Effect of Fatty Acid Amide Hydrolase Inhibitor URB597 on Orofacial Pain Perception in Rats.

Endocannabinoids act as analgesic agents in a number of headache models. However, their effectiveness varies with the route of administration and the type of pain. In this study, we assessed the role of the fatty acid amide hydrolase inhibitor URB597 in an animal model of orofacial pain based on tooth pulp stimulation. More specifically, we assessed the effects of intracerbroventricular (i.c.v.) and intraperitoneal (i.p.) administration of URB597 on the amplitude of evoked tongue jerks (ETJ) in rats. The levels of the investigated mediators anandamide (AEA), 2-arachidonyl glycerol (2-AG), Substance P (SP), calcitonin-gene-related peptide (CGRP), endomorphin-2 (EM-2) and fatty acid amide hydrolase (FAAH) inhibitor by URB597 and receptors cannabinoid type-1 receptors (CB1R), cannabinoid type-2 receptors (CB2R) and µ-opioid receptors (MOR) were determined in the mesencephalon, thalamus and hypothalamus tissues. We have shown that increasing endocannabinoid AEA levels by both central and peripheral inhibition of FAAH inhibitor by URB597 has an antinociceptive effect on the trigemino-hypoglossal reflex mediated by CB1R and influences the activation of the brain areas studied. On the other hand, URB597 had no effect on the concentration of 2-AG in the examined brain structures and caused a significant decrease in CB2R mRNA expression in the hypothalamus only. Tooth pulp stimulation caused in a significant increase in SP, CGRP and EM-2 gene expression in the midbrain, thalamus and hypothalamus. In contrast, URB597 administered peripherally one hour before stimulation decreased the mRNA level of these endogenous neuropeptides in comparison with the control and stimulation in all examined brain structures. Our results show that centrally and peripherally administered URB597 is effective at preventing orofacial pain by inhibiting AEA catabolism and reducing the level of CGRP, SP and EM-2 gene expression and that AEA and 2-AG have different species and model-specific regulatory mechanisms. The data presented in this study may represent a new promising therapeutic target in the treatment of orofacial pain.

Mechanistic origin of partial agonism of tetrahydrocannabinol for cannabinoid receptors.

Cannabinoid receptor 1 (CB1) is a therapeutically relevant drug target for controlling pain, obesity, and other central nervous system disorders. However, full agonists and antagonists of CB1 have been reported to cause serious side effects in patients. Therefore, partial agonists have emerged as a viable alternative as they can mitigate overstimulation and side effects. One of the key bottlenecks in the design of partial agonists, however, is the lack of understanding of the molecular mechanism of partial agonism itself. In this study, we examine two mechanistic hypotheses for the origin of partial agonism in cannabinoid receptors and predict the mechanistic basis of partial agonism exhibited by Δ9-Tetrahydrocannabinol (THC) against CB1. In particular, we inspect whether partial agonism emerges from the ability of THC to bind in both agonist and antagonist-binding poses or from its ability to only partially activate the receptor. We used extensive molecular dynamics simulations and Markov state modeling to capture the THC binding in both antagonist and agonist-binding poses in the CB1 receptor. Furthermore, we predict that binding of THC in the agonist-binding pose leads to rotation of toggle switch residues and causes partial outward movement of intracellular transmembrane helix 6 (TM6). Our simulations also suggest that the alkyl side chain of THC plays a crucial role in determining partial agonism by stabilizing the ligand in the agonist and antagonist-like poses within the pocket. Taken together, this study provides important insights into the mechanistic origin of the partial agonism of THC.

Obesity risk is associated with altered cerebral glucose metabolism and decreased µ-opioid and CB1 receptor availability.

BACKGROUND: Obesity is a pressing public health concern worldwide. Novel pharmacological means are urgently needed to combat the increase of obesity and accompanying type 2 diabetes (T2D). Although fully established obesity is associated with neuromolecular alterations and insulin resistance in the brain, potential obesity-promoting mechanisms in the central nervous system have remained elusive. In this triple-tracer positron emission tomography study, we investigated whether brain insulin signaling, µ-opioid receptors (MORs) and cannabinoid CB1 receptors (CB1Rs) are associated with risk for developing obesity. METHODS: Subjects were 41 young non-obese males with variable obesity risk profiles. Obesity risk was assessed by subjects' physical exercise habits, body mass index and familial risk factors, including parental obesity and T2D. Brain glucose uptake was quantified with [18F]FDG during hyperinsulinemic euglycemic clamp, MORs were quantified with [11C]carfentanil and CB1Rs with [18F]FMPEP-d2. RESULTS: Subjects with higher obesity risk had globally increased insulin-stimulated brain glucose uptake (19 high-risk subjects versus 19 low-risk subjects), and familial obesity risk factors were associated with increased brain glucose uptake (38 subjects) but decreased availability of MORs (41 subjects) and CB1Rs (36 subjects). CONCLUSIONS: These results suggest that the hereditary mechanisms promoting obesity may be partly mediated via insulin, opioid and endocannabinoid messaging systems in the brain.

The Peripheral Cannabinoid Receptor Type 1 (CB1) as a Molecular Target for Modulating Body Weight in Man.

The cannabinoid 1 (CB1) receptor regulates appetite and body weight; however, unwanted central side effects of both agonists (in wasting disorders) or antagonists (in obesity and diabetes) have limited their therapeutic utility. At the peripheral level, CB1 receptor activation impacts the energy balance of mammals in a number of different ways: inhibiting satiety and emesis, increasing food intake, altering adipokine and satiety hormone levels, altering taste sensation, decreasing lipolysis (fat break down), and increasing lipogenesis (fat generation). The CB1 receptor also plays an important role in the gut-brain axis control of appetite and satiety. The combined effect of peripheral CB1 activation is to promote appetite, energy storage, and energy preservation (and the opposite is true for CB1 antagonists). Therefore, the next generation of CB1 receptor medicines (agonists and antagonists, and indirect modulators of the endocannabinoid system) have been peripherally restricted to mitigate these issues, and some of these are already in clinical stage development. These compounds also have demonstrated potential in other conditions such as alcoholic steatohepatitis and diabetic nephropathy (peripherally restricted CB1 antagonists) and pain conditions (peripherally restricted CB1 agonists and FAAH inhibitors). This review will discuss the mechanisms by which peripheral CB1 receptors regulate body weight, and the therapeutic utility of peripherally restricted drugs in the management of body weight and beyond.

Fintiamin: A diketopiperazine from the marine sponge-derived fungus Eurotium sp.

The fungus Eurotium sp., derived from the marine sponge Ircinia variabilis, was found to produce a diketopiperazine-indole alkaloid that we named fintiamin (1). Structural elucidation of 1 was achieved by extensive spectroscopic analysis including nuclear magnetic resonance spectroscopy and mass spectrometry. Compound 1 is a lipophilic terpenoid-dipeptide hybrid molecule that shows affinity for the cannabinoid CB1 receptor at low micromolar concentrations. Docking studies based on previous X-ray structures provide a plausible binding pose for compound 1 in the orthosteric binding site of the CB1 receptor.

Mechanisms of endocannabinoid control of synaptic plasticity.

The endogenous cannabinoid transmitter system regulates synaptic transmission throughout the nervous system. Unlike conventional transmitters, specific stimuli induce synthesis of endocannabinoids (eCBs) in the postsynaptic neuron, and these travel backwards to modulate presynaptic inputs. In doing so, eCBs can induce short-term changes in synaptic strength and longer-term plasticity. While this eCB regulation is near ubiquitous, it displays major regional and synapse specific variations with different synapse specific forms of short-versus long-term plasticity throughout the brain. These differences are due to the plethora of pre- and postsynaptic mechanisms which have been implicated in eCB signalling, the intricacies of which are only just being realised. In this review, we shall describe the current understanding and highlight new advances in this area, with a focus on the retrograde action of eCBs at CB1 receptors (CB1Rs). This article is part of the special Issue on 'Cannabinoids'.

Cannabidiol effectively reverses mechanical and thermal allodynia, hyperalgesia, and anxious behaviors in a neuropathic pain model: Possible role of CB1 and TRPV1 receptors.

The incidence of chronic pain is high in the general population and it is closely related to anxiety disorders, which promote negative effects on the quality of life. The cannabinoid system has essential participation in the pain sensitivity circuit. In this perspective, cannabidiol (CBD) is considered a promising strategy for treating neuropathic pain. Our study aimed to evaluate the effects of sub-chronic systemic treatment with CBD (0.3, 3, 10, or 30 mg/kg, i.p.) in male in rats submitted to chronic constriction injury of the sciatic nerve (CCI) or not (SHAM) and assessed in nociceptive tests (von Frey, acetone, and hot plate, three days CBD's treatment) and in the open field test (OFT, two days CBD's treatment). We performed a screening immunoreactivity of CB1 and TRPV1 receptors in cortical and limbic regions tissues, which were collected after 1.5 h of behavioral tests on the 24th experimental day. This study presents a dose-response curve to understand better the effects of low doses (3 mg/kg) on CBD's antiallodynic and anxiolytic effects. Also, low doses of CBD were able to (1) reverse mechanical and thermal allodynia (cold) and hyperalgesia, (2) reverse anxious behaviors (reduction of the % of grooming and freezing time, and increase of the % of center time in the OFT) induced by chronic pain. The peripheral neuropathy promoted the increase in the expression of CB1 and TRPV1 receptors in the anterior cingulate cortex (ACC), anterior insular cortex (AIC), basolateral amygdala (BLA), dorsal hippocampus (DH), and ventral hippocampus (VH). CBD potentiated this effect in the ACC, AIC, BLA, DH, and VH regions. These results provide substantial evidence of the role of the ACC-AIC-BLA corticolimbic circuit, and BLA-VH for pain regulation. These results can be clinically relevant since they contribute to the evidence of CBD's beneficial effects on treating chronic pain and associated comorbidities such as anxiety.

The endocannabinoidome in neuropsychiatry: Opportunities and potential risks.

The endocannabinoid system (ECS) comprises two cognate endocannabinoid receptors referred to as CB1R and CB2R. ECS dysregulation is apparent in neurodegenerative/neuro-psychiatric disorders including but not limited to schizophrenia, major depressive disorder and potentially bipolar disorder. The aim of this paper is to review mechanisms whereby both receptors may interact with neuro-immune and neuro-oxidative pathways, which play a pathophysiological role in these disorders. CB1R is located in the presynaptic terminals of GABAergic, glutamatergic, cholinergic, noradrenergic and serotonergic neurons where it regulates the retrograde suppression of neurotransmission. CB1R plays a key role in long-term depression, and, to a lesser extent, long-term potentiation, thereby modulating synaptic transmission and mediating learning and memory. Optimal CB1R activity plays an essential neuroprotective role by providing a defense against the development of glutamate-mediated excitotoxicity, which is achieved, at least in part, by impeding AMPA-mediated increase in intracellular calcium overload and oxidative stress. Moreover, CB1R activity enables optimal neuron-glial communication and the function of the neurovascular unit. CB2R receptors are detected in peripheral immune cells and also in central nervous system regions including the striatum, basal ganglia, frontal cortex, hippocampus, amygdala as well as the ventral tegmental area. CB2R upregulation inhibits the presynaptic release of glutamate in several brain regions. CB2R activation also decreases neuroinflammation partly by mediating the transition from a predominantly neurotoxic "M1" microglial phenotype to a more neuroprotective "M2" phenotype. CB1R and CB2R are thus novel drug targets for the treatment of neuro-immune and neuro-oxidative disorders including schizophrenia and affective disorders.

Brain imaging of cannabinoid type I (CB1 ) receptors in women with cannabis use disorder and male and female healthy controls.

Cannabis effects are predominantly mediated by pharmacological actions on cannabinoid type 1 (CB1 ) receptors. Prior positron emission tomography (PET) studies in individuals who use cannabis included almost exclusively males. PET studies in females are needed because there are sex differences in cannabis effects, progression to cannabis use disorder (CUD), and withdrawal symptom severity. Females with CUD (N = 10) completed two double-blind cannabis smoking sessions (Session 1: placebo; Session 2: active), and acute cannabis effects were assessed. After Session 2, participants underwent 3 days of monitored cannabis abstinence; mood, craving, and withdrawal symptoms were assessed and a PET scan (radiotracer: [11 C]OMAR) followed. [11 C]OMAR Distribution volume (VT ) from these participants was compared with VT of age/BMI-similar female non-users of cannabis ("healthy controls"; N = 10). VT was also compared between female and male healthy controls (N = 7). Females with CUD displayed significantly lower VT than female healthy controls in specific brain regions (hippocampus, amygdala, cingulate, and insula). Amygdala VT was negatively correlated with mood changes (anger/hostility) during abstinence, but VT was not correlated with other withdrawal symptoms or cannabis effects. Among healthy controls, females had significantly higher VT than males in all brain regions examined. Chronic cannabis use appears to foster downregulation of CB1 receptors in women, as observed previously in men, and there are inherent sex differences in CB1 availability. Future studies should elucidate the time course of CB1 downregulation among females who use cannabis and examine the relation between CB1 availability and cannabis effects among other populations (e.g., infrequent users; medicinal users).

Positive allosteric modulation of type 1 cannabinoid receptors reduces spike-and-wave discharges in Genetic Absence Epilepsy Rats from Strasbourg.

Childhood Absence Epilepsy (CAE) accounts for approximately 10% of all pediatric epilepsies. Current treatments for CAE are ineffective in approximately 1/3 of patients and can be associated with severe side effects such as hepatotoxicity. Certain cannabinoids, such as cannabidiol (CBD), have shown promise in the treatment of pediatric epilepsies. However, CBD remains limited or prohibited in many jurisdictions, and has not been shown to have efficacy in CAE. Modulation of the type 1 cannabinoid receptor (CB1R) may provide more desirable pharmacological treatments. Genetic Absence Epilepsy Rats from Strasbourg (GAERS) model many aspects of CAE, including cortical spike and wave discharges (SWDs). We have recently demonstrated that Δ9-tetrahydrocannabinol (THC) increases SWDs in GAERS whereas CBD decreases these events. Here, we characterized aspects of the endocannabinoid system in brain areas relevant to seizures in GAERS and tested whether positive allosteric modulators (PAMs) of CB1R reduced SWDs. Both female and male GAERS had reduced (>50%) expression of CB1R and elevated levels of the endocannabinoid 2-AG in cortex compared to non-epileptic controls (NEC). We then administered the CB1R PAMs GAT211 and GAT229 to GAERS implanted with cortical electrodes. Systemic administration of GAT211 to male GAERS reduced SWDs by 40%. Systemic GAT229 administration reduced SWDs in female and male GAERS. Intracerebral infusion of GAT229 into the cortex of male GAERS reduced SWDs by >60% in a CB1R-dependent manner that was blocked by SR141716A. Together, these experiments identify altered endocannabinoid tone in GAERS and suggest that CB1R PAMs should be explored for treatment of absence seizures.

A Cannabinoid-1 Receptor Antagonist MJ08 with Different Effects in Stomach and Small Intestine.

Background:To investigate the inverse agonistic effect of a novel type 1 cannabinoid (CB1) receptor antagonist, MJ08, on the gastrointestinal tract (GIT).Methods: In vivo, carbon propulsion within the stomach of mice was undertaken to investigate the effects of MJ08. In vitro, the effects of MJ08 were investigated on the contraction of smooth muscle on the isolated gastric fundus, gastric body, duodenum, jejunum, and ileum.Results:Western blotting results showed that MJ08 (0.62 mg/kg body weight) reversed WIN55,212-2 (1.0 mg/kg)-induced reduction of carbon transit. MJ08 (1.25, 2.5 mg/kg) stimulated carbon transit dose dependently, demonstrating an inverse agonistic effect. In vitro experiments showed that the expression of MJ08 increased the contraction of small intestine, and that its inverse agonistic effect was significantly stronger than that of SR141716A, but no effect was noted on the gastric body. Western blotting showed that the MJ08 increased the expression of CB1 receptor in different GIT segments.Conclusion:MJ08 is not only an antagonist but also an inverse agonist of the CB1 receptor. MJ08 and SR141716A can enhance motility in the small intestine and increase the expression of CB1 receptor in the small intestine.

Cannabinoid type 1 receptors in A2a neurons contribute to cocaine-environment association.

RATIONALE: Cannabinoid type 1 receptors (CB1Rs) are widely expressed within the brain's reward circuits and are implicated in regulating drug induced behavioral adaptations. Understanding how CB1R signaling in discrete circuits and cell types contributes to drug-related behavior provides further insight into the pathology of substance use disorders. OBJECTIVE AND METHODS: We sought to determine how cell type-specific expression of CB1Rs within striatal circuits contributes to cocaine-induced behavioral plasticity, hypothesizing that CB1R function in distinct striatal neuron populations would differentially impact behavioral outcomes. We crossed conditional Cnr1fl/fl mice and striatal output pathway cre lines (Drd1a -cre; D1, Adora2a -cre; A2a) to generate cell type-specific CB1R knockout mice and assessed their performance in cocaine locomotor and associative behavioral assays. RESULTS: Both knockout lines retained typical locomotor activity at baseline. D1-Cre x Cnr1fl/fl mice did not display hyperlocomotion in response to acute cocaine dosing, and both knockout lines exhibited blunted locomotor activity across repeated cocaine doses. A2a-cre Cnr1fl/fl, mice did not express a preference for cocaine paired environments in a two-choice place preference task. CONCLUSIONS: This study aids in mapping CB1R-dependent cocaine-induced behavioral adaptations onto distinct striatal neuron subtypes. A reduction of cocaine-induced locomotor activation in the D1- and A2a-Cnr1 knockout mice supports a role for CB1R function in the motor circuit. Furthermore, a lack of preference for cocaine-associated context in A2a-Cnr1 mice suggests that CB1Rs on A2a-neuron inhibitory terminals are necessary for either reward perception, memory consolidation, or recall. These results direct future investigations into CB1R-dependent adaptations underlying the development and persistence of substance use disorders.

Antipsychotic potential of the type 1 cannabinoid receptor positive allosteric modulator GAT211: preclinical in vitro and in vivo studies.

RATIONALE: Antipsychotics help alleviate the positive symptoms associated with schizophrenia; however, their debilitating side effects have spurred the search for better treatment options. Novel compounds can be screened for antipsychotic potential in neuronal cell cultures and following acute N-methyl-D-aspartate (NMDA) receptor blockade with non-competitive antagonists such as MK-801 in rodent behavioral models. Given the known interactions between NMDA receptors and type 1 cannabinoid receptors (CB1R), compounds that modulate CB1Rs may have therapeutic potential for schizophrenia. OBJECTIVES: This study assessed whether the CB1R positive allosteric modulator GAT211, when compared to ∆9-tetrahydrocannabinol (THC), has potential to reduce psychiatric behavioral phenotypes following acute MK-801 treatment in rats, and block hyperdopaminergic signalling associated with those behaviors. METHODS: The effects of GAT211 and THC on cellular signaling were compared in Neuro2a cells, and behavioral effects of GAT211 and THC on altered locomotor activity and prepulse inhibition of the acoustic startle response caused by acute MK-801 treatment were assessed in male, Long Evans rats. RESULTS: GAT211 limited dopamine D2 receptor-mediated extracellular regulated kinase (ERK) phosphorylation in Neuro2a cells, whereas THC did not. As expected, acute MK-801 (0.15 mg/kg) produced a significant increase in locomotor activity and impaired PPI. GAT211 treatment alone (0.3-3.0 mg/kg) dose-dependently reduced locomotor activity and the acoustic startle response. GAT211 (3.0 mg/kg) also prevented hyperlocomotion caused by MK-801 but did not significantly affect PPI impairments. CONCLUSION: Taken together, these findings support continued preclinical research regarding the usefulness of CB1R positive allosteric modulators as antipsychotics.

CB1 Receptor Signaling Modulates Amygdalar Plasticity during Context-Cocaine Memory Reconsolidation to Promote Subsequent Cocaine Seeking.

Contextual drug-associated memories precipitate craving and relapse in cocaine users. Such associative memories can be weakened through interference with memory reconsolidation, a process by which memories are maintained following memory retrieval-induced destabilization. We hypothesized that cocaine-memory reconsolidation requires cannabinoid type 1 receptor (CB1R) signaling based on the fundamental role of the endocannabinoid system in synaptic plasticity and emotional memory processing. Using an instrumental model of cocaine relapse, we evaluated whether systemic CB1R antagonism (AM251; 3 mg/kg, i.p.) during memory reconsolidation altered (1) subsequent drug context-induced cocaine-seeking behavior as well as (2) cellular adaptations and (3) excitatory synaptic physiology in the basolateral amygdala (BLA) in male Sprague Dawley rats. Systemic CB1R antagonism, during, but not after, cocaine-memory reconsolidation reduced drug context-induced cocaine-seeking behavior 3 d, but not three weeks, later. CB1R antagonism also inhibited memory retrieval-associated increases in BLA zinc finger 268 (zif268) and activity regulated cytoskeletal-associated protein (Arc) immediate-early gene (IEG) expression and changes in BLA AMPA receptor (AMPAR) and NMDA receptor (NMDAR) subunit phosphorylation that likely contribute to increased receptor membrane trafficking and synaptic plasticity during memory reconsolidation. Furthermore, CB1R antagonism increased memory reconsolidation-associated spontaneous EPSC (sEPSC) frequency in BLA principal neurons during memory reconsolidation. Together, these findings suggest that CB1R signaling modulates cellular and synaptic mechanisms in the BLA that may facilitate cocaine-memory strength by enhancing reconsolidation or synaptic reentry reinforcement, or by inhibiting extinction-memory consolidation. These findings identify the CB1R as a potential therapeutic target for relapse prevention.SIGNIFICANCE STATEMENT Drug relapse can be triggered by the retrieval of context-drug memories on re-exposure to a drug-associated environment. Context-drug associative memories become destabilized on retrieval and must be reconsolidated into long-term memory stores to persist. Hence, targeted interference with memory reconsolidation can weaken maladaptive context-drug memories and reduce the propensity for drug relapse. Our findings indicate that cannabinoid type 1 receptor (CB1R) signaling is critical for context-cocaine memory reconsolidation and subsequent drug context-induced reinstatement of cocaine-seeking behavior. Furthermore, cocaine-memory reconsolidation is associated with CB1R-dependent immediate-early gene (IEG) expression and changes in excitatory synaptic proteins and physiology in the basolateral amygdala (BLA). Together, our findings provide initial support for CB1R as a potential therapeutic target for relapse prevention.

Synthetic cannabis: adverse events reported to the New Zealand Pharmacovigilance Centre.

INTRODUCTION: Synthetic Cannabinoid Receptor Agonists (SCRA) were legally available in New Zealand (NZ) prior to May 2014. During the period November 2012-November 2019, reports of adverse events associated with SCRA use from across the country were submitted to the New Zealand Pharmacovigilance Centre (NZPhvC). The purpose of this study was to investigate adverse reactions associated with SCRA reported to the NZPhvC. METHODS: The NZPhvC database was searched for adverse events involving SCRA. Cases were extracted and analysed for demographic information of users, reactions reported and SCRA involved. Summary statistics were performed using SAS 9.3. RESULTS: One hundred and thirteen cases were identified from 1 November 2012 to 31 November 2019, comprising 81 males (71.7%) and 32 females (28.3%), with a mean age of 28.4 ± 10.1 years. Ethnicity included European (51.3%, n = 58), Maori (39.8%, n = 45), Indian (1.8%, n = 2), and Polynesian (0.9%, n = 1). There were a total of 327 reactions recorded in these cases, and the majority were psychiatric (52%, n = 170), followed by nervous system (11%, n = 35), alimentary (7%, n = 24), and cardiovascular (7%, n = 23). Where the compounds could be identified, the majority of events involved AB-FUBINACA (n = 18), 5 F-PB-22 (n = 17), and PB-22 (n = 6). CONCLUSIONS: This study found that young, male and European populations frequently were involved in SCRA adverse events. A disproportionate number of Maori were present in this group. Psychiatric reactions were of clinical significance, and possibly correlated to the high potency and efficacy of SCRA compared to cannabis. Pharmacovigilance is a useful tool to measure and monitor illicit drug use, and with appropriate infrastructure and capacity has the potential to contribute to drug policy at a national level.

Transcranial direct current stimulation (tDCS) produce anti-anxiety response in acute stress exposure rats via activation of amygdala CB1R.

Anxiety is one of the most common mental disorders worldwide. Currently, the main anti-anxiety drugs, selective serotonin/noradrenalin reuptake inhibitors (SSRIs/SNRIs), are always associated with delayed onset of action and low therapeutic response rate. Benzodiazepines can produce rapid effects, but their long-term use may result in severe adverse reaction and drug dependence. Transcranial direct current stimulation (tDCS) is one of the noteworthy noninvasive brain stimulation techniques and is expected to be a new choice of anti-anxiety therapy. However, the underlying mechanism remains unclear. In our recent published study, we have observed the important role of endogenous cannabinoid in the pathophysiology and treatment of anxiety. Here we verified the anti-anxiety effects of tDCS in the acute stress exposure rats, and investigated the possible role of amygdala cannabinoid receptor 1 (CB1R) activation in the anti-anxiety response of tDCS. Forced swimming exposure produced anxiety-like behaviors, which can be reversed by tDCS treatment. tDCS increased the time spent in the center without affection of locomotor activity in open field test (OFT) and elevated the number of entries into open arm and time spent in open arm in elevated plus maze test (EPMT). However, Inhibition of CB1R function by AM251 intraperitoneal injection or CB1R knockdown in amygdala produced the negative effects on the anti-anxiety action of tDCS. In conclusion, tDCS may play an anti-anxiety role at least partly via activation of amygdala CB1R, which provides a theoretical basis for the clinical application of tDCS in the treatment of anxiety disorder.

Cannabis points to the synaptic pathology of mental disorders: how aberrant synaptic components disrupt the highest psychological functions
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Cannabis can elicit an acute psychotic reaction, and its long-term use is a risk factor for schizophrenia. The main active psychoactive ingredient ∆9-tetrahydrocannabinol (Δ9-THC) activates cannabinoid 1 (CB1) receptors, which are localized to the terminals of glutamate and GABA neurons in the brain. The endogenous cannabinoids are involved in information processing and plasticity at synapses in the hippocampus, basal ganglia, and cerebral cortex. Exogenously applied CB1 receptor agonists disrupt neuronal dynamics and synaptic plasticity, resulting in cognitive deficits and impairment of the highest psychological functions. Various other pro-psychotic drugs, such as ketamine and methamphetamine, exert their effects in the same microdomain of synaptic spines as Δ9-THC. Additionally, many of the most robust findings in psychiatric genetics include components that localize to dendritic spines and have important roles in information processing and plasticity.
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La cannabis puede provocar una reacción psicótica aguda y su empleo a largo plazo es un factor de riesgo para esquizofrenia. El principal componente psicoactivo ∆9-tetrahidrocannabinol (Δ9-THC) estimula los receptores cannabinoides CB1, que se localizan en las terminales de las neuronas de glutamato y de GABA cerebrales. Los cannabinoides endógenos participan en el procesamiento de la información y la plasticidad en las sinapsis del hipocampo, los ganglios basales y la corteza cerebral. Los agonistas de CB1 administrados de forma exógena interrumpen la dinámica neuronal y la plasticidad sináptica, lo que se traduce en déficits cognitivos y deterioro de las funciones psicológicas más altas. Varias otras drogas propsicóticas, como la ketamina y la metanfetamina, ejercen sus efectos en el mismo microdominio de espinas sinápticas que el Δ9-THC. Además, muchos de los hallazgos más consistentes en genética psiquiátrica incluyen componentes que se localizan en las espinas dendríticas y tienen funciones importantes en el procesamiento y la plasticidad de la información.

Le cannabis peut provoquer une réaction psychotique aiguë et sa consommation à long terme est un facteur de risque de schizophrénie. Le ∆9-tétrahydrocannabinol (Δ9-THC), principal ingrédient psychoactif, active les récepteurs cannabinoïdes CB1 situés aux extrémités des neurones glutamatergiques et GABAergiques dans le cerveau. Les cannabinoïdes endogènes participent au traitement de l'information et à la plasticité des synapses dans l'hippocampe, les ganglions de la base et le cortex cérébral. Les agonistes CB1 exogènes perturbent la dynamique neuronale et la plasticité synaptique, entraînant des déficits cognitifs et une altération des fonctions psychologiques les plus hautes. D'autres drogues propsychotiques, telles la kétamine et la méthamphétamine, agissent dans le même micro-domaine des épines synaptiques que le Δ9-THC. De plus, de nombreuses recherches en génétique psychiatrique ont mis en évidence des composés qui jouent un rôle important dans le traitement de l'information et la plasticité en se fixant sur les épines dendritiques.

In vitro characterization of new psychoactive substances at the µ-opioid, CB1, 5HT1A, and 5-HT2A receptors-On-target receptor potency and efficacy, and off-target effects.

New psychoactive substances (NPS) appear on the recreational market on a monthly basis, with unclear toxicology, resulting in an increasing number of fatalities. Identification of drug targets and potencies is crucial for understanding and treating intoxications and for scheduling processes. In this study 60 NPS and metabolites belonging to opioids, cannabinoids and serotonergic hallucinogens classes were screened for in vitro activation of the µ-opioid, CB1, 5-HT1A and 5-HT2A receptors using the AequoZen cell system. Fentanyl and NBOMe analogues were chosen for full dose-response characterization of the µ-opioid and 5-HT2A receptors, respectively. Most substances activated their corresponding target receptor. The most potent µ-opioid receptor agonists were 2-fluorofentanyl (EC50 = 1.0 nM), carfentanil (EC50 = 2.7 nM) and acrylfentanyl (EC50 = 2.8 nM) and in total a >1500-fold difference was seen among the tested compounds. Moreover, furanylfentanyl, 4-methoxybutyrylfentanyl and valerylfentanyl acted as partial agonists of the µ-receptor. On the 5-HT2A receptor, bromo-dragonfly showed the highest potency (EC50 = 0.05 nM, 400 times more potent than LSD), followed by most NBOMe compounds with EC50 values ranging from 0.11 nM (for 25N-NBOMe) to 1.3 nM (for 25T4-NBOMe)). Off-target activation of the µ-opioid receptor was identified for piperazines, phenethylamines (in particular NBOMe and 2C compounds) and tryptamines. Moreover, the synthetic cannabinoid metabolite 3-carboxy indole PB-22 activated the 5-HT2A receptor. Bromo-dragonfly was the only compound that activated all four receptors. These results highlight the possible interplay of known and unknown NPS targets and unveil its complexity. Moreover, the detailed, quantitative information presented facilitates our further understanding of NPS toxicology.

Endocannabinoid signaling regulates the reinforcing and psychostimulant effects of ketamine in mice.

The abuse potential of ketamine limits its clinical application, but the precise mechanism remains largely unclear. Here we discovered that ketamine significantly remodels the endocannabinoid-related lipidome and activates 2-arachidonoylglycerol (2-AG) signaling in the dorsal striatum (caudate nucleus and putamen, CPu) of mice. Elevated 2-AG in the CPu is essential for the psychostimulant and reinforcing effects of ketamine, whereas blockade of the cannabinoid CB1 receptor, a predominant 2-AG receptor, attenuates ketamine-induced remodeling of neuronal dendrite structure and neurobehaviors. Ketamine represses the transcription of the monoacylglycerol lipase (MAGL) gene by promoting the expression of PRDM5, a negative transcription factor of the MAGL gene, leading to increased 2-AG production. Genetic overexpression of MAGL or silencing of PRDM5 expression in the CPu robustly reduces 2-AG production and ketamine effects. Collectively, endocannabinoid signaling plays a critical role in mediating the psychostimulant and reinforcing properties of ketamine.

Cannabinoid receptor subtype influence on neuritogenesis in human SH-SY5Y cells.

Human SH-SY5Y neuroblastoma cells stably expressing exogenous CB1 (CB1XS) or CB2 (CB2XS) receptors were developed to investigate endocannabinoid signaling in the extension of neuronal projections. Expression of cannabinoid receptors did not alter proliferation rate, viability, or apoptosis relative to parental SH-SY5Y. Transcripts for endogenous cannabinoid system enzymes (diacylglycerol lipase, monoacylglycerol lipase, α/ß-hydrolase domain containing proteins 6 and 12, N-acyl phosphatidylethanolamine-phospholipase D, and fatty acid amide hydrolase) were not altered by CB1 or CB2 expression. Endocannabinoid ligands 2-arachidonoylglycerol (2-AG) and anandamide were quantitated in SH-SY5Y cells, and diacylglycerol lipase inhibitor tetrahydrolipstatin decreased 2-AG abundance by 90% but did not alter anandamide abundance. M3 muscarinic agonist oxotremorine M, and inhibitors of monoacylglycerol lipase and α/ß hydrolase domain containing proteins 6 &12 increased 2-AG abundance. CB1 receptor expression increased lengths of short (<30 µm) and long (>30 µm) projections, and this effect was significantly reduced by tetrahydrolipstatin, indicative of stimulation by endogenously produced 2-AG. Pertussis toxin, Gßγ inhibitor gallein, and ß-arrestin inhibitor barbadin did not significantly alter long projection length in CB1XS, but significantly reduced short projections, with gallein having the greatest inhibition. The rho kinase inhibitor Y27632 increased CB1 receptor-mediated long projection extension, indicative of actin cytoskeleton involvement. CB1 receptor expression increased GAP43 and ST8SIA2 mRNA and decreased ITGA1 mRNA, whereas CB2 receptor expression increased NCAM and SYT mRNA. We propose that basal endogenous production of 2-AG provides autocrine stimulation of CB1 receptor signaling through Gi/o, Gßγ, and ß-arrestin mechanisms to promote neuritogenesis, and rho kinase influences process extension.