantly increased the expression of CB1R. Up-regulation of CB1R in the GM+CBD5, was significantly higher (P<0.05) than the GM group. Compared to the control group, the most significant increase in CB2 receptor expression was observed at CBD10 (P<0.05). Conclusion: CBD particularly at 10 mg/kg/day might be of significant therapeutic benefit against such renal complications. Activating the FXR/Nrf2 pathway and counteracting the deleterious effects of CB1 receptors via CB2 receptors scale-up could be part of the protective mechanisms of CBD. [ABSTRACT FROM AUTHOR]

Fatty acid-binding protein 7 (FABP7) aids in the intracellular transport of endogenous cannabinoids and is involved in regulating the stress response system. This study examined the role of FABP7 in chronic stress exposure through the binding of CB1 receptors. Adult male FABP7+/+ and FABP7-/- mice were treated with the unpredictable chronic mild stress (UCMS) procedure. After 28 days of treatment, mice were euthanized, and CB1 was measured with in vitro autoradiography using [3H] SR141716A. FABP7-/- mice, irrespective of stress treatment, showed reduced [3H] SR141716A binding in the amygdala, secondary somatosensory cortex, and ventral caudate putamen compared with the FABP7+/+ mice. Additionally, FABP7-/- mice treated with UCMS exhibited a reduction in CB1 binding in the globus pallidus and ventral caudate putamen compared with UCMS-treated FABP7+/+ mice. Genetic deletion of FABP7 can decrease CB1 expression in various brain regions; however, the underlying mechanism remains unclear. [ABSTRACT FROM AUTHOR]

ObjectiveThis study assessed the efficacy of INV-202, a novel peripherally restricted cannabinoid type-1 receptor (CB1R) inverse agonist, in a streptozotocin-induced type-1 diabetes nephropathy mouse model.MethodsDiabetes was induced in 8-week-old C57BL6/J male mice via intraperitoneal injection of streptozotocin (45 mg/kg/day for 5 days); nondiabetic controls received citrate buffer. Diabetic mice were randomized to 3 groups based on blood glucose, polyuria, and albuminuria, and administered daily oral doses for 28-days of INV-202 at 0.3 or 3 mg/kg or vehicle.ResultsINV-202 did not affect body weight but decreased kidney weight compared with the vehicle group. While polyuria was unaffected by INV-202 treatment, urinary urea (control 30.77 ± 14.93; vehicle 189.81 ± 31.49; INV-202 (0.3 mg/kg) 127.76 ± 20; INV-202 (3 mg/kg) 93.70 ± 24.97 mg/24h) and albumin (control 3.06 ± 0.38; vehicle 850.08 ± 170.50; INV-202 (0.3 mg/kg) 290.65 ± 88.70; INV-202 (3 mg/kg) 111.29 ± 33.47 µg/24h) excretion both decreased compared with vehicle-treated diabetic mice. Compared with the vehicle group, there was a significant improvement in the urinary albumin to creatinine ratio across INV-202 groups. Regardless of the dose, INV-202 significantly reduced angiotensin II excretion in diabetic mice. The treatment also decreased Agtr1a renal expression in a dose-dependent manner. Compared with nondiabetic controls, the glomerular filtration rate was increased in the vehicle group and significantly decreased by INV-202 at 3 mg/kg. While the vehicle group showed a significant loss in the mean number of podocytes per glomerulus, INV-202 treatment limited podocyte loss in a dose-dependent manner. Moreover, in both INV-202 groups, expression of genes coding for podocyte structural proteins nephrin (Nphs1), podocin (Nphs2), and podocalyxin (Pdxl) were restored to levels similar to nondiabetic controls. INV-202 partially limited the proximal tubular epithelial cell (PTEC) hyperplasia and normalized genetic markers for PTEC lesions. INV-202 also reduced expression of genes contributing to oxidative stress (Nox2, Nox4, and P47phox) and inflammation (Tnf). In addition, diabetes-induced renal fibrosis was significantly reduced by INV-202.ConclusionsINV-202 reduced glomerular injury, preserved podocyte structure and function, reduced injury to PTECs, and ultimately reduced renal fibrosis in a streptozotocin-induced diabetic nephropathy mouse model. These results suggest that INV-202 may represent a new therapeutic option in the treatment of diabetic kidney disease.

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. [Display omitted] • Dextromethorphan (DXM) produced anxiogenic-like behaviors. • Intra-MD microinjection of ACPA inhibited the anxiogenic effect of DXM. • The inhibition of MD CB1 receptors potentiated DXM response in the behavioral tasks. • Post-weaning TEX/EE treatment inhibited the DXM or AM251/DXM anxiogenic effects. [ABSTRACT FROM AUTHOR]

Chronic itch severely reduces the quality of life of patients. Electroacupuncture (EA) is widely used to treat chronic itch. However, the underlying mechanism of this therapeutic action of EA is largely unknown. Cannabinoid CB1 receptors in the ventrolateral periaqueductal gray (vlPAG) mediate the analgesic effect of EA. Using a dry skin-induced itch model in mice, we determined whether EA treatment reduces chronic itch via CB1 receptors in the vlPAG. We showed that the optimal inhibitory effect of EA on chronic itch was achieved at the high frequency and high intensity (100 Hz and 3 mA) at "Quchi" (LI11) and "Hegu" (LI14) acupoints, which are located in the same spinal dermatome as the cervical skin lesions. EA reversed the increased expression of CB1 receptors in the vlPAG and decreased the concentration of 5-hydroxytryptamine (5-HT) in the medulla oblongata and the expression of gastrin-releasing peptide receptors (GRPR) in the cervical spinal cord. Furthermore, knockout of CB1 receptors on GABAergic neurons in the vlPAG attenuated scratching behavior and the 5-HT concentration in the medulla oblongata. In contrast, knockout of CB1 receptors on glutamatergic neurons in the vlPAG blocked the antipruritic effects of EA and the inhibitory effect of EA on the 5-HT concentration in the medulla oblongata. Our findings suggest that EA treatment reduces chronic itch by activation of CB1 receptors on glutamatergic neurons and inhibition of CB1 receptors on GABAergic neurons in the vlPAG, thereby inhibiting the 5-HT release from the medulla oblongata to GRPR-expressing neurons in the spinal cord. Our findings suggest that EA attenuates chronic itch via activating CB1 receptors expressed on glutamatergic neurons and downregulating CB1 receptors on GABAergic neurons in the vlPAG, leading to the reduction in 5-HT release in the rostroventral medulla and GRPR signaling in the spinal cord. Our study not only advances our understanding of the mechanisms of the therapeutic effect of EA on chronic itch but also guides the selection of optimal parameters and acupoints of EA for treating chronic itch. [ABSTRACT FROM AUTHOR]

The therapeutic effects of electroacupuncture (EA) on the comorbidity of visceral pain and anxiety in patients with inflammatory bowel disease (IBD) is well known. It has been known that the ventral hippocampus (vHPC) and the cannabinoid type 1 receptors (CB1R) are involved in regulating anxiety and pain. Therefore, in this study, we determined whether EA reduces visceral pain and IBD-induced anxiety via CB1R in the vHPC. We found that EA alleviated visceral hyperalgesia and anxiety in TNBS-treated IBD mice. EA reversed overexpression of CB1R in IBD mice and decreased the percentage of CB1R-expressed GABAergic neurons in the vHPC. Ablating CB1R of GABAergic neurons in the vHPC alleviated anxiety in TNBS-treated mice and mimicked the anxiolytic effect of EA. While ablating CB1R in glutamatergic neurons in the vHPC induced severe anxiety in wild type mice and inhibited the anxiolytic effect of EA. However, ablating CB1R in either GABAergic or glutamatergic neurons in the vHPC did not alter visceral pain. In conclusion, we found CB1R in both GABAergic neurons and glutamatergic neurons are involved in the inhibitory effect of EA on anxiety but not visceral pain in IBD mice. EA may exert anxiolytic effect via downregulating CB1R in GABAergic neurons and activating CB1R in glutamatergic neurons in the vHPC, thus reducing the release of glutamate and inhibiting the anxiety circuit related to vHPC. Thus, our study provides new information about the cellular and molecular mechanisms of the therapeutic effect of EA on anxiety induced by IBD. [ABSTRACT FROM AUTHOR]

Synthetic cannabinoid receptor agonists (SCRAs) are a large group of abused psychoactive compounds that elicit numerous toxic effects not observed with cannabis , including death. Abuse of third-generation SCRA 5F-MDMB-PINACA (also known as 5F-ADB) has been associated with over 40 fatalities. This SCRA is metabolized to several active phase I metabolites, including excessively high post-mortem serum concentrations of an ester hydrolysis metabolite, 5F-MDMB-PINACA-M7 (M7). Although high serum concentrations of M7 (and other active metabolites) have been suggested to contribute to 5F-MDMB-PINACA toxicity, the affinity of M7 for CB1 receptors is unknown and more complete pharmacodynamic characterization of 5F-MDMB-PINACA and its active metabolites is needed. Competition binding and G-protein modulation studies presented here confirm reports that 5F-MDMB-PINACA and a second N -5-hydroxypentyl metabolite (M2) exhibit nM affinity and act as high efficacy agonists at CB1 receptors. Also as previously published, M7 exhibits high efficacy at CB1 receptors; however, demonstrated here for the first time, M7 retains only low μΜ affinity. Empirically derived K b values indicate rimonabant differentially antagonizes G-protein activation produced by 5F-MDMB-PINACA, relative to Δ9-THC (THC) or its metabolites. Chronic administration of 5F-MDMB-PINACA and metabolites results in CB1 down-regulation, but only 5F-MDMB-PINACA produces desensitization. Although low CB1 affinity/potency of M7 precluded in vivo studies, both M2 and THC produce locomotor suppression and CB1-mediated dose-dependent hypothermia and analgesia in mice. Collectively, these data confirm and extend previous studies suggesting that 5F-MDMB-PINACA is metabolized to active compounds exhibiting atypical pharmacodynamic properties at CB1 receptors, that may accumulate with parent drug to produce severe toxicity. [ABSTRACT FROM AUTHOR]

Alzheimer's disease (AD) is the most common type of dementia and neurodegeneration. The actual cause of AD progression is still unknown and no curative treatment is available. Recently, findings in human samples and animal models pointed to the endocannabinoid system (ECS) as a promising therapeutic approach against AD. However, the specific mechanisms by which cannabinoid drugs induce potential beneficial effects are still undefined. For this reason, it is required a full characterization of the ECS at different time points of AD progression considering important factors such as sex or the analysis of different brain regions to improve future cannabinoid-dependent therapies in AD. Thus, the main aim of the present study is to expand our knowledge of the status of the ECS in a presymptomatic period (3 months of age) using the AD mouse model APP/PS1 mice. First, we evaluated different behavioral domains including anxiety, cognitive functions, and social interactions in male and female APP/PS1 mice at 4 months of age. Although a mild working memory impairment was observed in male APP/PS1 mice, in most of the behaviors assessed we found no differences between genotypes. At 3 months of age, we performed a characterization of the ECS in different brain regions of the APP/PS1 mice considering the sex variable. We assessed the expression of the ECS components by quantitative Real-Time Polymerase Chain Reaction in the hippocampus, prefrontal cortex, hypothalamus, olfactory bulb, and cerebellum. Interestingly, gene expression levels of the type-1 and type-2 cannabinoid receptors and the anabolic and catabolic enzymes, differed depending on the brain region and the sex analyzed. For example, CB1R expression levels decreased in both hippocampus and prefrontal cortex of male APP/PS1 mice but increased in female mice. In contrast, CB2R expression was decreased in females, whereas males tended to have higher levels. Overall, our data indicated that the ECS is already altered in APP/PS1 mice at the presymptomatic stage, suggesting that it could be an early event contributing to the pathophysiology of AD or being a potential predictive biomarker. [ABSTRACT FROM AUTHOR]

Cannabinoid receptors, located throughout the body, are part of the endocannabinoid system. Cannabinoid CB1 and CB2 receptors are G protein-coupled receptors present from the early stages of gestation, which is involved in various physiological processes, including appetite, pain-sensation, mood, and memory. Due to the lipophilic nature of cannabinoids, it was initially thought that these compounds exert several biological effects by disrupting the cell membrane nonspecifically. Recent biochemical and behavioral findings have demonstrated that blockade of CB1 receptors engenders antidepressant-like neurochemical changes (increases in extracellular levels of monoamines in cortical but not subcortical brain regions) and behavioral effects consistent with antidepressant/antistress activity. We aim to define various roles of cannabinoid receptors in modulating signaling pathways and association with several pathophysiological conditions.

Alzheimer’s disease (AD) is the most common type of dementia and neurodegeneration. The actual cause of AD progression is still unknown and no curative treatment is available. Recently, findings in human samples and animal models pointed to the endocannabinoid system (ECS) as a promising therapeutic approach against AD. However, the specific mechanisms by which cannabinoid drugs induce potential beneficial effects are still undefined. For this reason, it is required a full characterization of the ECS at different time points of AD progression considering important factors such as sex or the analysis of different brain regions to improve future cannabinoid-dependent therapies in AD. Thus, the main aim of the present study is to expand our knowledge of the status of the ECS in a presymptomatic period (3 months of age) using the AD mouse model APP/PS1 mice. First, we evaluated different behavioral domains including anxiety, cognitive functions, and social interactions in male and female APP/PS1 mice at 4 months of age. Although a mild working memory impairment was observed in male APP/PS1 mice, in most of the behaviors assessed we found no differences between genotypes. At 3 months of age, we performed a characterization of the ECS in different brain regions of the APP/PS1 mice considering the sex variable. We assessed the expression of the ECS components by quantitative Real-Time Polymerase Chain Reaction in the hippocampus, prefrontal cortex, hypothalamus, olfactory bulb, and cerebellum. Interestingly, gene expression levels of the type-1 and type-2 cannabinoid receptors and the anabolic and catabolic enzymes, differed depending on the brain region and the sex analyzed. For example, CB1R expression levels decreased in both hippocampus and prefrontal cortex of male APP/PS1 mice but increased in female mice. In contrast, CB2R expression was decreased in females, whereas males tended to have higher levels. Overall, our data indicated that the ECS is already altered in APP/PS1 mice at the presymptomatic stage, suggesting that it could be an early event contributing to the pathophysiology of AD or being a potential predictive biomarker.

2-Arachidonoylglycerol (2-AG) is the most prevalent endocannabinoid involved in maintaining brain homeostasis. Previous studies have demonstrated that inactivating monoacylglycerol lipase (MAGL), the primary enzyme responsible for degrading 2-AG in the brain, alleviates neuropathology and prevents synaptic and cognitive decline in animal models of neurodegenerative diseases. However, we show that selectively inhibiting 2-AG metabolism in neurons impairs cognitive function in mice. This cognitive impairment appears to result from decreased expression of synaptic proteins and synapse numbers, impaired long-term synaptic plasticity and cortical circuit functional connectivity, and diminished neurogenesis. Interestingly, the synaptic and cognitive deficits induced by neuronal MAGL inactivation can be counterbalanced by inhibiting astrocytic 2-AG metabolism. Transcriptomic analyses reveal that inhibiting neuronal 2-AG degradation leads to widespread changes in expression of genes associated with synaptic function. These findings suggest that crosstalk in 2-AG signaling between astrocytes and neurons is crucial for maintaining synaptic and cognitive functions and that excessive 2-AG in neurons alone is detrimental to cognitive function.

Parkinson’s disease (PD) is a neurodegenerative disease usually caused by neuroinflammation, oxidative stress and other etiologies. Recent studies have found that the cannabinoid system present in the basal ganglia has a strong influence on the progression of PD. Altering the cannabinoid receptor activation status by modulating endogenous cannabinoid (eCB) levels can exert an anti-movement disorder effect. Therefore, the development of drugs that modulate the endocannabinoid system may be a novel strategy for the treatment of PD. However, eCB regulation is complex, with diverse cannabinoid receptor functions and the presence of dopaminergic, glutamatergic, and γ-aminobutyric signals interacting with cannabinoid signaling in the basal ganglia region. Therefore, the study of eCB is challenging. Here, we have described the function of the cannabinoid system in the basal ganglia and its association with PD in three parts (eCBs, cannabinoid receptors, and factors regulating the cannabinoid metabolism) and summarized the mechanisms of action related to the cannabinoid analogs currently aimed at treating PD. The shortcomings identified from previous studies and the directions that should be explored in the future will provide insights into new approaches and ideas for the future development of cannabinoid-based drugs and the treatment of PD.

Parkinson's disease (PD) is a neurodegenerative disease usually caused by neuroinflammation, oxidative stress and other etiologies. Recent studies have found that the cannabinoid system present in the basal ganglia has a strong influence on the progression of PD. Altering the cannabinoid receptor activation status by modulating endogenous cannabinoid (eCB) levels can exert an anti-movement disorder effect. Therefore, the development of drugs that modulate the endocannabinoid system may be a novel strategy for the treatment of PD. However, eCB regulation is complex, with diverse cannabinoid receptor functions and the presence of dopaminergic, glutamatergic, and γ-aminobutyric signals interacting with cannabinoid signaling in the basal ganglia region. Therefore, the study of eCB is challenging. Here, we have described the function of the cannabinoid system in the basal ganglia and its association with PD in three parts (eCBs, cannabinoid receptors, and factors regulating the cannabinoid metabolism) and summarized the mechanisms of action related to the cannabinoid analogs currently aimed at treating PD. The shortcomings identified from previous studies and the directions that should be explored in the future will provide insights into new approaches and ideas for the future development of cannabinoid-based drugs and the treatment of PD. [ABSTRACT FROM AUTHOR]

Emerging data indicate that endocannabinoid signaling is critical to the formation of habitual behavior. Previous work demonstrated that antagonism of cannabinoid receptor type 1 (CB1R) with AM251 during operant training impairs habit formation, but it is not known if this behavioral effect is specific to disrupted signaling of the endocannabinoid ligands anandamide or 2‐arachidonoyl glycerol (2‐AG). Here, we used selective pharmacological compounds during operant training to determine the impact of fatty acid amide hydrolase (FAAH) inhibition to increase anandamide (and other n‐acylethanolamines) or monoacylglycerol lipase (MAGL) inhibition to increase 2‐AG levels on the formation of habitual behaviors in mice using a food‐reinforced contingency degradation procedure. We found, contrary to our hypothesis, that inhibition of FAAH and of MAGL disrupted the formation of habits. Next, AM251 was administered during training to verify that impaired habit formation could be assessed using contingency degradation. AM251‐exposed mice responded at lower rates during training and at higher rates in the test. To understand the inconsistency with published data, we performed a proof‐of‐principle dose–response experiment to compare AM251 in our vehicle‐solution to the published vehicle‐suspension on response rates. We found consistent reductions in response rate with increasing doses of AM251 in solution and an inconsistent dose–response relationship with AM251 in suspension. Together, our data suggest that further characterization of the role of CB1R signaling in the formation of habitual responding is warranted and that augmenting endocannabinoids may have clinical utility for prophylactically preventing aberrant habit formation such as that hypothesized to occur in substance use disorders. [ABSTRACT FROM AUTHOR]

Several studies support the notion that exploratory behaviour depends on the functionality of the cannabinoid type 1 (CB1) receptor in a cell type‐specific manner. Mice lacking the CB1 receptor in forebrain GABAergic or dorsal telencephalic glutamatergic neurons have served as essential tools revealing the necessary CB1 receptor functions in these two neuronal populations. However, whether these specific CB1 receptor populations are also sufficient within the endocannabinoid system for wild‐type‐like exploratory behaviour has remained unknown. To evaluate cell‐type‐specific sufficiency of CB1 receptor signalling exclusively in dorsal telencephalic glutamatergic neurons (Glu‐CB1‐RS) or in forebrain GABAergic neurons (GABA‐CB1‐RS), we utilised a mouse model in which CB1 receptor expression can be reactivated conditionally at endogenous levels from a complete CB1‐KO background. The two types of conditional CB1‐rescue mice were compared with CB1 receptor‐deficient [no reactivation (Stop‐CB1)] and wild‐type [ubiquitous reactivation of endogenous CB1 receptor (CB1‐RS)] controls to investigate the behavioural consequences. We evaluated social and object exploratory behaviour in four different paradigms. Remarkably, the reduced exploration observed in Stop‐CB1 animals was rescued in Glu‐CB1‐RS mice and sometimes even surpassed CB1‐RS (wild‐type) exploration. In contrast, GABA‐CB1‐RS animals showed the lowest exploratory drive in all paradigms, with an even stronger phenotype than Stop‐CB1 mice. Interestingly, these effects weakened with increasing familiarity with the environment, suggesting a causal role for altered neophobia in the observed phenotypes. Taken together, using our genetic approach, we were able to substantiate the opposing role of the CB1 receptor in dorsal telencephalic glutamatergic versus forebrain GABAergic neurons regarding exploratory behaviour. [ABSTRACT FROM AUTHOR]

• Endocannabinoid system induces dual effects in epilepsy. • Endocannabinoids can induce neuroinflammation and neurotoxicity. • The effects of endocannabinoids can depend on the pathological microenvironment. Epilepsy is a neurological disorder with a high prevalence worldwide. Several studies carried out during the last decades indicate that the administration of cannabinoids as well as the activation of the endocannabinoid system (ECS) represent a therapeutic strategy to control epilepsy. However, there are controversial studies indicating that activation of ECS results in cell damage, inflammation and neurotoxicity, conditions that facilitate the seizure activity. The present review is focused to present findings supporting this issue. According to the current discrepancies, it is relevant to elucidate the different effects induced by the activation of ECS and determine the conditions under which it facilitates the seizure activity. [ABSTRACT FROM AUTHOR]

Depression is a common mental disorder and is the leading cause of suicide globally. Because of the significant diversity in mental disorders, accurate diagnosis is difficult. Hence, the investigation of novel biomarkers is a key research perspective in psychotherapy to enable an individually tailored treatment approach. The prefrontal cortex (PFC) is a vital cortical region whose circuitry has been implicated in the development of depressive disorder. The endocannabinoid system (ECS) has garnered increasing attention because of its involvement in several diverse physiological brain processes including regulation of emotional, motivational and cognitive functions. The current review article explores the function of the key elements of the ECS as a biomarker in depressive disorder. The activity of endocannabinoids is thought to be moderated by the CB1 receptors in the central nervous system (CNS). Variations in the concentration of endocannabinoids and the binding affinity of CB1 receptors and their density have been identified in the PFC of persons with depression. Such discoveries support our theory that alteration in endocannabinoid function leads to the pathophysiological features of depressive disorders. Moreover, evidence from animal and human studies has revealed that dysfunction in endocannabinoid signalling can produce depression-like behaviours; therefore, improvement of endocannabinoid signalling may represent a new therapeutic approach for the management of depressive disorders. [ABSTRACT FROM AUTHOR]

Pharmacological studies allow to suggest that activation of cannabinoid type 1 receptors (CB1) have a neuroprotective role against toxicity induced by organophosphate agents, but the exact mechanisms of this effect as well as interaction with receptors of other types are far from clear. Therefore, the aim of current study was to evaluate the effect of CB1 and NMDA receptors agonists on cell viability and biomarkers of oxidative stress and lipid peroxidation in PC12 cells exposed to paraoxon. PC12 cells were exposed to 100 µm paraoxon as organophosphate agent. Treatments with 1 µM arachidonyl-2′-chloroethylamide (ACEA) as specific agonist of CB1 receptors, 100 µM N-methyl-D-aspartate (NMDA) as agonist of NMDA receptors and 1 µM AM251 as antagonist of CB1 receptors were done. Cell via­bility and biomarkers of oxidative stress were evaluated after 48 h of incubation. The level of CB1 receptor protein was evaluated by Western blotting. It was demonstrated that PC12 cells treatment with paraoxon led to cell viability inhibition, glutathione level, superoxide dismutase and catalase activity reduction, lipid peroxidation intensification and CB1 receptor expression attenuation. Application of ACEA and NMDA was shown to be followed by normalization of these indices. The protective effect of ACEA was abolished when the CB1 receptors antagonist AM251 was applied. The study revealed that application of ACEA and NMDA can protect PC12 cells against paraoxon induced toxicity through antioxidant capacity increment, lipid peroxidation inhibition and enhanced expression of CB1 receptors.

Endocannabinoids modulate mesolimbic (MSL) dopamine (DA) neurons firing at the ventral tegmental area (VTA). These neurons are activated by copulation, increasing DA release in nucleus accumbens (NAcc). Copulation to satiety in male rats implies repeated ejaculation within a short period (around 2.5 h), during which NAcc dopamine concentrations remain elevated, suggesting continuous neuronal activation. During the 72 h that follow copulation to satiety, males exhibit long-lasting changes suggestive of brain plasticity processes. Enhanced DA neuron activity triggers the synthesis and release of endocannabinoids (eCBs) in the VTA, which participate in several long-term synaptic plasticity processes. Blockade of cannabinoid type 1 receptors (CB1Rs) during copulation to satiety interferes with the appearance of the plastic changes. Glutamatergic inputs to the VTA express CB1Rs and contribute to DA neuron burst firing and synaptic plasticity. We hypothesized that eCBs, released during copulation to satiety, would activate VTA CB1Rs and modulate synaptic plasticity processes involving glutamatergic transmission. To test this hypothesis, we determined changes in VTA CB1R density, phosphorylation, and internalization in rats that copulated to satiety 24 h earlier as compared both to animals that ejaculated only once and to sexually experienced unmated males. Changes in glutamate AMPAR and NMDAR densities and subunit composition and in ERK1/2 activation were determined in the VTA of males that copulated to satiety in the presence or absence of AM251, a CB1R antagonist. The CB1R density decreased and the proportion of phosphorylated CB1Rs increased in the animals that copulated compared to control rats. The CB1R internalization was detected only in sexually satiated males. A decrease in α-amino-3-hydroxy-5-methylisoxazole-4-propionate receptor (AMPAR) density, blocked by AM251 pretreatment, and an increase in the proportion of GluA2-AMPARs occurred in sexually satiated rats. GluN2A- N-methyl-D-aspartate receptor (NMDAR) expression decreased, and GluN2B-NMDARs increased in these animals, both of which were prevented by AM251 pre-treatment. An increase in phosphorylated ERK1/2 emerged in males copulating to satiety in the presence of AM251. Results demonstrate that during copulation to satiety, eCBs activate CB1Rs in the VTA, producing changes in glutamate receptors compatible with a reduced neuronal activation. These changes could play a role in the induction of the long-lasting physiological changes that characterize sexually satiated rats.

Objective: The aim of this study was to test the hypothesis that synthesis of nitric oxide (NO) and activation of CB1 receptors have opposite effects in a behavioural animal model of panic and anxiety. Methods: To test the hypothesis, male Wistar rats were exposed to the elevated T-maze (ETM) model under the following treatments: L-Arginine (L-Arg) was administered before treatment with WIN55,212-2, a CB1 receptor agonist; AM251, a CB1 antagonist, was administered before treatment with L-Arg. All treatments were by intraperitoneal route. Results: The CB1 receptor agonist, WIN55,212-2 (1 mg/kg), induced an anxiolytic-like effect, which was prevented by pretreatment with an ineffective dose of L-Arg (1 mg/kg). Administration of AM251 (1 mg/kg), a CB1 antagonist before treatment with L-Arg (1 mg/kg) did not produce anxiogenic-like responses. Conclusion: Altogether, this study suggests that the anxiolytic-like effect of cannabinoids may occur through modulation of NO signalling. [ABSTRACT FROM AUTHOR]

The endocannabinoid system (ECS) critically regulates stress responsivity and emotional behavior throughout development. It regulates anxiety‐like behaviors in humans and animal models. In addition, it is sensitive to early life stress at the gene expression level in a sex‐dependent and region‐dependent manner, and these changes are already evident in the adolescent brain. The ECS modulates the neuroendocrine and behavioral effects of stress, and is also capable of being affected by stress exposure itself. Early life stress interferes with the development of corticolimbic circuits, a major location of endocannabinoid receptors, and increases vulnerability to adult psychopathology. Early life stress alters the ontogeny of the ECS, resulting in a sustained deficit in its function, particularly within the hippocampus. Specifically, exposure to early stress results in bidirectional changes in anandamide and 2‐AG tissue levels within the amygdala and hippocampus and reduces hippocampal endocannabinoid function at puberty. CB1 receptor densities across all brain regions are downregulated later in life following exposure to early life stress. Manipulations affecting the glucocorticoid and the endocannabinoid systems persistently adjust individual emotional responses and synaptic plasticity. This review aims to show the bidirectional trajectories of endocannabinoid modulation of emotionality in reaction to early life stress. [ABSTRACT FROM AUTHOR]

Cannabinoids and Cannabis-derived compounds have been receiving especial attention in the epilepsy research scenario. Pharmacological modulation of endocannabinoid system's components, like cannabinoid type 1 receptors (CB1R) and their bindings, are associated with seizures in preclinical models. CB1R expression and functionality were altered in humans and preclinical models of seizures. Additionally, Cannabis-derived compounds, like cannabidiol (CBD), present anticonvulsant activity in humans and in a great variety of animal models. Audiogenic seizures (AS) are induced in genetically susceptible animals by high-intensity sound stimulation. Audiogenic strains, like the Genetically Epilepsy Prone Rats, Wistar Audiogenic Rats, and Krushinsky-Molodkina, are useful tools to study epilepsy. In audiogenic susceptible animals, acute acoustic stimulation induces brainstem-dependent wild running and tonic-clonic seizures. However, during the chronic protocol of AS, the audiogenic kindling (AuK), limbic and cortical structures are recruited, and the initially brainstem-dependent seizures give rise to limbic seizures. The present study reviewed the effects of pharmacological modulation of the endocannabinoid system in audiogenic seizure susceptibility and expression. The effects of Cannabis-derived compounds in audiogenic seizures were also reviewed, with especial attention to CBD. CB1R activation, as well Cannabis-derived compounds, induced anticonvulsant effects against audiogenic seizures, but the effects of cannabinoids modulation and Cannabis-derived compounds still need to be verified in chronic audiogenic seizures. The effects of cannabinoids and Cannabis-derived compounds should be further investigated not only in audiogenic seizures, but also in epilepsy related comorbidities present in audiogenic strains, like anxiety, and depression.

Cannabinoid receptors 1 and 2 (CB1 and CB2, respectively) play an important role in maintaining the integrity of the blood–brain barrier (BBB). On the other hand, BBB dysfunction is a common feature in drug-resistant epilepsy. The focus of the present study was to characterize protein expression levels and Gαi/o protein-induced activation by CB1 and CB2 receptors in the microvascular endothelial cells (MECs) isolated from the brain of patients with drug-resistant mesial temporal lobe epilepsy (DR-MTLE). MECs were isolated from the hippocampus and temporal neocortex of 12 patients with DR-MTLE and 12 non-epileptic autopsies. Immunofluorescence experiments were carried out to determine the localization of CB1 and CB2 receptors in the different cell elements of MECs. Protein expression levels of CB1 and CB2 receptors were determined by Western blot experiments. [35S]-GTPγS binding assay was used to evaluate the Gαi/o protein activation induced by specific agonists. Immunofluorescent double-labeling showed that CB1 and CB2 receptors colocalize with tight junction proteins (claudin-5, occludin, and zonula occludens-1), glial fibrillary acidic protein and platelet-derived growth factor receptor-β. These results support that CB1 and CB2 receptors are expressed in the human isolated microvessels fragments consisting of MECs, astrocyte end feet, and pericytes. The hippocampal microvasculature of patients with DR-MTLE presented lower protein expression of CB1 and CB2 receptors (66 and 43%, respectively; p < 0.001). However, its Gαi/o protein activation was with high efficiency (CB1, 251%, p < 0.0008; CB2, 255%, p < 0.0001). Microvasculature of temporal neocortex presented protein overexpression of CB1 and CB2 receptors (35 and 41%, respectively; p < 0.01). Their coupled Gαi/o protein activation was with higher efficiency for CB1 receptors (103%, p < 0.006), but lower potency (p < 0.004) for CB2 receptors. The present study revealed opposite changes in the protein expression of CB1 and CB2 receptors when hippocampus (diminished expression of CB1 and CB2) and temporal neocortex (increased expression of CB1 and CB2) were compared. However, the exposure to specific CB1 and CB2 agonists results in high efficiency for activation of coupled Gαi/o proteins in the brain microvasculature of patients with DR-MTLE. CB1 and CB2 receptors with high efficiency could represent a therapeutic target to maintain the integrity of the BBB in patients with DR-MTLE.

Anxiety disorder is a well-recognized condition observed in subjects submitted to acute stress. Although the brain mechanisms underlying this disorder remain unclear, the available evidence indicates that oxidative stress and GABAergic dysfunction mediate the generation of stress-induced anxiety. Cannabinoids are known to be efficient modulators of behavior, given that the activation of the cannabinoid receptors type-1 (CB1 receptors) induces anxiolytic-like effects in animal models. In the present study, we aimed to describe the effects of the stimulation of the CB1 receptors on anxiety-like behavior, oxidative stress, and the GABA content of the brains of zebrafish submitted to acute restraint stress (ARS). The animals submitted to the ARS protocol presented evident anxiety-like behavior with increased lipid peroxidation in the brain tissue. The evaluation of the levels of GABA in the zebrafish telencephalon presented decreased levels of GABA in the ARS group in comparison with the control. Treatment with ACEA, a specific CB1 receptor agonist, prevented ARS-induced anxiety-like behavior and oxidative stress in the zebrafish brain. ACEA treatment also prevented a decrease in GABA in the telencephalon of the animals submitted to the ARS protocol. Overall, these preclinical data strongly suggest that the CB1 receptors represent a potential target for the development of the treatment of anxiety disorders elicited by acute stress.

The antioxidant and CB2 receptor agonist properties of Δ9-tetrahydrocannabivarin (Δ9-THCV) afforded neuroprotection in experimental Parkinson's disease (PD), whereas its CB1 receptor antagonist profile at doses lower than 5 mg/kg caused anti-hypokinetic effects. In the present study, we investigated the anti-dyskinetic potential of Δ9-THCV (administered i.p. at 2 mg/kg for two weeks), which had not been investigated before. This objective was investigated after inducing dyskinesia by repeated administration of L-DOPA (i.p. at 10 mg/kg) in a genetic model of dopaminergic deficiency, Pitx3ak mutant mice, which serves as a useful model for testing anti-dyskinetic agents. The daily treatment of these mice with L-DOPA for two weeks progressively increased the time spent in abnormal involuntary movements (AIMs) and elevated their horizontal and vertical activities (as measured in a computer-aided actimeter), signs that reflected the dyskinetic state of these mice. Interestingly, when combined with L-DOPA from the first injection, Δ9-THCV delayed the appearance of all these signs and decreased their intensity, with a reduction in the levels of FosB protein and the histone pAcH3 (measured by immunohistochemistry), which had previously been found to be elevated in the basal ganglia in L-DOPA-induced dyskinesia. In addition to the anti-dyskinetic effects of Δ9-THCV when administered at the onset of L-DOPA treatment, Δ9-THCV was also effective in attenuating the intensity of dyskinesia when administered for three consecutive days once these signs were already present (two weeks after the onset of L-DOPA treatment). In summary, our data support the anti-dyskinetic potential of Δ9-THCV, both to delay the occurrence and to attenuate the magnitude of dyskinetic signs. Although further studies are clearly required to determine the clinical significance of these data in humans, the results nevertheless situate Δ9-THCV in a promising position for developing a cannabinoid-based therapy for patients with PD.

Introduction: Non-Alcoholic Fatty Liver Disease (NAFLD) is hepatic manifestation of metabolic syndrome. It represents a spectrum of diseases ranging from steatosis, non-alcoholic steatohepatitis (NASH), that may progress to fibrosis, cirrhosis and eventually hepatocellular carcinoma. Aim: the aim of the study was to investigate the influence of CB 1 cannabinoid receptor blockade on the intensity of oxidative/nitrosative stress in mice liver with NAFLD. Therefore, we used rimonabant, selective CB 1 antagonist. Material and Methods: Male mice C57BL/6 (n = 28) were divided into following groups: 1) Control group-fed with control chow diet 20 weeks (C group; n = 7), 2) Group fed with high saturated fat diet 20 weeks (HF group; n = 7), 3) Group fed with standard chow diet and treated with rimonabant after 18 weeks (R group; n = 7), 4) Group fed with high saturated fat diet and treated with rimonabant after 18 weeks (HFR group; n = 7). The activity of liver tran-saminases was measured in serum. The concentrations of malondialdehyde (MDA), nitrites and nitrates (NO x), and the activity of superoxide dismutase (SOD), copper/zinc superoxide dismutase (Cu/ZnSOD) and manganese superoxide dismutase (MnSOD) were measured in the liver. Results: Rimonabant induced decrease in transaminase activity in R group compared to control , as well as in HFR group compared to HF group (p < 0.01, respectively). Concentrations of MDA and NO x were lower in HFR compared to HF group (p < 0.01). We found decrease in SOD, Cu/ZnSOD and MnSOD activities in HFR group compared to HF group (p < 0.01). Conclusion: According to the results of this study, it can be concluded that blockade of CB 1 receptors causes useful effects in the treatment of NAFLD. Rimonabant reduced hepatocellu-lar injury, which was proved by decreased transaminase activities. The reduction of oxidative/ nitrosative stress and lipid peroxidation may also contribute to the protective effects of rimonabant, which has been shown as decrease in MDA and NOx concentration.

Keywords: cannabinoids; CB1 receptors; CB2 receptors; Parkinson's disease (PD); basal ganglia; RCT - randomized controlled trial; commentary articles EN cannabinoids CB1 receptors CB2 receptors Parkinson's disease (PD) basal ganglia RCT - randomized controlled trial commentary articles 1 3 3 05/12/22 20220509 NES 220509 Introduction This is a review article on the biological role of the cannabinoid system in the pathophysiology of Parkinson's disease (PD). CB1 receptors, Parkinson's disease (PD), cannabinoids, CB2 receptors, basal ganglia, RCT - randomized controlled trial, commentary articles Regarding the effects of CB1 on neurotransmission, enhanced CB1 receptor transmission in the striatum and in the output ganglia of globus pallidus (GP) internus/substantia nigra pars reticulata may alleviate PD symptoms, whereas if CB1 is activated in GP externus, it exacerbates PD symptoms (Wang et al., [6]). [Extracted from the article]

Background and Purpose: Women are twice as likely as men to develop post‐traumatic stress disorder (PTSD) making the search for biological mechanisms underlying these gender disparities especially crucial. One of the hallmark symptoms of PTSD is an alteration in the ability to extinguish fear responses to trauma‐associated cues. In male rodents, the endocannabinoid system can modulate fear extinction and has been suggested as a therapeutic target for PTSD. However, whether and how the endocannabinoid system may modulate fear expression and extinction in females remains unknown. Experimental Approach To answer this question, we pharmacologically manipulated endocannabinoid signalling in male and female rats prior to extinction of auditory conditioned fear and measured both passive (freezing) and active (darting) conditioned responses. Key Results: Surprisingly, we found that acute systemic inhibition of the endocannabinoid anandamide (AEA) or 2‐arachidonoyl glycerol (2‐AG) hydrolysis did not significantly alter fear expression or extinction in males. However, the same manipulations in females produced diverging effects. Increased AEA signalling at vanilloid TRPV1 receptors impaired fear memory extinction. In contrast, inhibition of 2‐AG hydrolysis promoted active over passive fear responses acutely via activation of cannabinoid1 (CB1) receptors. Measurement of AEA and 2‐AG levels after extinction training revealed sex‐ and brain region‐specific changes. Conclusion and Implications: We provide the first evidence that AEA and 2‐AG signalling affect fear expression and extinction in females in opposite directions. These findings are relevant to future research on sex differences in mechanisms of fear extinction and may help develop sex‐specific therapeutics to treat trauma‐related disorders. [ABSTRACT FROM AUTHOR]

Cannabinoids and Cannabis -derived compounds have been receiving especial attention in the epilepsy research scenario. Pharmacological modulation of endocannabinoid system's components, like cannabinoid type 1 receptors (CB1R) and their bindings, are associated with seizures in preclinical models. CB1R expression and functionality were altered in humans and preclinical models of seizures. Additionally, Cannabis -derived compounds, like cannabidiol (CBD), present anticonvulsant activity in humans and in a great variety of animal models. Audiogenic seizures (AS) are induced in genetically susceptible animals by high-intensity sound stimulation. Audiogenic strains, like the Genetically Epilepsy Prone Rats, Wistar Audiogenic Rats, and Krushinsky-Molodkina, are useful tools to study epilepsy. In audiogenic susceptible animals, acute acoustic stimulation induces brainstem-dependent wild running and tonic-clonic seizures. However, during the chronic protocol of AS, the audiogenic kindling (AuK), limbic and cortical structures are recruited, and the initially brainstem-dependent seizures give rise to limbic seizures. The present study reviewed the effects of pharmacological modulation of the endocannabinoid system in audiogenic seizure susceptibility and expression. The effects of Cannabis -derived compounds in audiogenic seizures were also reviewed, with especial attention to CBD. CB1R activation, as well Cannabis -derived compounds, induced anticonvulsant effects against audiogenic seizures, but the effects of cannabinoids modulation and Cannabis -derived compounds still need to be verified in chronic audiogenic seizures. The effects of cannabinoids and Cannabis -derived compounds should be further investigated not only in audiogenic seizures, but also in epilepsy related comorbidities present in audiogenic strains, like anxiety, and depression. [ABSTRACT FROM AUTHOR]

Cannabinoid receptors 1 and 2 (CB1 and CB2, respectively) play an important role in maintaining the integrity of the blood–brain barrier (BBB). On the other hand, BBB dysfunction is a common feature in drug-resistant epilepsy. The focus of the present study was to characterize protein expression levels and Gαi/o protein-induced activation by CB1 and CB2 receptors in the microvascular endothelial cells (MECs) isolated from the brain of patients with drug-resistant mesial temporal lobe epilepsy (DR-MTLE). MECs were isolated from the hippocampus and temporal neocortex of 12 patients with DR-MTLE and 12 non-epileptic autopsies. Immunofluorescence experiments were carried out to determine the localization of CB1 and CB2 receptors in the different cell elements of MECs. Protein expression levels of CB1 and CB2 receptors were determined by Western blot experiments. [35S]-GTPγS binding assay was used to evaluate the Gαi/o protein activation induced by specific agonists. Immunofluorescent double-labeling showed that CB1 and CB2 receptors colocalize with tight junction proteins (claudin-5, occludin, and zonula occludens-1), glial fibrillary acidic protein and platelet-derived growth factor receptor-β. These results support that CB1 and CB2 receptors are expressed in the human isolated microvessels fragments consisting of MECs, astrocyte end feet, and pericytes. The hippocampal microvasculature of patients with DR-MTLE presented lower protein expression of CB1 and CB2 receptors (66 and 43%, respectively; p < 0.001). However, its Gαi/o protein activation was with high efficiency (CB1, 251%, p < 0.0008; CB2, 255%, p < 0.0001). Microvasculature of temporal neocortex presented protein overexpression of CB1 and CB2 receptors (35 and 41%, respectively; p < 0.01). Their coupled Gαi/o protein activation was with higher efficiency for CB1 receptors (103%, p < 0.006), but lower potency (p < 0.004) for CB2 receptors. The present study revealed opposite changes in the protein expression of CB1 and CB2 receptors when hippocampus (diminished expression of CB1 and CB2) and temporal neocortex (increased expression of CB1 and CB2) were compared. However, the exposure to specific CB1 and CB2 agonists results in high efficiency for activation of coupled Gαi/o proteins in the brain microvasculature of patients with DR-MTLE. CB1 and CB2 receptors with high efficiency could represent a therapeutic target to maintain the integrity of the BBB in patients with DR-MTLE. [ABSTRACT FROM AUTHOR]

Anxiety disorder is a well-recognized condition observed in subjects submitted to acute stress. Although the brain mechanisms underlying this disorder remain unclear, the available evidence indicates that oxidative stress and GABAergic dysfunction mediate the generation of stress-induced anxiety. Cannabinoids are known to be efficient modulators of behavior, given that the activation of the cannabinoid receptors type-1 (CB1 receptors) induces anxiolytic-like effects in animal models. In the present study, we aimed to describe the effects of the stimulation of the CB1 receptors on anxiety-like behavior, oxidative stress, and the GABA content of the brains of zebrafish submitted to acute restraint stress (ARS). The animals submitted to the ARS protocol presented evident anxiety-like behavior with increased lipid peroxidation in the brain tissue. The evaluation of the levels of GABA in the zebrafish telencephalon presented decreased levels of GABA in the ARS group in comparison with the control. Treatment with ACEA, a specific CB1 receptor agonist, prevented ARS-induced anxiety-like behavior and oxidative stress in the zebrafish brain. ACEA treatment also prevented a decrease in GABA in the telencephalon of the animals submitted to the ARS protocol. Overall, these preclinical data strongly suggest that the CB1 receptors represent a potential target for the development of the treatment of anxiety disorders elicited by acute stress. [ABSTRACT FROM AUTHOR]

Drugs of abuse, including cocaine, alter the mechanisms underpinning synaptic plasticity, including long‐term potentiation of glutamatergic synapses in the mesolimbic system. These effects are thought to underlie addictive behaviors. In the ventral tegmental area (VTA), glutamatergic synapses also exhibit long‐term depression (LTD), a type of plasticity that weakens synaptic strength. This form of synaptic plasticity is induced by low‐frequency stimulation and mediated by endocannabinoid (eCB) signaling, which also modulates addictive behaviors. However, it remains unknown whether eCB‐LTD in the VTA could be altered by cocaine use. Therefore, the goal of the present study was to examine the impact of cocaine self‐administration on eCB‐LTD of glutamatergic synapses onto VTA dopaminergic (DA) neurons. To that end, male rats underwent cocaine (0.75 mg/kg/infusion) or saline self‐administration under the fixed ratio 1 schedule for 6–9 days. One day after the last self‐administration session, the magnitude of eCB‐LTD was examined using ex vivo whole‐cell recordings of putative VTA DA neurons from naïve rats and rats with saline or cocaine self‐administration. The results revealed that cocaine self‐administration abolished eCB‐LTD. The cocaine‐induced blockade of eCB‐LTD in the VTA was mediated by an impaired function of presynaptic CB1 receptors. Collectively, these findings indicate that cocaine exposure blunts eCB‐mediated synaptic plasticity in midbrain DA neurons. This effect could be one of the cellular mechanisms that mediate, at least in part, addictive behaviors. [ABSTRACT FROM AUTHOR]

• Exogenous cannabinoid agonist decreases inhibitory inputs from all aPC layers. • DSI is present in the three layers of aPC inhibitory synapses. • iLTD and CCK interneurons are restricted to inhibitory synapses located in layer II and III of the aPC. • CCK interneurons might be necessary for iLTD but not for DSI. In the olfactory system, the endocannabinoid system (ECS) regulates sensory perception and memory. A major structure involved in these processes is the anterior piriform cortex (aPC), but the impact of ECS signaling in aPC circuitry is still scantly characterized. Using ex vivo patch clamp experiments in mice and neuroanatomical approaches, we show that the two major forms of ECS-dependent synaptic plasticity, namely depolarization-dependent suppression of inhibition (DSI) and long-term depression of inhibitory transmission (iLTD) are present in the aPC. Interestingly, iLTD expression depends on layer localization of the inhibitory neurons associated with the expression of the neuropeptide cholecystokinin. Conversely, the decrease of inhibitory transmission induced by exogenous cannabinoid agonists or DSI do not seem to be impacted by these factors. Altogether, these results indicate that CB1 receptors exert an anatomically specific and differential control of inhibitory plasticity in the aPC, likely involved in spatiotemporal regulation of olfactory processes. [ABSTRACT FROM AUTHOR]

Alterations in the expanded endocannabinoid system (eECS) and cell membrane composition have been implicated in the pathophysiology of schizophrenia spectrum disorders. We enrolled 54 antipsychotic (AP)-naïve first-episode psychosis (FEP) patients and 58 controls and applied a targeted metabolomics approach followed by multivariate data analysis to investigate the profile changes in the serum levels of endocannabinoids: 2-arachidonoylglycerol (2-AG) and anandamide, endocannabinoids-like N-acylethanolamines (NAEs: linoleoylethanolamide, oleoylethanolamide, and palmitoylethanolamide), and their dominating lipid precursor’s phosphatidylcholines. Biomolecule profiles were measured at the onset of first-episode psychosis (FEP) and 0.6 years and 5.1 years after the initiation of AP treatment. The results indicated that FEP might be characterized by elevated concentrations of NAEs and by decreased 2-AG levels. At this stage of the disease, the NAE-mediated upregulation of peroxisome proliferator-activated receptors (PPARs) manifested themselves in energy expenditure. A 5-year disease progression and AP treatment adverse effects led to a robust increase in 2-AG levels, which contributed to strengthened cannabinoid (CB1) receptor-mediated effects, which manifested in obesity. Dynamic 2-AG, NAEs, and their precursors in terms of phosphatidylcholines are relevant to the description of the metabolic shifts resulting from the altered eECS function during and after FEP.

Intoduction: The ventral pallidum (VP) plays a distinct role in reward-related learning. Since the cannabinoid CB1 and mu-opioid receptors are expressed in the VP, the presynaptic CB1 receptors may be involved in the activity of the endogenous opioid reward system. The prefrontal cortex (PFC) contributes to the changes in synaptic plasticity under drug abuse and interestingly, is neuroanatomically connected to the VP. MicroRNAs (miRNAs) as valuable biomarkers mediate the expression level of brain-derived neurotrophic factor (BDNF) in the PFC. The present study aimed to investigate the contributions of the PFC miRNA-10a-5p and BDNF in the interaction between the opioidergic and ventral pallidal endocannabinoid systems in the conditioned place preference procedure to assess the drugs’ rewarding properties. Methods and Materials: Adult male Wistar rats were bilaterally cannulated into the VP by stereotaxic surgery. Intraperitoneal administration of morphine was done via a 3-day schedule of conditioned place preference (CPP) paradigm. The different doses of AM251, as a selective antagonist of cannabinoid CB1 receptors, were injected into the VP during the conditioning phase. The real-time PCR technique was used to measure the expression levels of miR-10a-5p and BDNF mRNA under the drug administrations. Results: The results showed that morphine produced a significant CPP during the conditioning phase. Intra-VP microinjection of AM251 did not induce CPP by itself. Interestingly, intra-ventral pallidal microinjection of AM251 inhibited the morphine-induced CPP. The locomotor activity did not change in all experimental groups. The RT-PCR results showed the induction of morphine-induced reward and its suppression by inhibiting the ventral pallidal endocannabinoid system changed the PFC BDNF mRNA and miR-10a-5p. Conclusions: These results indicate that the ventral pallidal endocannabinoid system may be involved in morphine-induced CPP. The PFC expression changes of BDNF mRNA and miR-10a-5p may be associated with the inhibitory effect of the VP CB1 receptors on morphine reward. [ABSTRACT FROM AUTHOR]

Objective: Obesity-induced accumulation of ectopic fat in the liver is thought to contribute to the development of insulin resistance, and increased activity of hepatic CB1R has been shown to promote both processes. However, lipid accumulation in liver can be experimentally dissociated from insulin resistance under certain conditions, suggesting the involvement of additional mechanisms. Obesity is also associated with pro-inflammatory changes which, in turn, can promote insulin resistance. Kupffer cells (KCs), the liver's resident macrophages, are the major source of pro-inflammatory cytokines in the liver, such as TNF-α, which has been shown to inhibit insulin signaling in multiple cell types, including hepatocytes. Here, we sought to identify the role of CB1R in KCs in obesity-induced hepatic insulin resistance. Methods: We used intravenously administered β-D-glucan-encapsulated siRNA to knock-down CB1R gene expression selectively in KCs. Results: We demonstrate that a robust knock-down of the expression of Cnr1, the gene encoding CB1R, results in improved glucose tolerance and insulin sensitivity in diet-induced obese mice, without affecting hepatic lipid content or body weight. Moreover, Cnr1 knock-down in KCs was associated with a shift from pro-inflammatory M1 to anti-inflammatory M2 cytokine profile and improved insulin signaling as reflected by increased insulin-induced Akt phosphorylation. Conclusion: These findings suggest that CB1R expressed in KCs plays a critical role in obesity-related hepatic insulin resistance via a pro-inflammatory mechanism.

Introduction: Previous studies have shown that the cannabinoid system is involved in anxiety.In addition, transient receptor potential vanilloid type-1 (TRPV1) channels are new targets for the development of anxiolytics. The present study investigated the possible interaction between the cannabinoid and vanilloid systems on anxiety-like behavior in rats. Methods: Four different groups of male Wistar rats received intraperitoneal (IP) injections of (1) vehicle (DMSO+saline), (2) cannabinoid receptor agonist WIN55212-2 (WIN)(1 mg/kg), (3) TRPV1 receptor antagonist capsazepine (CPZ) (5 mg/kg), or (4) combined WIN (1 mg/kg) and CPZ (5 mg/kg) treatment 30 min before testing in the elevated plus maze. Results: The results showed that compared to the control (vehicle), both WIN and CPZ increased the time spent and number of entries on the open arms. Co-administration of WIN and CPZ had a synergistic effect, i.e., the number of entries and time spent on the open arms was greater than that in the groups administered the two compounds alone. The total distance travelled by rats and total number of entries on to the arms did not significantly difer between groups. Conclusion: Acute neuropharmacological blockade of the TRPV1 receptor or stimulation of the CB1 receptor produced an anxiolytic effect. It seems that antagonism of the vanilloid system modulates cannabinoid outputs that increase the anxiolytic effect. TRPV1 antagonism may alter endocannabinoids production, which in turn enhances anxiolytic effect. These results suggest interaction of two systems or sharing some signaling pathways that affect anxiety expression.

In male rats, copulation to satiety induces a long-lasting sexual inhibitory state, considered to rely on a decreased sexual motivation. Dopaminergic transmission at the mesolimbic system plays a central role in the regulation of male sexual motivation. Endocannabinoids (eCBs) modulate the activity of the mesolimbic system and both dopamine (DA) and cannabinoid receptor activation reverses the sexual inhibition that characterizes sexually satiated rats. The eCB anandamide reverses sexual satiety when systemically administered or infused into the ventral tegmental area (VTA), the region where the activity of mesolimbic dopaminergic neurons is regulated. Thus, it could be thought that sexual motivation is diminished during the long-lasting sexual inhibition of sexually satiated rats and that eCBs reverse that inhibition through the modulation of the dopaminergic system. To test this hypothesis, we assessed the motivational state of sexually satiated male rats and determined if 2-arachidonoylglycerol (2-AG), the most abundant eCB and a full cannabinoid receptor agonist, also reversed the sexual inhibitory state. To establish the possible interaction between 2-AG and anandamide with the dopaminergic system for the reversal of sexual satiety, we analyzed the effects of the co-administration of each eCB and DA receptor agonists or antagonists. Results showed that 24-h after copulation to satiety, when the sexual inhibition is well established, the males’ sexual motivation is diminished as measured in the sexual incentive motivation test. 2-AG, similarly to anandamide, reverses sexual satiety through the activation of CB1 receptors and both eCBs interact with the dopaminergic system to reverse the sexual inhibitory state. 2-AG effects are mediated by the modulation of the D2-like DA receptor family, whereas anandamide’s effects are clearly mediated by the modulation of the D1-like DA receptor family and the activation of D2-like DA receptors. Present results evidence that a reduced sexual motivation underlies the sexual inhibitory state of sexually satiated rats and support the notion that eCBs reverse sexual satiety by modulating dopaminergic transmission, presumably at the mesolimbic system. Anandamide and 2-AG have a different interaction with D1-like and D2-like DA receptor families. Altogether present data endorse the association of the eCB system with the regulation of the motivational tone at the mesolimbic system.

Huntington’s disease (HD) is a heritable neurological disorder that affects cognitive and motor performance in patients carrying the mutated huntingtin (HTT) gene. In mouse models of HD, previous reports showed a significant increase in spontaneous GABAA receptor-mediated synaptic activity in striatal spiny projection neurons (SPNs). In this study, using optogenetics and slice electrophysiology, we examined the contribution of γ-aminobutyric acid (GABA)-ergic parvalbumin (PV)- and somatostatin (SOM)-expressing interneurons to the increase in GABA neurotransmission using the Q175 (heterozygote) mouse model of HD. Patch clamp recordings in voltage-clamp mode were performed on SPNs from brain slices of presymptomatic (2 months) and symptomatic (8 and 12 months) Q175 mice and wildtype (WT) littermates. While inhibitory postsynaptic currents (IPSCs) evoked in SPNs following optical activation of PV- and SOM-expressing interneurons differed in amplitude, no genotype-dependent differences were observed at all ages from both interneuron types; however, responses evoked by either type were found to have faster kinetics in symptomatic mice. Since SOM-expressing interneurons are constitutively active in striatal brain slices, we then examined the effects of acutely silencing these neurons in symptomatic mice with enhanced Natronomonas pharaonis halorhodopsin (eNpHR). Optically silencing SOM-expressing interneurons resulted in a greater decrease in the frequency of spontaneous IPSCs (sIPSCs) in a subset of SPNs from Q175 mice compared to WTs, suggesting that SOM-expressing interneurons are the main contributors to the overall increased GABA synaptic activity in HD SPNs. Additionally, the effects of activating GABAB and cannabinoid (CB1) receptors were investigated to determine whether these receptors were involved in modulating interneuron-specific GABA synaptic transmission and if this modulation differed in HD mice. When selectively activating PV- and SOM-expressing interneurons in the presence of the CB1 receptor agonist WIN-55,212, the magnitudes of the evoked IPSCs in SPNs decreased for both interneuron types although this change was less prominent in symptomatic Q175 SPNs during SOM-expressing interneuron activation. Overall, these findings show that dysfunction of SOM-expressing interneurons contributes to the increased GABA synaptic activity found in HD mouse models and that dysregulation of the endocannabinoid system may contribute to this effect.

In male rats, copulation to satiety induces a long-lasting sexual inhibitory state, considered to rely on a decreased sexual motivation. Dopaminergic transmission at the mesolimbic system plays a central role in the regulation of male sexual motivation. Endocannabinoids (eCBs) modulate the activity of the mesolimbic system and both dopamine (DA) and cannabinoid receptor activation reverses the sexual inhibition that characterizes sexually satiated rats. The eCB anandamide reverses sexual satiety when systemically administered or infused into the ventral tegmental area (VTA), the region where the activity of mesolimbic dopaminergic neurons is regulated. Thus, it could be thought that sexual motivation is diminished during the long-lasting sexual inhibition of sexually satiated rats and that eCBs reverse that inhibition through the modulation of the dopaminergic system. To test this hypothesis, we assessed the motivational state of sexually satiated male rats and determined if 2-arachidonoylglycerol (2-AG), the most abundant eCB and a full cannabinoid receptor agonist, also reversed the sexual inhibitory state. To establish the possible interaction between 2-AG and anandamide with the dopaminergic system for the reversal of sexual satiety, we analyzed the effects of the co-administration of each eCB and DA receptor agonists or antagonists. Results showed that 24-h after copulation to satiety, when the sexual inhibition is well established, the males' sexual motivation is diminished as measured in the sexual incentive motivation test. 2-AG, similarly to anandamide, reverses sexual satiety through the activation of CB1 receptors and both eCBs interact with the dopaminergic system to reverse the sexual inhibitory state. 2-AG effects are mediated by the modulation of the D2-like DA receptor family, whereas anandamide's effects are clearly mediated by the modulation of the D1-like DA receptor family and the activation of D2-like DA receptors. Present results evidence that a reduced sexual motivation underlies the sexual inhibitory state of sexually satiated rats and support the notion that eCBs reverse sexual satiety by modulating dopaminergic transmission, presumably at the mesolimbic system. Anandamide and 2-AG have a different interaction with D1-like and D2-like DA receptor families. Altogether present data endorse the association of the eCB system with the regulation of the motivational tone at the mesolimbic system. [ABSTRACT FROM AUTHOR]

The taste of sucrose is commonly used to provide pain relief in newborn humans and is innately analgesic to neonatal rodents. In adulthood, sucrose remains a strong motivator to feed, even in potentially hazardous circumstances (ie, threat of tissue damage). However, the neurobiological mechanisms of this endogenous reward-pain interaction are unclear. We have developed a simple model of sucrose drinking-induced analgesia in Sprague-Dawley rats (6-10 weeks old) and have undertaken a behavioral and pharmacological characterization using the Hargreaves' test of hind-paw thermal sensitivity. Our results reveal an acute, potent, and robust inhibitory effect of sucrose drinking on thermal nociceptive behaviour that unlike the phenomenon in neonates is independent of endogenous opioid signalling and does not seem to operate through classical descending inhibition of the spinal cord circuitry. Experience of sucrose drinking had a conditioning effect whereby the apparent expectancy of sucrose enabled water alone (in euvolemic animals) to elicit a short-lasting placebo-like analgesia. Sweet taste alone, however, was insufficient to elicit analgesia in adult rats intraorally perfused with sucrose. Instead, the sucrose analgesia phenomenon only appeared after conditioning by oral perfusion in chronically cannulated animals. This sucrose analgesia was completely prevented by systemic dosing of the endocannabinoid CB1 receptor antagonist rimonabant. These results indicate the presence of an endogenous supraspinal analgesic circuit that is recruited by the context of rewarding drinking and is dependent on endocannabinoid signalling. We propose that this hedonic sucrose-drinking model may be useful for further investigation of the supraspinal control of pain by appetite and reward. [ABSTRACT FROM AUTHOR]