Δ(9)-Tetrahydrocannabinol acts as a partial agonist/antagonist in mice

Exploring the versatile roles of the endocannabinoid system and phytocannabinoids in modulating bacterial infections

The endocannabinoid system (ECS), initially identified for its role in maintaining homeostasis, particularly in regulating brain function, has evolved into a complex orchestrator influencing various physiological processes beyond its original association with the nervous system. Notably, an expanding body of evidence emphasizes the ECS's crucial involvement in regulating immune responses. While the specific role of the ECS in bacterial infections remains under ongoing investigation, compelling indications suggest its active participation in host-pathogen interactions. Incorporating the ECS into the framework of bacterial pathogen infections introduces a layer of complexity to our understanding of its functions. While some studies propose the potential of cannabinoids to modulate bacterial function and immune responses, the outcomes inherently hinge on the specific infection and cannabinoid under consideration. Moreover, the bidirectional relationship between the ECS and the gut microbiota underscores the intricate interplay among diverse physiological processes. The ECS extends its influence far beyond its initial discovery, emerging as a promising therapeutic target across a spectrum of medical conditions, encompassing bacterial infections, dysbiosis, and sepsis. This review comprehensively explores the complex roles of the ECS in the modulation of bacteria, the host's response to bacterial infections, and the dynamics of the microbiome. Special emphasis is placed on the roles of cannabinoid receptor types 1 and 2, whose signaling intricately influences immune cell function in microbe-host interactions.

Emerging pharmacotherapy for the treatment of cannabis use disorder

INTRODUCTION

About one-fifth of cannabis users, the most commonly used illicit substance, have cannabis use disorder (CUD). Psychiatric disorders and suicide are more common in these patients, and the disability-adjusted life years were reported to be 0.69 million. Pharmacotherapy for CUD is an unmet public health need, as current evidence-based therapies have limited efficacy.

AREAS COVERED

After explaining the pathophysiology of CUD, the effects of emerging pharmacological interventions in its treatment obtained from randomized controlled trials were reviewed in light of mechanisms of action. Superiority over control of cannabidiol, gabapentin, galantamine, nabilone plus zolpidem, nabiximols, naltrexone, PF-04457845, quetiapine, varenicline, and topiramate were observed through the cannabinoid, glutamatergic, γ-aminobutyric acidergic, serotonergic, noradrenergic, dopaminergic, opioidergic, and cholinergic systems. All medications were reported to be safe and tolerable.

EXPERT OPINION

Adding pharmacotherapy to psychotherapy is the optimal treatment for CUD on a case-by-case basis. Drug development to add to psychotherapy is the main path, but time and cost suggest repurposing and repositioning existing drugs. Considering sample size, follow-up, and effect size, further studies using objective tools are necessary. The future of CUD treatment is promising.

CB 1 Cannabinoid Receptor Agonists Induce Acute Respiratory Depression in Awake Mice

Recreational use of synthetic cannabinoid agonists (i.e., "Spice" compounds) that target the Cannabinoid Type 1 receptor (CB 1 ) can cause respiratory depression in humans. However, Δ 9 -tetrahydrocannabinol (THC), the major psychoactive phytocannabinoid in cannabis, is not traditionally thought to interact with CNS control of respiration, based largely upon sparse labeling of CB1 receptors in the medulla and few reports of clinically significant respiratory depression following cannabis overdose. The respiratory effects of CB 1 agonists have rarely been studied in vivo , suggesting that additional inquiry is required to reconcile the conflict between conventional wisdom and human data. Here we used whole body plethysmography to examine the respiratory effects of the synthetic high efficacy CB 1 agonist CP55,940, and the low efficacy CB 1 agonist Δ 9 -tetrahydrocannabinol in male and female mice. CP55,940 and THC, administered systemically, both robustly suppressed minute ventilation. Both cannabinoids also produced sizable reductions in tidal volume, decreasing both peak inspiratory and expiratory flow - measures of respiratory effort. Similarly, both drugs reduced respiratory frequency, decreasing both inspiratory and expiratory time while markedly increasing expiratory pause, and to a lesser extent, inspiratory pause. Respiratory suppressive effects occurred at lower doses in females than in males, and at many of the same doses shown to produce cardinal behavioral signs of CB 1 activation. We next used RNAscope in situ hybridization to localize CB 1 mRNA to glutamatergic neurons in the medullary pre-Bötzinger Complex, a critical nucleus in controlling respiration. Our results show that, contrary to previous conventional wisdom, CB 1 mRNA is expressed in glutamatergic neurons in a brain region essential for breathing and CB 1 agonists can cause significant respiratory depression.

Evaluating the Role of the Endocannabinoid System in Axon Guidance: A Literature Review

Introduction: The endocannabinoid system (ECS) mediates the actions of cannabis and has been implicated in playing critical roles in key developmental events, including axon guidance. Although several recent studies have demonstrated ECS involvement in neurodevelopment, an emphasis on its putative role in axon guidance has not been reviewed comprehensively. Objective: The purpose of this literature review is to evaluate the interrelationships between the ECS and axon guidance. Methodology: This literature review analyzes existing literature demonstrating the normal role of endocannabinoid (eCB) signaling in axon guidance, with evidence from diverse animal models. Studies were obtained from a search strategy involving terms related to the ECS and axon guidance, and cross-checking cited literature to ensure a complete evaluation. Discussion: Cannabinoid receptors, as well as eCB synthesis and degradation machinery, appear necessary for normal axon guidance during neurodevelopment. Genetic and/or pharmacological disruption of eCB signaling results in axon growth and guidance errors, implying high sensitivity to exogenous cannabinoids. Conclusion: Overall, this review highlights the intricate connections between the ECS and axon guidance in normal neurodevelopment. The mechanistic evidence discussed suggests that alterations of the ECS through genetic and pharmacological interference disrupt its normal functioning and by extension its normal role in regulating neural circuitry formation. A comprehensive understanding of this topic will be valuable in potentially uncovering the mechanisms responsible for the neurodevelopmental defects associated with pre-natal cannabis use.

UK Medical Cannabis Registry: Assessment of clinical outcomes in patients with insomnia

INTRODUCTION

The primary aim of this study was to assess changes in sleep-specific health-related quality of life (HRQoL) for those prescribed cannabis-based medicinal products (CBMPs) for insomnia.

METHODS

A case series of UK patients with insomnia was analyzed. Primary outcomes were changes in the Single-Item Sleep-Quality Scale (SQS), Generalized Anxiety Disorder-7 (GAD-7), and EQ-5D-5L at up to 6 months from baseline. Statistical significance was identified as a p value < .050.

RESULTS

61 patients were included in the analysis. There was an improvement in the SQS from baseline at 1, 3, and 6 months (p < .001). There were also improvements in the EQ-5D-5L Index value and GAD-7 at 1, 3, and 6 months (p < .050). There were 28 (45.9%) adverse events recorded by 8 patients (13.1%). There were no life-threatening/disabling adverse events.

CONCLUSION

Patients with insomnia experienced an improvement in sleep quality following the initiation of CBMPs in this medium-term analysis. Fewer than 15% of participants reported one or more adverse events. However, due to the limitations of the study design, further investigation is required before definitive conclusions can be drawn on the efficacy of CBMPs in treating insomnia.

Effects of cannabinoid agonists and antagonists in male rats discriminating the synthetic cannabinoid AM2201

The synthetic forms of delta-9-tetrahydrocannabinol (Δ9-THC), dronabinol or nabilone, have been approved to treat several indications. However, due to safety concerns their clinical utility remains limited. Consequently, there is a need for developing cannabinoid (CB) ligands that display better behavioral pharmacological profiles than Δ9-THC. Here, we utilized drug discrimination methods to compare the interoceptive effects of CB ligands that vary in potency, efficacy, and selectivity at the CB receptors, including two ligands, AM411 and AM4089, that show CB1 partial agonist-like actions in vitro. Male rats were trained to discriminate 0.1 mg/kg AM2201 from saline under a fixed-ratio (FR) 10 response schedule of food reinforcement. After establishing AM2201's discriminative-stimulus effects, pretreatment tests with the CB1 antagonist/inverse agonist rimonabant blocked AM2201's effects, whereas the peripherally-restricted antagonist AM6545 had no effect. Next, the generalization profiles of AM411 and AM4089 with CB1 full agonists (JWH-018, CP-55,940, AM8936), partial agonist (Δ9-THC), and non-cannabinoids (fentanyl, atropine) were compared. The CBs either fully (AM2201, CP-55,940, JWH-018, AM8936, Δ9-THC) or partially (AM411, AM4089) substituted for AM2201, whereas fentanyl and atropine did not produce AM2201-like effects. All CB drugs were more potent than Δ9-THC and correlation analysis confirmed that the relative behavioral potencies of CBs corresponded strongly with their relative affinities at the CB1 but not CB2 receptors. Together, our results further demonstrate that AM411 and AM4089 exhibit better pharmacological profiles compared to Δ9-THC, in that they are more potent and display in vivo partial agonist-like actions that are centrally mediated via CB1 receptors.

Molecular insights into GPCR mechanisms for drugs of abuse

Substance abuse is on the rise, and while many people may use illicit drugs mainly due to their rewarding effects, their societal impact can range from severe, as is the case for opioids, to promising, as is the case for psychedelics. Common with all these drugs' mechanisms of action are G protein-coupled receptors (GPCRs), which lie at the center of how these drugs mediate inebriation, lethality, and therapeutic effects. Opioids like fentanyl, cannabinoids like tetrahydrocannabinol, and psychedelics like lysergic acid diethylamide all directly bind to GPCRs to initiate signaling which elicits their physiological actions. We herein review recent structural studies and provide insights into the molecular mechanisms of opioids, cannabinoids, and psychedelics at their respective GPCR subtypes. We further discuss how such mechanistic insights facilitate drug discovery, either toward the development of novel therapies to combat drug abuse or toward harnessing therapeutic potential.

Associations between regular cannabis use and brain resting-state functional connectivity in adolescents and adults

BACKGROUND/AIM

Cannabis use is highly prevalent in adolescents; however, little is known about its effects on adolescent brain function.

METHOD

Resting-state functional magnetic resonance imaging was used in matched groups of regular cannabis users (N = 70, 35 adolescents: 16-17 years old, 35 adults: 26-29 years old) and non-regular-using controls (N = 70, 35 adolescents/35 adults). Pre-registered analyses examined the connectivity of seven major cortical and sub-cortical brain networks (default mode network, executive control network (ECN), salience network, hippocampal network and three striatal networks) using seed-based analysis methods with cross-sectional comparisons between user groups and age groups.

RESULTS

The regular cannabis use group (across both age groups), relative to controls, showed localised increases in connectivity only in the ECN analysis. All networks showed localised connectivity differences based on age group, with the adolescents generally showing weaker connectivity than adults, consistent with the developmental effects. Mean connectivity across entire network regions of interest (ROIs) was also significantly decreased in the ECN in adolescents. However, there were no significant interactions found between age group and user group in any of the seed-based or ROI analyses. There were also no associations found between cannabis use frequency and any of the derived connectivity measures.

CONCLUSION

Regular cannabis use is associated with changes in connectivity of the ECN, which may reflect allostatic or compensatory changes in response to regular cannabis intoxication. However, these associations were not significantly different in adolescents compared to adults.

Hippocampal expression of the cannabinoid receptor type 1 in canine epilepsy

Canine drug-resistant epilepsy is a prevailing issue in veterinary neurology. Alternative or additional treatment with cannabinoids is showing promising results in seizure management. A crucial component of the endocannabinoid system, cannabinoid receptor type 1 (CB1R), is heavily involved in the control of neurotransmitter release. Knowledge of its distribution in the epileptic brain would serve a better understanding of disease pathology and application of cannabinoids in dogs with epilepsy. CB1R distribution was assessed in sub-regions of hippocampus of dogs with idiopathic epilepsy, structural epilepsy and without cerebral pathology. In dogs with idiopathic epilepsy, significantly decreased CB1R expression compared to control animals was observed in CA1. In dogs with structural epilepsy, a significant increase in CB1R signal intensity in comparison to controls was observed. CB1R expression was higher in the structural group as compared to the idiopathic. Double immunofluorescence showed co-localization between CB1R and an astrocytic marker in about 50% of cells, regardless of the diagnosis. In summary, CB1R expression in canine hippocampus undergoes modification by the epileptic process and the direction of this change depends on the etiology of the disease. The distinct disease-associated CB1R expression needs to be considered in new treatment development for dogs with epilepsy.

Hexahydrocannabinol Pharmacology, Toxicology, and Analysis: The First Evidence for a Recent New Psychoactive Substance

BACKGROUND

During the last two years, hexahydrocannabinol (HHC), the hydrogenated derivative of tetrahydrocannabinol has been freely sold by internet websites as a "legal" replacement to THC and cannabis in a range of highly attractive branded and unbranded products, some of which are sold as "legal highs". Potentially, there could be a large demand for HHC products by individuals in Europe and internationally.

METHODS

Studies reporting HHC pharmacology, toxicology and analysis were identified from Pubmed and Scopus databases, and official international organizations' websites were considered.

RESULTS

HHC showed the effects of the typical cannabinoid on the central nervous system, with lower potency than Δ9-THC. A few studies highlighted that 9(R)-HHC is more potent than 9(S)-HHC. This molecule showed an affinity for cannabinoid receptor CB1 both in vitro and in vivo, suggesting a possible therapeutic effect in several pathologies. However, the affinity for the CB1 receptor suggests a possible addiction potential, inducing the users to misuse it. Since actual intoxication cases have not yet been reported, the HHC harmful potential was not described, probably due to the lack of effective analytical methods to detect HHC in biological matrices. Conversely, different analytical assays were developed and validated to separate HHC epimers in natural and non-natural sources.

CONCLUSION

Similarly to other NPS, the HHC represents a cheaper alternative to the controlled Δ9-THC. Its monitoring is a crucial challenge for toxicological and forensic purposes. To this concern, it is essential to further investigate HHC to support health providers in the identification of related intoxications.

A cannabinoid Hairy-Tale: Hair loss or hair gain?

BACKGROUND

Few studies have reported on the use of cannabinoid products to treat hair loss.

AIM

This article aims to reconcile cannabinoids' impact on hair growth.

METHOD

A comprehensive and structured search was conducted in PubMed and Google Scholar on June 23, 2022.

RESULT

While cannabidiol (CBD), a phytocannabinoid, may cause hair growth, several other phytocannabinoids may lead to hair loss. Additionally, the effect of CBD on hair growth may be concentration-dependent. CBD may cause hair loss at high concentrations (≥10 μM). Therefore, the concentration of CBD needs to be adjusted so that it is optimal for hair growth. One trial found that once-daily application of CBD-rich topical cannabis extract for 6 months increased nonvellus hair count by approximately 93.5% in 35 Caucasian AGA patients: 28 males aged 28-72 years [average 43 years] and 7 females aged 46-76 years [average 61 years]. Each application contained 3-4 mg of CBD. The CBD-rich topical cannabis extract was prepared by ultra-pulverizing Cannabis sativa [hemp] flower into a green chalk-like powder [10.78% CBD and 0.21% tetrahydrocannabinol] and then infusing the powder into a lanolin paste and Emu oil carrier.

CONCLUSION

Topical CBD preparations require further studies to establish their safety and efficacy profile. An ideal topical cannabinoid preparation should contain CBD at the right concentration and lack other phytocannabinoid adulterants.

The Therapeutic Potential of the Endocannabinoid System in Age-Related Diseases

The endocannabinoid system (ECS) dynamically regulates many aspects of mammalian physiology. ECS has gained substantial interest since growing evidence suggests that it also plays a major role in several pathophysiological conditions due to its ability to modulate various underlying mechanisms. Furthermore, cannabinoids, as components of the cannabinoid system (CS), have proven beneficial effects such as anti-inflammatory, immunomodulatory, neuromodulatory, antioxidative, and cardioprotective effects. In this comprehensive review, we aimed to describe the complex interaction between CS and most common age-related diseases such as neuro-degenerative, oncological, skeletal, and cardiovascular disorders, together with the potential of various cannabinoids to ameliorate the progression of these disorders. Since chronic inflammation is postulated as the pillar of all the above-mentioned medical conditions, we also discuss in this paper the potential of CS to ameliorate aging-associated immune system dysregulation.

Identification of CB1 Ligands among Drugs, Phytochemicals and Natural-Like Compounds: Virtual Screening and In Vitro Verification

Cannabinoid receptor type 1 (CB1) is an important modulator of many key physiological functions and thus a compelling molecular target. However, safe CB1 targeting is a non-trivial task. In recent years, there has been a surge of data indicating that drugs successfully used in the clinic for years (e.g. paracetamol) show CB1 activity. Moreover, there is a lot of promise in finding CB1 ligands in plants other than Cannabis sativa. In this study, we searched for possible CB1 activity among already existing drugs, their metabolites, phytochemicals, and natural-like molecules. We conducted two iterations of virtual screening, verifying the results with in vitro binding and functional assays. The in silico procedure consisted of a wide range of structure- and ligand-based methods, including docking, molecular dynamics, and quantitative structure-activity relationship (QSAR). As a result, we identified travoprost and ginkgetin as CB1 ligands, which provides a starting point for future research on the impact of their metabolites or preparations on the endocannabinoid system. Moreover, we found five natural-like compounds with submicromolar or low micromolar affinity to CB1, including one mixed partial agonist/antagonist viable for hit-to-lead phase. Finally, the computational procedure established in this work will be of use for future screening campaigns for novel CB1 ligands.

Therapeutic properties of multi-cannabinoid treatment strategies for Alzheimer’s disease

Alzheimer’s disease (AD) is a debilitating neurodegenerative disease characterized by declining cognition and behavioral impairment, and hallmarked by extracellular amyloid-β plaques, intracellular neurofibrillary tangles (NFT), oxidative stress, neuroinflammation, and neurodegeneration. There is currently no cure for AD and approved treatments do not halt or slow disease progression, highlighting the need for novel therapeutic strategies. Importantly, the endocannabinoid system (ECS) is affected in AD. Phytocannabinoids, including cannabidiol (CBD) and Δ⁹-tetrahydrocannabinol (THC), interact with the ECS, have anti-inflammatory, antioxidant, and neuroprotective properties, can ameliorate amyloid-β and NFT-related pathologies, and promote neurogenesis. Thus, in recent years, purified CBD and THC have been evaluated for their therapeutic potential. CBD reversed and prevented the development of cognitive deficits in AD rodent models, and low-dose THC improved cognition in aging mice. Importantly, CBD, THC, and other phytochemicals present in Cannabis sativa interact with each other in a synergistic fashion (the “entourage effect”) and have greater therapeutic potential when administered together, rather than individually. Thus, treatment of AD using a multi-cannabinoid strategy (such as whole plant cannabis extracts or particular CBD:THC combinations) may be more efficacious compared to cannabinoid isolate treatment strategies. Here, we review the current evidence for the validity of using multi-cannabinoid formulations for AD therapy. We discuss that such treatment strategies appear valid for AD therapy but further investigations, particularly clinical studies, are required to determine optimal dose and ratio of cannabinoids for superior effectiveness and limiting potential side effects. Furthermore, it is pertinent that future in vivo and clinical investigations consider sex effects.

Acute effects of Δ9-tetrahydrocannabinol and cannabidiol on auditory mismatch negativity

RATIONALE

Mismatch negativity (MMN) is a candidate endophenotype for schizophrenia subserved by N-methyl-D-aspartate receptor (NMDAR) function and there is increasing evidence that prolonged cannabis use adversely affects MMN generation. Few human studies have investigated the acute effects of cannabinoids on brain-based biomarkers of NMDAR function and synaptic plasticity.

OBJECTIVES

The current study investigated the acute effects of Δ⁹-tetrahydrocannabinol (THC) and cannabidiol (CBD) alone and in combination on the mismatch negativity (MMN).

METHODS

In a randomised, double-blind, crossover placebo-controlled study, 18 frequent and 18 less-frequent cannabis users underwent 5 randomised drug sessions administered via vaporiser: (1) placebo; (2) THC 8 mg; (3) CBD 400 mg; (4) THC 8 mg + CBD 4 mg [THC + CBD_low]; (5) THC 12 mg + CBD 400 mg [THC + CBD_high]. Participants completed a multifeature MMN auditory oddball paradigm with duration, frequency and intensity deviants (6% each).

RESULTS

Relative to placebo, both THC and CBD were observed to increase duration and intensity MMN amplitude in less-frequent users, and THC also increased frequency MMN in this group. The addition of low-dose CBD added to THC attenuated the effect of THC on duration and intensity MMN amplitude in less-frequent users. The same pattern of effects was observed following high-dose CBD added to THC on duration and frequency MMN in frequent users.

CONCLUSIONS

The pattern of effects following CBD combined with THC on MMN may be subserved by different underlying neurobiological interactions within the endocannabinoid system that vary as a function of prior cannabis exposure. These results highlight the complex interplay between the acute effects of exogenous cannabinoids and NMDAR function. Further research is needed to determine how this process normalises after the acute effects dissipate and following repeated acute exposure.

Translational models of cannabinoid vapor exposure in laboratory animals

Cannabis is one of the most frequently used psychoactive substances in the world. The most common route of administration for cannabis and cannabinoid constituents such as Δ-9-tetrahydrocannabinol (THC) and cannabidiol (CBD) is via smoking or vapor inhalation. Preclinical vapor models have been developed, although the vaporization devices and delivery methods vary widely across laboratories. This review examines the emerging field of preclinical vapor models with a focus on cannabinoid exposure in order to (1) summarize vapor exposure parameters and other methodological details across studies; (2) discuss the pharmacological and behavioral effects produced by exposure to vaporized cannabinoids; and (3) compare behavioral effects of cannabinoid vapor administration with those of other routes of administration. This review will serve as a guide for past and current vapor delivery methods in animals, synergize findings across studies, and propose future directions for this area of research.

Evidence for spontaneous cannabinoid withdrawal in mice

Although the behavioral effects of acute and chronic exposure to cannabinoids have been extensively studied in mice, spontaneous withdrawal following exposure to cannabinoids has not been well characterized in this species. To address this issue, different groups of mice were treated for 5 days with saline, 20-36 mg/kg/day of the CB partial agonist Δ9-tetrahydrocannabinol (Δ9-THC), or 0.06-0.1 mg/kg/day of the CB high-efficacy agonist AM2389. Initial studies assessed changes in observable behavior (paw tremors) that were scored from the recordings taken at 4 or 24 h after the last injection. Subsequently, radiotelemetry was used to continuously measure body temperature and locomotor activity before (baseline), during, and after the 5-day dosing regimens. Results show that increases in paw tremors occurred following 5-day exposure to AM2389 or Δ9-THC. In telemetry studies, acute AM2389 or THC decreased both temperature and activity. Rapid tolerance occurred to the hypothermic effects of the cannabinoids, whereas locomotor activity continued to be suppressed following each drug injection. In contrast, increases in locomotor activity were evident 12-72 h after discontinuing daily injections of either 0.06 or 0.1 mg/kg/day AM2389. Increases in locomotor activity were also noted in mice treated daily with 30 or 36, but not 20 mg/kg/day Δ9-THC; these effects were smaller and appeared later than effects seen in AM2389-treated mice. These results indicate that the discontinuation of daily treatment with a CB high-efficacy agonist will yield evidence of spontaneous withdrawal that may reflect prior dependence, and that the degree of cannabinoid dependence may vary in relation to the dose or efficacy of the agonist injected daily.

MD Simulations Revealing Special Activation Mechanism of Cannabinoid Receptor 1

Cannabinoid receptor 1 (CB1) is a G protein-coupled receptor (GPCR) that is gaining much interest for its regulating role in the central nervous system and its value as a drug target. Structures of CB1 in inactive and active states have revealed conformational change details that are not common in other GPCRs. Here, we performed molecular dynamics simulations of CB1 in different ligand binding states and with mutations to reveal its activation mechanism. The conformational change of the “twin toggle switch” residues F200^3.36 and W356^6.48 that correlates with ligand efficacy is identified as a key barrier step in CB1 activation. Similar conformational change of residues 3.36/6.48 is also observed in melanocortin receptor 4, showing this “twin toggle switch” residue pair is crucial for the activation of multiple GPCR members.

Age-related changes in CB1 receptor expression and function and the behavioral effects of cannabinoid receptor ligands

Cannabinoid use has increased among aging individuals. However, little information on age-related differences in the behavioral effects of these agents is available. To explore potential differences in the behavioral effects of cannabinoids, we determined effects of Δ⁹-tetrahydrocannabinol (THC, 1-10 mg/kg) or rimonabant (0.3-3.2 mg/kg) on operant fixed-ratio responding (FR10) for food in young adult (6 months) and aged (29 months) rats. THC dose-dependently decreased responding for food. Rimonabant alone had little or no effect on responding up to 1.0 mg/kg, but disrupted responding following a 3.2 mg/kg dose. Rimonabant (1.0 mg/kg) partially antagonized response disruption by THC. These effects were similar in young adult and aged rats. However, aging has been reported to change the neurobiology of cannabinoid CB1 receptors. To confirm our rats exhibited such differences, we assessed CB1 receptor binding sites and function in six subcortical (caudate, nucleus accumbens CA1, and CA2/CA3), and three cortical regions (medial prefrontal, temporal, entorhinal) in young adult (6 months) or aged (26 months) male Lewis rats using quantitative autoradiography. CB1 receptor binding sites were reduced in cortical, but not subcortical brain regions of aged rats. CB1 receptor function, at the level of receptor-G protein interaction, was not different in any region studied. Results indicate that down-regulation of CB1 receptor binding sites observed in cortical regions of aged rats was not accompanied by a commensurate decrease in CB1 receptor-stimulated [³⁵S]GTPγS binding, suggesting a compensatory increase in receptor function in cortical areas. Together, our results provide additional evidence of age-related changes in central CB1 receptor populations. However, the functional compensation for decreased CB1 receptor binding may mitigate changes in behavioral effects of cannabinoids. With the rising use of cannabinoid-based therapeutics among aging populations, further evaluation of age-related changes in the cannabinoid system and the impact of these changes on effects of this class of drugs is warranted.

Effects of cannabinoid exposure on short-term memory and medial orbitofrontal cortex function and chemistry in adolescent female rhesus macaques

Aim

There is increasing concern that cannabinoid exposure during adolescence may disturb brain maturation and produce long-term cognitive deficits. However, studies in human subjects have provided limited evidence for such causality. The present study utilized behavioral and neuroimaging endpoints in female non-human primates to examine the effects of acute and chronic exposure during adolescence to the cannabinoid receptor full agonist, AM2389, on cognitive processing and brain function and chemistry.

Materials and methods

Adolescent female rhesus macaques were trained on a titrating-delay matching-to-sample (TDMTS) touchscreen task that assays working memory. TDMTS performance was assessed before and during chronic exposure to AM2389, following antagonist (rimonabant) administration, and after discontinuation of the chronic regimen. Resting-state fMRI connectivity and magnetic resonance spectroscopy data were acquired prior to drug treatment, during chronic exposure, and following its discontinuation. Voxels were placed in the medial orbitofrontal cortex (mOFC), a region involved in memory processing that undergoes maturation during adolescence.

Results

TDMTS performance was dose-dependently disrupted by acute AM2389; however, chronic treatment resulted in tolerance to these effects. TDMTS performance also was disrupted by discontinuation of the chronic regimen but surprisingly, not by rimonabant administration during chronic AM2389 treatment. mOFC N-acetylaspartate/creatine ratio decreased after acute and chronic administration but returned to baseline values following discontinuation of chronic treatment. Finally, intra-network functional connectivity (mOFC) increased during the chronic regimen and returned to baseline values following its discontinuation.

Conclusion

Neural effects of a cannabinergic drug may persist during chronic exposure, notwithstanding the development of tolerance to behavioral effects. However, such effects dissipate upon discontinuation, reflecting the restorative capacity of affected brain processes.

UK Medical Cannabis registry: an analysis of clinical outcomes of medicinal cannabis therapy for chronic pain conditions

OBJECTIVES

To explore pain-specific, general health-related quality of life (HRQoL), and safety outcomes of chronic pain patients prescribed cannabis-based medicinal products (CBMPs).

METHODS

A case series was performed using patients with chronic pain from the UK Medical Cannabis Registry. Primary outcomes were changes in Brief Pain Inventory short-form (BPI), Short-form McGill Pain Questionnaire-2 (SF-MPQ-2), Visual Analogue Scale-Pain (VAS), General Anxiety Disorder-7 (GAD-7), Sleep Quality Scale (SQS), and EQ-5D-5L, at 1, 3, and 6 months from baseline. Statistical significance was defined at p-value<0.050.

RESULTS

190 patients were included. Median initial Δ⁹-tetrahydrocannabinol and cannabidiol daily doses were 2.0mg (range:0.0-442.0mg) and 20.0mg (range:0.0-188.0mg) respectively. Significant improvements were observed within BPI, SF-MPQ-2, GAD-7, SQS, EQ-5D-5 L index, and VAS measures at all timepoints (p<0.050). Seventy-five adverse events (39.47%) were reported, of which 37 (19.47%) were rated as mild, 23 (12.11%) as moderate, and 14 (7.37%) as severe. Nausea (n=11; 5.8%) was the most frequent adverse event.

CONCLUSION

An association was identified between patients with chronic pain prescribed CBMPs and improvements in pain-specific and general HRQoL outcomes. Most adverse events were mild to moderate in severity, indicating CBMPs were well tolerated. Inherent limitations of study design limit its overall applicability.

Aberrant inhibitory processing in the somatosensory cortices of cannabis-users

BACKGROUND

Delta-9 tetrahydrocannabinol (THC) is a major exogenous psychoactive agent, which acts as a partial agonist on cannabinoid (CB₁) receptors. THC is known to inhibit presynaptic neurotransmission and has been repeatedly linked to acute decrements in cognitive function across multiple domains. Previous electrophysiological studies of sensory gating have shown specific deficits in inhibitory processing in cannabis-users, but to date these findings have been limited to the auditory cortices, and the degree to which these aberrations extend to other brain regions remains largely unknown.

METHODS

We used magnetoencephalography (MEG) and a paired-pulse somatosensory stimulation paradigm to probe inhibitory processing in 29 cannabis-users (i.e. at least four times per month) and 41 demographically matched non-user controls. MEG responses to each stimulation were imaged in both the oscillatory and time domain, and voxel time-series data were extracted to quantify the dynamics of sensory gating, oscillatory gamma activity, evoked responses, and spontaneous neural activity.

RESULTS

We observed robust somatosensory responses following both stimulations, which were used to compute sensory gating ratios. Cannabis-users exhibited significantly impaired gating relative to non-users in somatosensory cortices, as well as decreased spontaneous neural activity. In contrast, oscillatory gamma activity did not appear to be affected by cannabis use.

CONCLUSIONS

We observed impaired gating of redundant somatosensory information and altered spontaneous activity in the same cortical tissue in cannabis-users compared to non-users. These data suggest that cannabis use is associated with a decline in the brain's ability to properly filter repetitive information and impairments in cortical inhibitory processing.

Pharmacological and Toxicological Effects of Phytocannabinoids and Recreational Synthetic Cannabinoids: Increasing Risk of Public Health

Synthetic Cannabinoids (CBs) are a novel class of psychoactive substances that have rapidly evolved around the world with the addition of diverse structural modifications to existing molecules which produce new structural analogues that can be associated with serious adverse health effects. Synthetic CBs represent the largest class of drugs detected by the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) with a total of 207 substances identified from 2008 to October 2020, and 9 compounds being reported for the first time. Synthetic CBs are sprayed on natural harmless herbs with an aim to mimic the euphoric effect of Cannabis. They are sold under different brand names including Black mamba, spice, K2, Bombay Blue, etc. As these synthetic CBs act as full agonists at the CB receptors, they are much more potent than natural Cannabis and have been increasingly associated with acute to chronic intoxications and death. Due to their potential toxicity and abuse, the US government has listed some synthetic CBs under schedule 1 classification. The present review aims to provide a focused overview of the literature concerning the development of synthetic CBs, their abuse, and potential toxicological effects including renal toxicity, respiratory depression, hyperemesis syndrome, cardiovascular effects, and a range of effects on brain function.

Clinical Outcome Data of First Cohort of Chronic Pain Patients Treated With Cannabis-Based Sublingual Oils in the United Kingdom: Analysis From the UK Medical Cannabis Registry

Cannabis-based medicinal products (CBMPs) are an emerging therapeutic option in the management of primary chronic pain, using the role of the endocannabinoid system in modulating central and peripheral pain processes. Despite promising preclinical data, there is a paucity of high-quality evidence to support the use of CBMPs for chronic pain. This study aimed to investigate the health-related quality-of-life outcomes of patients with chronic pain who were prescribed CBMP oil preparations (Adven, Curaleaf International, Guernsey, UK). This study is a case series of patients from the UK Medical Cannabis Registry, who were treated with CBMP oils for an indication of chronic pain. The primary outcomes were the changes in Brief Pain Inventory short form, Short-Form McGill Pain Questionnaire-2, Visual Analog Scale Pain, General Anxiety Disorder-7, Sleep Quality Scale, and EQ-5D-5L, at 1, 3, and 6 months. One hundred ten patients were included. Significant improvements in Sleep Quality Scale, EQ-5D-5L pain and discomfort subscale, and Brief Pain Inventory Interference Subscale (P < .05) at 1, 3, and 6 months were demonstrated. There were no notable differences between cannabis-naïve and previous cannabis users in quality-of-life outcomes. The adverse event incidence was 30.0%, with most (n = 58; 92.1%) adverse events being mild or moderate in intensity. Treatment of chronic pain with Adven CBMP oils was associated with an improvement in pain-specific outcomes, health-related quality of life, and self-reported sleep quality. Relative safety was demonstrated over medium-term prescribed use. While these findings must be treated with caution considering the limitations of study design, they can inform future clinical trials.

Resting state functional connectivity in adolescent synthetic cannabinoid users with and without attention-deficit/hyperactivity disorder

OBJECTIVE

Synthetic cannabinoids (SCs) have become increasingly popular in recent years, especially among adolescents. The first aim of the current study was to examine resting-state functional connectivity (rsFC) in SC users compared to controls. Our second aim was to examine the influence of comorbid attention-deficit/hyperactivity disorder (ADHD) symptomatology on rsFC changes in SC users compared to controls.

METHODS

Resting-state functional magnetic resonance imaging (fMRI) analysis included 25 SC users (14 without ADHD and 11 with ADHD combined type) and 12 control subjects.

RESULTS

We found (i) higher rsFC between the default mode network (DMN) and salience network, dorsal attention network and cingulo-opercular network, and (ii) lower rsFC within the DMN and between the DMN and visual network in SC users compared to controls. There were no significant differences between SC users with ADHD and controls, nor were there any significant differences between SC users with and without ADHD.

CONCLUSIONS

We found the first evidence of abnormalities within and between resting state networks in adolescent SC users without ADHD. In contrast, SC users with ADHD showed no differences compared to controls. These results suggest that comorbidity of ADHD and substance dependence may show different rsFC alterations than substance use alone.

Glucocorticoids, Stress and Delta-9 Tetrahydrocannabinol (THC) during Early Embryonic Development

Elevated molecular stress in women is known to have negative impacts on the reproductive development of oocytes and the embryos prior to implantation. In recent years, the prevalence of cannabis use among women of reproductive age has risen due to its ability to relieve psychological stress and nausea, which are mediated by its psychoactive component, ∆-9-tetrahydrocannabinol (THC). Although cannabis is the most popular recreational drug of the 21st century, much is unknown about its influence on molecular stress in reproductive tissues. The current literature has demonstrated that THC causes dose- and time-dependent alterations in glucocorticoid signaling, which have the potential to compromise morphology, development, and quality of oocytes and embryos. However, there are inconsistencies across studies regarding the mechanisms for THC-dependent changes in stress hormones and how either compounds may drive or arrest development. Factors such as variability between animal models, physiologically relevant doses, and undiscovered downstream gene targets of both glucocorticoids and THC could account for such inconsistencies. This review evaluates the results of studies which have investigated the effects of glucocorticoids on reproductive development and how THC may alter stress signaling in relevant tissues.

Effects of Cannabis Consumption on Sleep

Despite the fact that medical properties of Cannabis have been recognized for more than 5000 years, the use of Cannabis for medical purposes have recently reemerged and became more accessible. Cannabis is usually employed as a self-medication for the treatment of insomnia disorder. However, the effects of Cannabis on sleep depend on multiple factors such as metabolomic composition of the plant, dosage and route of administration. In the present chapter, we reviewed the main effect Cannabis on sleep. We focused on the effect of "crude or whole plant" Cannabis consumption (i.e., smoked, oral or vaporized) both in humans and experimental animal models.The data reviewed establish that Cannabis modifies sleep. Furthermore, a recent experimental study in animals suggests that vaporization (which is a recommended route for medical purposes) of Cannabis with high THC and negligible CBD, promotes NREM sleep. However, it is imperative to perform new clinical studies in order to confirm if the administration of Cannabis could be a beneficial therapy for the treatment of sleep disorders.

Cannabis Phytochemicals: A Review of Phytocannabinoid Chemistry and Bioactivity as Neuroprotective Agents

With the advent of medical cannabis usage globally, there has been a renewed interest in exploring the chemical diversity of this unique plant. Cannabis produces hundreds of unique phytocannabinoids, which not only have diverse chemical structures but also a range of cellular and molecular actions, interesting pharmacological properties, and biological actions. In addition, it produces other flavonoids, stilbenoids, and terpenes that have been variably described as conferring additional or so-called entourage effects to whole-plant extracts when used in therapeutic settings. This review explores this phytochemical diversity in relation to specific bioactivity ascribed to phytocannabinoids as neuroprotective agents. It outlines emergent evidence for the potential for selected phytocannabinoids and other cannabis phytochemicals to mitigate factors such as inflammation and oxidative stress as drivers of neurotoxicity, in addition to focusing on specific interactions with pathological misfolding proteins, such as amyloid β, associated with major forms of neurodegenerative diseases such as Alzheimer’s disease.

Cannabis Use and Internalizing/Externalizing Symptoms in Youth: A Canadian Population-Based Study

PURPOSE

With the recent legalization of cannabis for nonmedicinal purposes in Canada, it is becoming increasingly important to understand the potential mental health risks that cannabis may present. The objective of this study was to estimate associations between the frequency of cannabis use and the presence of elevated internalizing (e.g., anxiety and depression) and externalizing (e.g., conduct disorder and attention deficit hyperactivity disorder) symptoms within Ontario youth aged 12-17 years.

METHODS

The 2014 Ontario Child Health Study included Emotional and Behavioural Scales used to assess internalizing and externalizing symptoms. To assess associations between internalizing/externalizing symptoms and cannabis use, the Ontario Child Health Study-Emotional and Behavioural Scales were dichotomized using the upper quintile (those with the most severe symptoms). Logistic regression was used to estimate odds ratios (ORs) to quantify the association between the frequency of cannabis use and the presence of elevated internalizing and externalizing symptoms. Estimates used a recommended procedure (replicate bootstrap weighting) to address design effects.

RESULTS

A significant association between frequent cannabis use and elevated externalizing symptoms was observed with an OR of 2.17 (1.80-2.62) in males and 5.13 (4.24-6.21) in females. Similar significant associations were also observed between frequent cannabis use and elevated internalizing symptoms with an OR of 2.07 (1.74-2.47) in males and an OR of 3.40 (2.73-4.24) in females. These associations were still present after adjusting for age, binge drinking, smoking, and negative/positive parenting.

CONCLUSIONS

Cannabis use, especially in females and frequent users, is associated with elevated levels of internalizing and externalizing symptoms.

Incident testicular cancer in relation to using marijuana and smoking tobacco: A systematic review and meta-analysis of epidemiologic studies

BACKGROUND

Recent epidemiologic studies identified credible associations between marijuana smoking and risk of nonseminomatous testicular germ cell tumors (TGCTs), but did not distinguish exposure to cannabinoid compounds from exposure to other constituents of smoke.

METHODS

We implemented a systematic review of scholarly literature followed by random effects meta-analysis to quantitatively synthesize published data relating incident TGCT to each of 2 exposure histories: ever using marijuana, and ever smoking tobacco.

RESULTS

We identified four epidemiologic studies of marijuana use and 12 of tobacco smoking. Summary data concur with earlier reports of a specific association of marijuana use with nonseminoma, summary odds ratio [sOR] = 1.71 (95% confidence interval [CI] 1.12-2.60), and identify a positive association, sOR = 1.18 (95% CI 1.05-1.33), between tobacco smoking and all TGCT.

CONCLUSIONS

Available data accord with positive associations between incident TGCT and each exposure, implicating both cannabinoid compounds and other constituents of smoke. Etiologic interpretation awaits epidemiologic studies that assess associations between tobacco smoking and nonseminomatous TGCT, investigating not only these exposures but also both co-use of tobacco and marijuana and smoke-free sources of cannabinoids, while adequately evaluating potential confounding among all of these exposures.

Prediction of the Binding Affinities and Selectivity for CB1 and CB2 Ligands Using Homology Modeling, Molecular Docking, Molecular Dynamics Simulations, and MM-PBSA Binding Free Energy Calculations

Cannabinoids are a group of chemical compounds that have been used for thousands of years due to their psychoactive function and systemic physiological effects. There are at least two types of cannabinoid receptors, CB1 and CB2, which belong to the G protein-coupled receptor superfamily and can trigger different signaling pathways to exert their physiological functions. In this study, several representative agonists and antagonists of both CB1 and CB2 were systematically studied to predict their binding affinities and selectivity against both cannabinoid receptors using a set of hierarchical molecular modeling and simulation techniques, including homology modeling, molecular docking, molecular dynamics (MD) simulations and end point binding free energy calculations using the molecular mechanics/Poisson-Boltzmann surface area-WSAS (MM-PBSA-WSAS) method, and molecular mechanics/generalized Born surface area (MM-GBSA) free energy decomposition. Encouragingly, the calculated binding free energies correlated very well with the experimental values and the correlation coefficient square (R²), 0.60, was much higher than that of an efficient but less accurate docking scoring function (R² = 0.37). The hotspot residues for CB1 and CB2 in both active and inactive conformations were identified via MM-GBSA free energy decomposition analysis. The comparisons of binding free energies, ligand-receptor interaction patterns, and hotspot residues among the four systems, namely, agonist-bound CB1, agonist-bound CB2, antagonist-bound CB1, and antagonist-bound CB2, enabled us to investigate and identify distinct binding features of these four systems, with which one can rationally design potent, selective, and function-specific modulators for the cannabinoid receptors.

Different receptor mechanisms underlying phytocannabinoid- versus synthetic cannabinoid-induced tetrad effects: Opposite roles of CB1 /CB2 versus GPR55 receptors

BACKGROUND AND PURPOSE

Cannabis or cannabinoids produce characteristic tetrad effects-analgesia, hypothermia, catalepsy and suppressed locomotion, which are believed to be mediated by the activation of cannabinoid CB₁ receptors. Given recent findings of CB₂ and GPR55 receptors in the brain, we examined whether these receptors are also involved in cannabinoid action.

EXPERIMENTAL APPROACH

We compared Δ⁹ -tetrahydrocannabinol (Δ⁹ -THC)-, WIN55212-2-, or XLR11-induced tetrad effects between wild-type (WT) and each genotype of CB₁ -, CB₂ - or GPR55-knockout (KO) mice and then observed the effects of antagonists of these receptors on these tetrad effects in WT mice.

KEY RESULTS

Systemic administration of Δ⁹ -THC, WIN55212-2 or XLR11 produced dose-dependent tetrad effects in WT mice. Genetic deletion or pharmacological blockade of CB₁ receptors abolished the tetrad effects produced by all three cannabinoids. Unexpectedly, genetic deletion of CB₂ receptor abolished analgesia and catalepsy produced by Δ⁹ -THC or WIN55212-2, but not by XLR11. Microinjections of Δ⁹ -THC into the lateral ventricles also produced tetrad effects in WT, but not in CB₁ -KO mice. CB₂ -KO mice displayed a reduction in intraventricular Δ⁹ -THC-induced analgesia and catalepsy. In contrast to CB₁ and CB₂ receptors, genetic deletion of GPR55 receptors caused enhanced responses to Δ⁹ -THC or WIN55212-2. Antagonisim of CB₁ , CB₂ or GPR55 receptors produced alterations similar to those observed in each genotype mouse line.

CONCLUSIONS AND IMPLICATIONS

These findings suggest that in addition to CB₁ , both CB₂ and GPR55 receptors are also involved in some pharmacological effects produced by cannabinoids. CB₁ /CB₂ , in contrast to GPR55, receptors appears to play opposite roles in cannabinoid action.

Interaction of Cannabis Use and Aging: From Molecule to Mind

Given the aging Baby Boomer generation, changes in cannabis legislation, and the growing acknowledgment of cannabis for its therapeutic potential, it is predicted that cannabis use in the older population will escalate. It is, therefore, important to determine the interaction between the effects of cannabis and aging. The aim of this report is to describe the link between cannabis use and the aging brain. Our review of the literature found few and inconsistent empirical studies that directly address the impact of cannabis use on the aging brain. However, research focused on long-term cannabis use points toward cumulative effects on multimodal systems in the brain that are similarly affected during aging. Specifically, the effects of cannabis and aging converge on overlapping networks in the endocannabinoid, opioid, and dopamine systems that may affect functional decline particularly in the hippocampus and prefrontal cortex, which are critical areas for memory and executive functioning. To conclude, despite the limited current knowledge on the potential interactive effects between cannabis and aging, evidence from the literature suggests that cannabis and aging effects are concurrently present across several neurotransmitter systems. There is a great need for future research to directly test the interactions between cannabis and aging.

The effects of delta-9-tetrahydrocannabinol on Krüppel-like factor-4 expression, redox homeostasis, and inflammation in the kidney of diabetic rat

Diabetes mellitus is a complex, multifactorial disorder that is attributed to pancreatic β cell dysfunction. Pancreatic β cell dysfunction results in declining utilization of glucose by peripheral tissues as kidney and it leads to nephropathy. Excessive production and accumulation of free radicals and incapable antioxidant defense system lead to impaired redox status. Macromolecular damage may occur due to impaired redox status and also immune imbalance. Δ9-Tetrahydrocannabinol (THC) is the main active ingredient in cannabis. THC acts as an immunomodulator and an antioxidant agent. Our aim was to evaluate the effects of THC in the diabetic kidney. We analyzed macromolecular damage biomarkers as protein carbonyl (PCO), lipid hydroperoxide (LHP), malondialdehyde (MDA), 8-hydroxy-2'-deoxyguanosine (8-OHdG), and antioxidant defense system biomarkers as thiol fractions (T-SH, NP-SH, P-SH) and Cu/Zn-superoxide dismutase activity for the antioxidative effects of THC. Furthermore, mRNA expression of Krüppel-like factor-4, secreted immunopositive cell number changes of interleukin-6, nuclear factor κβ (NF-κβ), and peroxisome proliferator-activated receptor-γ and tumor necrosis factor α (TNF-α) levels were analyzed for the immunomodulatory activity of THC. Diabetic rats showed significantly increased levels of PCO, LHP, MDA, and 8-OHdG when compared with controls (P < 0.05 for each parameter). THC significantly reduced the elevated levels of PCO and 8-OHdG (P < 0.05 for both parameters) and also LHP and MDA levels were insignificantly reduced by THC. Also, thiol fractions insignificantly increased in THC administered diabetic kidney when compared with diabetic rats. The NF-κβ cell number significantly decreased in the diabetic rats treated with THC compared with the diabetic group. According to our data, THC has ameliorative effects on the impaired redox status of diabetic kidney and also it acts as an immunomodulator. Therefore, THC might be used as a therapeutic agent for diabetic kidneys but its usage in the healthy kidney may show adverse effects.

Cannabinoid CB1 and CB2 receptor mechanisms underlie cannabis reward and aversion in rats

BACKGROUND AND PURPOSE

Endocannabinoids are critically involved in brain reward functions, mediated by activation of CB₁ receptors, reflecting their high density in the brain. However, the recent discovery of CB₂ receptors in the brain, particularly in the midbrain dopamine neurons, has challenged this view and inspired us to re-examine the roles of both CB₁ and CB₂ receptors in the effects of cannabis.

EXPERIMENTAL APPROACH

In the present study, we used the electrical intracranial self-stimulation paradigm to evaluate the effects of various cannabinoid drugs on brain reward in laboratory rats and the roles of CB₁ and CB₂ receptors activation in brain reward function(s).

KEY RESULTS

Two mixed CB₁ / CB₂ receptor agonists, Δ⁹ -tetrahydrocannabinol (Δ⁹ -THC) and WIN55,212-2, produced biphasic effects-mild enhancement of brain-stimulation reward (BSR) at low doses but inhibition at higher doses. Pretreatment with a CB₁ receptor antagonist (AM251) attenuated the low dose-enhanced BSR, while a CB₂ receptor antagonist (AM630) attenuated high dose-inhibited BSR. To confirm these opposing effects, rats were treated with selective CB₁ and CB₂ receptor agonists. These compounds produced significant BSR enhancement and inhibition, respectively.

CONCLUSIONS AND IMPLICATIONS

CB₁ receptor activation produced reinforcing effects, whereas CB₂ receptor activation was aversive. The subjective effects of cannabis depend on the balance of these opposing effects. These findings not only explain previous conflicting results in animal models of addiction but also explain why cannabis can be either rewarding or aversive in humans, as expression of CB₁ and CB₂ receptors may differ in the brains of different subjects.

The neuropsychopharmacology of cannabis: A review of human imaging studies

The laws governing cannabis are evolving worldwide and associated with changing patterns of use. The main psychoactive drug in cannabis is Δ⁹-tetrahydrocannabinol (THC), a partial agonist at the endocannabinoid CB₁ receptor. Acutely, cannabis and THC produce a range of effects on several neurocognitive and pharmacological systems. These include effects on executive, emotional, reward and memory processing via direct interactions with the endocannabinoid system and indirect effects on the glutamatergic, GABAergic and dopaminergic systems. Cannabidiol, a non-intoxicating cannabinoid found in some forms of cannabis, may offset some of these acute effects. Heavy repeated cannabis use, particularly during adolescence, has been associated with adverse effects on these systems, which increase the risk of mental illnesses including addiction and psychosis. Here, we provide a comprehensive state of the art review on the acute and chronic neuropsychopharmacology of cannabis by synthesizing the available neuroimaging research in humans. We describe the effects of drug exposure during development, implications for understanding psychosis and cannabis use disorder, and methodological considerations. Greater understanding of the precise mechanisms underlying the effects of cannabis may also give rise to new treatment targets.

Oximes short-acting CB1 receptor agonists

New oximes short-acting CB1 agonists were explored by the introduction of an internal oxime and polar groups at the C3 alkyl tail of Δ⁸-THC. The scope of the research was to drastically alter two important physicochemical properties hydrophobicity (log P) and topological surface area (tPSA) of the compound, which play a critical role in tissue distribution and sequestration (depot effect). Key synthesized analogs demonstrated sub-nanomolar affinity for CB1, marked reduction in hydrophobicity (ClogP∼2.5-3.5 vs 9.09 of Δ⁸-THC-DMH), and found to function as either agonists (trans-oximes) or neutral antagonists (cis-oximes) in a cAMP functional assay. All oxime analogs showed comparable affinity at the CB2 receptor, but surprisingly they were found to function as inverse agonists for CB2. In behavioral studies (i.e. analgesia, hypothermia) trans-oxime 8a exhibited a predictable fast onset (∼20 min) and short duration of pharmacological action (∼180 min), in contrast to the very prolonged duration of Δ⁸-THC-DMH (>24 h), thus limiting the potential for severe psychotropic side-effects associated with persistent activation of the CB1 receptor. We have conducted 100 ns molecular dynamic (MD) simulations of CB1 complexes with AM11542 (CB1 agonist) and both trans-8a and cis-8b isomeric oximes. These studies revealed that the C3 alkyl tail of cis-8b orientated within the CB1 binding pocket in a manner that triggered a conformational change that stabilized the CB1 receptor at its inactive-state (antagonistic functional effect). In contrast, the trans-8a isomer's conformation was coincided with that of the AM11542 CB1 agonist-bound structure, stabilizing the CB1 receptor at the active-state (agonistic functional effect). We have selected oxime trans-8a based on its potency for CB1, and favorable pharmacodynamic profile, such as fast onset and predictable duration of pharmacological action, for evaluation in pre-clinical models of anorexia nervosa.

Phytocannabinoids modulate emotional memory processing through interactions with the ventral hippocampus and mesolimbic dopamine system: implications for neuropsychiatric pathology

Growing clinical and preclinical evidence suggests a potential role for the phytocannabinoid cannabidiol (CBD) as a pharmacotherapy for various neuropsychiatric disorders. In contrast, delta-9-tetrahydrocannabinol (THC), the primary psychoactive component in cannabis, is associated with acute and neurodevelopmental propsychotic side effects through its interaction with central cannabinoid type 1 receptors (CB1Rs). CB1R stimulation in the ventral hippocampus (VHipp) potentiates affective memory formation through inputs to the mesolimbic dopamine (DA) system, thereby altering emotional salience attribution. These changes in DA activity and salience attribution, evoked by dysfunctional VHipp regulatory actions and THC exposure, could predispose susceptible individuals to psychotic symptoms. Although THC can accelerate the onset of schizophrenia, CBD displays antipsychotic properties, can prevent the acquisition of emotionally irrelevant memories, and reverses amphetamine-induced neuronal sensitization through selective phosphorylation of the mechanistic target of rapamycin (mTOR) molecular signaling pathway. This review summarizes clinical and preclinical evidence demonstrating that distinct phytocannabinoids act within the VHipp and associated corticolimbic structures to modulate emotional memory processing through changes in mesolimbic DA activity states, salience attribution, and signal transduction pathways associated with schizophrenia-related pathology.

Long-Lasting In Vivo Effects of the Cannabinoid CB1 Antagonist AM6538

AM6538 is a cannabinoid antagonist that binds CB1 receptors expressed in HEK-293 cells in a wash-resistant manner. The effects of AM6538 in live animals has not previously been established. We characterized the antagonist effects of AM6538 in male mice, using a warm-water tail-withdrawal assay, and in male squirrel monkeys trained to discriminate the CB1 agonist AM4054 from vehicle. The cannabinoid agonists WIN 55,212, Δ⁹-tetrahydrocannabinol (THC), and AM4054 all produced 100% maximum possible antinociceptive effects in mice following vehicle pretreatment. One-hour pretreatment with increasing doses of AM6538 (0.1-10 mg/kg) produced first rightward, then downward shifts of the agonist dose-effect functions. Rimonabant, 1-10 mg/kg, produced parallel rightward shifts of the AM4054 dose-effect functions, and baseline effects of AM4054 were nearly recovered within 24 hours following 10 mg/kg of rimonabant. In contrast, in mice treated with 10 mg/kg of AM6538, antagonism of THC or AM4054 lasted up to 7 days. AM6538 also antagonized the discriminative stimulus effects of AM4054 in squirrel monkeys in a dose-related manner, and the effects of 3.2 mg/kg of AM6538 endured for more than 7 days. The effective reduction in CB1 receptor reserve was used to calculate the relative efficacy (tau values) of WIN 55,212, THC, and AM4054 in mice and of AM4054 monkeys, with results indicating that THC has a lower efficacy than WIN 55,212 or AM4054 in mice. These results demonstrate that AM6538 is a long-acting CB antagonist in vivo, and further suggest that differences in CB efficacy can be revealed in behavioral assays following AM6538 treatment.

Current evidence of cannabinoid-based analgesia obtained in preclinical and human experimental settings

Cannabinoids have a long record of recreational and medical use and become increasingly approved for pain therapy. This development is based on preclinical and human experimental research summarized in this review. Cannabinoid CB₁ receptors are widely expressed throughout the nociceptive system. Their activation by endogenous or exogenous cannabinoids modulates the release of neurotransmitters. This is reflected in antinociceptive effects of cannabinoids in preclinical models of inflammatory, cancer and neuropathic pain, and by nociceptive hypersensitivity of cannabinoid receptor-deficient mice. Cannabis-based medications available for humans mainly comprise Δ⁹ -tetrahydrocannabinol (THC), cannabidiol (CBD) and nabilone. During the last 10 years, six controlled studies assessing analgesic effects of cannabinoid-based drugs in human experimental settings were reported. An effect on nociceptive processing could be translated to the human setting in functional magnetic resonance imaging studies that pointed at a reduced connectivity within the pain matrix of the brain. However, cannabinoid-based drugs heterogeneously influenced the perception of experimentally induced pain including a reduction in only the affective but not the sensory perception of pain, only moderate analgesic effects, or occasional hyperalgesic effects. This extends to the clinical setting. While controlled studies showed a lack of robust analgesic effects, cannabis was nearly always associated with analgesia in open-label or retrospective reports, possibly indicating an effect on well-being or mood, rather than on sensory pain. Thus, while preclinical evidence supports cannabinoid-based analgesics, human evidence presently provides only reluctant support for a broad clinical use of cannabinoid-based medications in pain therapy.

SIGNIFICANCE

Cannabinoids consistently produced antinociceptive effects in preclinical models, whereas they heterogeneously influenced the perception of experimentally induced pain in humans and did not provide robust clinical analgesia, which jeopardizes the translation of preclinical research on cannabinoid-mediated antinociception into the human setting.

Molecular Pharmacology of Phytocannabinoids

Cannabis sativa has been used for recreational, therapeutic and other uses for thousands of years. The plant contains more than 120 C₂₁ terpenophenolic constituents named phytocannabinoids. The Δ⁹-tetrahydrocannabinol type class of phytocannabinoids comprises the largest proportion of the phytocannabinoid content. Δ⁹-tetrahydrocannabinol was first discovered in 1971. This led to the discovery of the endocannabinoid system in mammals, including the cannabinoid receptors CB₁ and CB₂. Δ⁹-Tetrahydrocannabinol exerts its well-known psychotropic effects through the CB₁ receptor but this effect of Δ⁹-tetrahydrocannabinol has limited the use of cannabis medicinally, despite the therapeutic benefits of this phytocannabinoid. This has driven research into other targets outside the endocannabinoid system and has also driven research into the other non-psychotropic phytocannabinoids present in cannabis. This chapter presents an overview of the molecular pharmacology of the seven most thoroughly investigated phytocannabinoids, namely Δ⁹-tetrahydrocannabinol, Δ⁹-tetrahydrocannabivarin, cannabinol, cannabidiol, cannabidivarin, cannabigerol, and cannabichromene. The targets of these phytocannabinoids are defined both within the endocannabinoid system and beyond. The pharmacological effect of each individual phytocannabinoid is important in the overall therapeutic and recreational effect of cannabis and slight structural differences can elicit diverse and competing physiological effects. The proportion of each phytocannabinoid can be influenced by various factors such as growing conditions and extraction methods. It is therefore important to investigate the pharmacology of these seven phytocannabinoids further, and characterise the large number of other phytocannabinoids in order to better understand their contributions to the therapeutic and recreational effects claimed for the whole cannabis plant and its extracts.

Analysis of natural product regulation of cannabinoid receptors in the treatment of human disease

The organized, tightly regulated signaling relays engaged by the cannabinoid receptors (CBs) and their ligands, G proteins and other effectors, together constitute the endocannabinoid system (ECS). This system governs many biological functions including cell proliferation, regulation of ion transport and neuronal messaging. This review will firstly examine the physiology of the ECS, briefly discussing some anomalies in the relay of the ECS signaling as these are consequently linked to maladies of global concern including neurological disorders, cardiovascular disease and cancer. While endogenous ligands are crucial for dispatching messages through the ECS, there are also commonalities in binding affinities with copious exogenous ligands, both natural and synthetic. Therefore, this review provides a comparative analysis of both types of exogenous ligands with emphasis on natural products given their putative safer efficacy and the role of Δ9-tetrahydrocannabinol (Δ9-THC) in uncovering the ECS. Efficacy is congruent to both types of compounds but noteworthy is the effect of a combination therapy to achieve efficacy without unideal side-effects. An example is Sativex that displayed promise in treating Huntington's disease (HD) in preclinical models allowing for its transition to current clinical investigation. Despite the in vitro and preclinical efficacy of Δ9-THC to treat neurodegenerative ailments, its psychotropic effects limit its clinical applicability to treating feeding disorders. We therefore propose further investigation of other compounds and their combinations such as the triterpene, α,β-amyrin that exhibited greater binding affinity to CB₁ than CB₂ and was more potent than Δ9-THC and the N-alkylamides that exhibited CB₂ selective affinity; the latter can be explored towards peripherally exclusive ECS modulation. The synthetic CB₁ antagonist, Rimonabant was pulled from commercial markets for the treatment of diabetes, however its analogue SR144528 maybe an ideal lead molecule towards this end and HU-210 and Org27569 are also promising synthetic small molecules.

Behavioral Determinants of Cannabinoid Self-Administration in Old World Monkeys

Reinforcing effects of Δ⁹-tetrahydrocannabinol (THC), the primary active ingredient in marijuana, as assessed with self-administration (SA), has only been established in New World primates (squirrel monkeys). The objective of this study was to investigate some experimental factors that may enhance intravenous SA of THC and the cannabinoid receptor (CBR) agonist CP 55 940 in Old World monkeys (rhesus and cynomolgus), a species that has been used extensively in biomedical research. In one experiment, male rhesus monkeys (N=9) were trained to respond under a fixed-ratio 10 schedule of food presentation. The effects of CP 55 940 (1.0-10 μg/kg, i.v.) and THC (3.0-300 μg/kg, i.v.) on food-maintained responding and body temperature were determined in these subjects prior to giving them access to self-administer each drug. Both drugs dose-dependently decreased food-maintained responding. CP 55 940 (0.001-3.0 μg/kg) functioned as a reinforcer in three monkeys, whereas THC (0.01-10 μg/kg) did not have reinforcing effects in any subject. CP 55 940 was least potent to decrease food-maintained responding in the monkeys in which CP 55 940 functioned as a reinforcer. Next, THC was administered daily to monkeys until tolerance developed to rate-decreasing effects. When THC SA was reexamined, it functioned as a reinforcer in three monkeys. In a group of cocaine-experienced male cynomolgus monkeys (N=4), THC SA was examined under a second-order schedule of reinforcement; THC functioned as reinforcer in two monkeys. These data suggest that SA of CBR agonists may be relatively independent of their rate-decreasing effects in Old World monkeys. Understanding individual differences in vulnerability to THC SA may lead to novel treatment strategies for marijuana abuse.

Synthetic Pot: Not Your Grandfather's Marijuana

In the early 2000s in Europe and shortly thereafter in the USA, it was reported that 'legal' forms of marijuana were being sold under the name K2 and/or Spice. Active ingredients in K2/Spice products were determined to be synthetic cannabinoids (SCBs), producing psychotropic actions via CB1 cannabinoid receptors, similar to those of Δ9-tetrahydrocannabinol (Δ9-THC), the primary active constituent in marijuana. Often abused by adolescents and military personnel to elude detection in drug tests due to their lack of structural similarity to Δ9-THC, SCBs are falsely marketed as safe marijuana substitutes. Instead, SCBs are a highly structural diverse group of compounds, easily synthesized, which produce very dangerous adverse effects occurring by, as of yet, unknown mechanisms. Therefore, available evidence indicates that K2/Spice products are clearly not safe marijuana alternatives.

Salience attribution and its relationship to cannabis-induced psychotic symptoms

BACKGROUND

Cannabis is a widely used drug associated with increased risk for psychosis. The dopamine hypothesis of psychosis postulates that altered salience processing leads to psychosis. We therefore tested the hypothesis that cannabis users exhibit aberrant salience and explored the relationship between aberrant salience and dopamine synthesis capacity.

METHOD

We tested 17 cannabis users and 17 age- and sex-matched non-user controls using the Salience Attribution Test, a probabilistic reward-learning task. Within users, cannabis-induced psychotic symptoms were measured with the Psychotomimetic States Inventory. Dopamine synthesis capacity, indexed as the influx rate constant K i cer , was measured in 10 users and six controls with 3,4-dihydroxy-6-[18F]fluoro-l-phenylalanine positron emission tomography.

RESULTS

There was no significant difference in aberrant salience between the groups [F 1,32 = 1.12, p = 0.30 (implicit); F 1,32 = 1.09, p = 0.30 (explicit)]. Within users there was a significant positive relationship between cannabis-induced psychotic symptom severity and explicit aberrant salience scores (r = 0.61, p = 0.04) and there was a significant association between cannabis dependency/abuse status and high implicit aberrant salience scores (F 1,15 = 5.8, p = 0.03). Within controls, implicit aberrant salience was inversely correlated with whole striatal dopamine synthesis capacity (r = -0.91, p = 0.01), whereas this relationship was non-significant within users (difference between correlations: Z = -2.05, p = 0.04).

CONCLUSIONS

Aberrant salience is positively associated with cannabis-induced psychotic symptom severity, but is not seen in cannabis users overall. This is consistent with the hypothesis that the link between cannabis use and psychosis involves alterations in salience processing. Longitudinal studies are needed to determine whether these cognitive abnormalities are pre-existing or caused by long-term cannabis use.

Behavioral Characterization of κ Opioid Receptor Agonist Spiradoline and Cannabinoid Receptor Agonist CP55940 Mixtures in Rats

Pain is a significant clinical problem, and there is a need for more effective treatments with reduced adverse effects that currently limit the use of μ opioid receptor agonists. Synthetic κ opioid receptor agonists have no abuse liability and well-documented antinociceptive effects; however, adverse effects (diuresis, dysphoria) preclude their use in the clinic. Combining κ opioids with nonopioid drugs (cannabinoid receptor agonists) allows for smaller doses of each drug to produce antinociception. This study tested whether a potentially useful effect of the κ opioid receptor agonist 2-(3,4-dichlorophenyl)-N-methyl-N-[(5R,7S,8S)-7-pyrrolidin-1-yl-1-oxaspiro[4.5]decan-8-yl] (spiradoline; antinociception) is selectively enhanced by the cannabinoid receptor agonist 2-[(1R,2R,5R)-5-hydroxy-2-(3-hydroxypropyl) cyclohexyl]-5-(2-methyloctan-2-yl)phenol (CP55940). Cumulative dose-response functions were determined in eight male Sprague-Dawley rats for spiradoline (0.032-32.0 mg/kg, i.p.) and CP55940 (0.0032-1.0 mg/kg, i.p.) for antinociception, hypothermia, food-maintained responding, and diuresis. Alone, each drug dose dependently increased tail withdrawal latencies from 50°C water, decreased body temperature by ∼4°C, and eliminated food-maintained responding. Spiradoline, but not CP55940, significantly increased urine output at doses that eliminated responding. Smaller doses of spiradoline and CP55940 in mixtures (3:1, 1:1, and 1:3 spiradoline:CP55940) had effects comparable to those observed with larger doses of either drug administered alone: the interaction was additive for antinociception and additive or greater than additive for hypothermia and food-maintained responding. Collectively, these data fail to provide support for the use of these mixtures for treating acute pain; however, κ opioid/cannabinoid mixtures might be useful for treating pain under other conditions (e.g., chronic pain), but only if the adverse effects of both drugs are not enhanced in mixtures.