Enantiomeric cannabinoids: stereospecificity of psychotropic activity

An emerging trend in Novel Psychoactive Substances (NPSs): designer THC

Since its discovery as one of the main components of cannabis and its affinity towards the cannabinoid receptor CB1, serving as a means to exert its psychoactivity, Δ9-tetrahydrocannabinol (Δ9-THC) has inspired medicinal chemists throughout history to create more potent derivatives. Initially, the goal was to synthesize chemical probes for investigating the molecular mechanisms behind the pharmacology of Δ9-THC and finding potential medical applications. The unintended consequence of this noble intent has been the proliferation of these compounds for recreational use. This review comprehensively covers the most exhaustive number of THC-like cannabinoids circulating on the recreational market. It provides information on the chemistry, synthesis, pharmacology, analytical assessment, and experiences related to the psychoactive effects reported by recreational users on online forums. Some of these compounds can be found in natural cannabis, albeit in trace amounts, while others are entirely artificial. Moreover, to circumvent legal issues, many manufacturers resort to semi-synthetic processes starting from legal products extracted from hemp, such as cannabidiol (CBD). Despite the aim to encompass all known THC-like molecules, new species emerge on the drug users' pipeline each month. Beyond posing a significantly high public health risk due to unpredictable and unknown side effects, scientific research consistently lags behind the rapidly evolving recreational market.

An overview on synthetic and biological activities of cannabidiol (CBD) and its derivatives

(-)-Cannabidiol is a class of non-psychoactive plant cannabinoids derived from cannabis plants. Currently, Epidiolex (Cannabidiol) has been approved by the FDA for the treatment of two rare and severe forms of epilepsy related diseases, namely Lennox-Gastaut syndrome (LGS) and Dravet (DS). In addition, Cannabidiol and its structural analogues have received increasing attention due to their potential therapeutic effects such as neuroprotection, anti-epilepsy, anti-inflammation, anti-anxiety, and anti-cancer. Based on literature review, no comprehensive reviews on the synthesis of Cannabidiol and its derivatives have been found in recent years. Therefore, this article summarizes the published synthesis methods of Cannabidiol and the synthesis routes of Cannabidiol derivatives, and introduces the biological activities of some Cannabidiol analogues that have been studied extensively and have significant activities.

Ambient ionization mass spectrometry applied to new psychoactive substance analysis

In the past decade a plethora of drugs with similar effects to controlled psychoactive drugs, like cannabis, amfetamine (amphetamine), or lysergic acid diethylamide, have been synthesized. These drugs can collectively be classified under the term new psychoactive substances (NPS) and are used for recreational purposes. The novelty of the substances, alongside the rapid rate of emergence and structural variability, makes their detection as well as their legal control highly challenging, increasing the demand for rapid and easy-to-use analytical techniques for their detection and identification. Therefore, interest in ambient ionization mass spectrometry applied to NPS has grown in recent years, which is largely because it is relatively fast and simple to use and has a low operating cost. This review aims to provide a critique of the suitability of current ambient ionization techniques for the analysis of NPS in the forensic and clinical toxicology fields. Consideration is given to analytical performance and ease of implementation, including ionization efficiency, selectivity, sensitivity, quantification, analyte chemistry, molecular coverage, validation, and practicality.

Unexpected improvement of hyperhidrosis with cannabidiol

Hyperhidrosis is characterized by excessive sweating and it affects almost 5% of the population. The affected age group is wide, and it can affect from children to elderlies. There are two types of hyperhidrosis: generalized and focal. Treatment depends on the symptoms presented. In more severe cases, radiofrequency sympatholysis and bilateral thoracic sympathectomy are the options. However, recurrence is possible or the postoperative appearance of conditions called compensatory hyperhidrosis or reflex hyperhidrosis. We describe two cases of patients treated with Cannabidiol who had significant and unexpected improvement of hyperhidrosis. The first patient received Cannabidiol specific for public presentations at work, and the second patient had a diagnosis of autism spectrum disorder. The hyperhidrosis improved in both patients immediately after using Cannabidiol.

Major Phytocannabinoids and Their Related Compounds: Should We Only Search for Drugs That Act on Cannabinoid Receptors?

The most important discoveries in pharmacology, such as certain classes of analgesics or chemotherapeutics, started from natural extracts which have been found to have effects in traditional medicine. Cannabis, traditionally used in Asia for the treatment of pain, nausea, spasms, sleep, depression, and low appetite, is still a good candidate for the development of new compounds. If initially all attention was directed to the endocannabinoid system, recent studies suggest that many of the clinically proven effects are based on an intrinsic chain of mechanisms that do not necessarily involve only cannabinoid receptors. Recent research has shown that major phytocannabinoids and their derivatives also interact with non-cannabinoid receptors such as vanilloid receptor 1, transient receptor ankyrin 1 potential, peroxisome proliferator-activated receptor-gamma or glitazone receptor, G55 protein-coupled receptor, and nuclear receptor, producing pharmacological effects in diseases such as Alzheimer's, epilepsy, depression, neuropathic pain, cancer, and diabetes. Nonetheless, further studies are needed to elucidate the precise mechanisms of these compounds. Structure modulation of phytocannabinoids, in order to improve pharmacological effects, should not be limited to the exploration of cannabinoid receptors, and it should target other courses of action discovered through recent research.

The synthetic CB1 cannabinoid receptor selective agonists: Putative medical uses and their legalization

More than 500 molecules have been identified as components of Cannabis sativa (C. sativa), of which the most studied is Δ⁹-tetrahydrocannabinol (Δ⁹-THC). Several studies have suggested that Δ⁹-THC exerts diverse biological effects, ranging from fragmentation of DNA to behavioral disruptions. Currently, it is accepted that most of the pharmacological properties of Δ⁹-THC engage the activation of the cannabinoid receptors, named CB₁ and CB₂. Interestingly, multiple pieces of evidence have suggested that the cannabinoid receptors play an active role in the modulation of several diseases leading to the design of synthetic cannabinoid-like compounds. Advances in the development of synthetic CB₁ cannabinoid receptor selective agonists as therapeutical approaches are, however, limited. This review focuses on available evidence searched in PubMed regarding the synthetic CB₁ cannabinoid receptor selective agonists such as AM-1235, arachidonyl-2' chloroethylamide (ACEA), CP 50,556-1 (Levonantradol), CP-55,940, HU-210, JWH-007, JWH-018, JWH-200 (WIN 55,225), methanandamide, nabilone, O-1812, UR-144, WIN 55,212-2, nabiximols, and dronabinol. Indeed, it would be ambitious to describe all available evidence related to the synthetic CB₁ cannabinoid receptor selective agonists. However, and despite the positive evidence on the positive results of using these compounds in experimental models of health disturbances and preclinical trials, we discuss evidence in regards some concerns due to side effects.

Serotonin 2A receptors and cannabinoids

Accumulating evidence has proven that both exogenous cannabinoids as well as imbalances in the endocannabinoid system are involved in the onset and development of mental disorders such as anxiety, depression, or schizophrenia. Extensive recent research in this topic has mainly focused on the molecular mechanisms by which cannabinoid agonists may contribute to the pathophysiology of these disorders. Initially, serotonin neurotransmitter garnered most attention due to its relationship to mood disorders and mental diseases, with little attention to specific receptors. To date, the focus has redirected toward the understanding of different serotonin receptors, through a demonstration of its versatile pharmacology and synergy with different modulators. Serotonin 2A receptors are a good example of this phenomenon, and the complex signaling that they trigger appears of high relevance in the context of mental disorders, especially in schizophrenia. This chapter will analyze most relevant attributes of serotonin 2A receptors and the endocannabinoid system, and will highlight the evidence toward the functional bidirectional interaction between these elements in the brain as well as the impact of the endocannabinoid system dysregulation on serotonin 2A receptors functionality.

The neuropharmacology of cannabinoid receptor ligands in central signaling pathways

The endocannabinoid system is a complex neuronal system involved in a number of biological functions, like attention, anxiety, mood, memory, appetite, reward, and immune responses. It is at the centre of scientific interest, which is driven by therapeutic promise of certain cannabinoid ligands and the changing legalization of herbal cannabis in many countries. The endocannabinoid system is a modulatory system, with endocannabinoids as retrograde neurotransmitters rather than direct neurotransmitters. Neuropharmacology of cannabinoid ligands in the brain can therefore be understood in terms of their modulatory actions through other neurotransmitter systems. The CB₁ receptor is chiefly responsible for effects of endocannabinoids and analogous ligands in the brain. An overview of the neuropharmacology of several cannabinoid receptor ligands, including endocannabinoids, herbal cannabis and synthetic cannabinoid receptor ligands is given in this review. Their mechanism of action at the endocannabinoid system is described, mainly in the brain. In addition, effects of cannabinoid ligands on other neurotransmitter systems will also be described, such as dopamine, serotonin, glutamate, noradrenaline, opioid, and GABA. In light of this, therapeutic potential and adverse effects of cannabinoid receptor ligands will also be discussed.

Biased agonism at the cannabinoid receptors - Evidence from synthetic cannabinoid receptor agonists

The type 1 and type 2 cannabinoid receptors are G protein-coupled receptors implicated in a variety of physiological processes and diseases. Synthetic cannabinoid receptor agonists (SCRAs) were originally developed to explore the therapeutic benefits of cannabinoid receptor activation, although more recently, these compounds have been diverted to the recreational drug market and are increasingly associated with incidences of toxicity. A prominent concept in contemporary pharmacology is functional selectivity or biased agonism, which describes the ability of ligands to elicit differential activation of signalling pathways through stabilisation of distinct receptor conformations. Biased agonists may maximise drug effectiveness by reducing on-target adverse effects if they are mediated by signalling pathways distinct from those that drive the therapeutic effects. For the cannabinoid receptors, it remains unclear as to which signalling pathways mediate desirable and adverse effects. However, given their structural diversity and potential to induce a plethora of signalling effects, SCRAs provide the most promising prospect for detecting and studying bias at the cannabinoid receptors. This review summarises the emerging evidence of SCRA bias at the cannabinoid receptors.

[Clinical variants of psychoses in patients using synthetic cannabinoids (Spice)]

OBJECTIVE

To describe the structure of psychoses developed due to synthetic cannabinoids (Spice).

MATERIAL AND METHODS

Forty-six men, aged 18-35 years, with psychosis during abstinence were studied and followed up for 2 years.

RESULTS AND CONCLUSION

Four clinical variants with predominant delirious symptoms (27%) or hallucinatory symptoms (19%) or affective-delusions (21%) or mental automatisms (33%) were identified. The follow-up revealed the manifestations of schizophrenic process in 17% of the patients. Clinical and differential diagnostic characteristics of these variants in synthetic cannabinoids users are described.

Current advances in Vibrio harveyi quorum sensing as drug discovery targets

Vibrio harveyi is a marine bacterial pathogen which infects a wide range of marine organisms and results in severe loss. Antibiotics have been used for prophylaxis and treatment of V. harveyi infection. However, antibiotic resistance is a major public health threat to both human and animals. Therefore, there is an urgent need for novel antimicrobial agents with new modes of action. In V. harveyi, many virulence factors production and bioluminescence formation depend on its quorum sensing (QS) network. Therefore, the QS system has been widely investigated as an effective potential target for the treatment of V. harveyi infection. This perspective focuses on the quorum sensing inhibitors (QSIs) of V. harveyi QS systems (LuxM/N, LuxS/PQ, and CqsA/S) and evaluates medicinal chemistry strategies.

Cannabinoids, Chemical Senses, and Regulation of Feeding Behavior

The herb Cannabis sativa has been traditionally used in many cultures and all over the world for thousands of years as medicine and recreation. However, because it was brought to the Western world in the late 19th century, its use has been a source of controversy with respect to its physiological effects as well as the generation of specific behaviors. In this regard, the CB1 receptor represents the most relevant target molecule of cannabinoid components on nervous system and whole-body energy homeostasis. Thus, the promotion of CB1 signaling can increase appetite and stimulate feeding, whereas blockade of CB1 suppresses hunger and induces hypophagia. Taste and flavor are sensory experiences involving the oral perception of food-derived chemicals and drive a primal sense of acceptable or unacceptable for what is sampled. Therefore, research within the last decades focused on deciphering the effect of cannabinoids on the chemical senses involved in food perception and consequently in the pattern of feeding. In this review, we summarize the data on the effect of cannabinoids on chemical senses and their influences on food intake control and feeding behavior.

Efficacy of Cannabinoids in a Pre-Clinical Drug-Screening Platform for Alzheimer's Disease

Finding a therapy for Alzheimer's disease (AD) is perhaps the greatest challenge for modern medicine. The chemical scaffolds of many drugs in the clinic today are based upon natural products from plants, yet Cannabis has not been extensively examined as a source of potential AD drug candidates. Here, we determine if a number of non-psychoactive cannabinoids are neuroprotective in a novel pre-clinical AD and neurodegeneration drug-screening platform that is based upon toxicities associated with the aging brain. This drug discovery paradigm has yielded several compounds in or approaching clinical trials for AD. Eleven cannabinoids were assayed for neuroprotection in assays that recapitulate proteotoxicity, loss of trophic support, oxidative stress, energy loss, and inflammation. These compounds were also assayed for their ability to remove intraneuronal amyloid and subjected to a structure-activity relationship analysis. Pairwise combinations were assayed for their ability to synergize to produce neuroprotective effects that were greater than additive. Nine of the 11 cannabinoids have the ability to protect cells in four distinct phenotypic neurodegeneration screening assays, including those using neurons that lack CB1 and CB2 receptors. They are able to remove intraneuronal Aβ, reduce oxidative damage, and protect from the loss of energy or trophic support. Structure-activity relationship (SAR) data show that functional antioxidant groups such as aromatic hydroxyls are necessary but not sufficient for neuroprotection. Therefore, there is a need to focus upon CB1 agonists that have these functionalities if neuroprotection is the goal. Pairwise combinations of THC and CBN lead to a synergistic neuroprotective interaction. Together, these results significantly extend the published data by showing that non-psychoactive cannabinoids are potential lead drug candidates for AD and other neurodegenerative diseases.

Psychotic Disorders in Patients Who Use Synthetic Cannabinoids

OBJECTIVE

The main objective of this study was to investigate the structure of psychotic disorders due to synthetic cannabinoid use and to determine differences in clinical characteristics and disease course between such substance-induced psychosis and psychosis associated with a primary diagnosis of schizophrenia.

METHODS

This was a longitudinal, observational cohort study that included male patients who underwent inpatient treatment in the intensive care unit or in the emergency department due to substance-induced psychoses. The follow-up period was up to 2 years.

RESULTS

We identified 4 clinical variants of substance-induced psychoses in patients who use synthetic cannabinoids.

CONCLUSIONS

Our study revealed that psychotic symptoms are typical manifestations in association with intoxication with synthetic cannabinoids, and we identified several nonspecific characteristics of the psychoses that may occur in patients intoxicated with synthetic cannabinoids. We also identified a number of signs that may indicate the presence of substance-induced psychoses.

Synthetic Strategies for (-)-Cannabidiol and Its Structural Analogs

(-)-Cannabidiol ((-)-CBD), a non-psychoactive phytocannabinoid from Cannabis, and its structural analogs have received growing attention in recent years because of their potential therapeutic benefits, including neuroprotective, anti-epileptic, anti-inflammatory, anxiolytic, and anti-cancer properties. (-)-CBD and its analogs have been obtained mainly based on extraction from the natural source; however, the conventional extraction-based methods have some drawbacks, such as poor quality control along with purification difficulty. Chemical-synthetic strategies for (-)-CBD could tackle these issues, and, additionally, generate novel (-)-CBD analogs that exhibit advanced biological activities. This review concisely summarizes the historic and recent milestones in the synthetic strategies for (-)-CBD and its analogs.

Beyond THC and Endocannabinoids

Research in the cannabinoid field, namely on phytocannabinoids, the endogenous cannabinoids anandamide and 2-arachidonoyl glycerol and their metabolizing and synthetic enzymes, the cannabinoid receptors, and anandamide-like cannabinoid compounds, has expanded tremendously over the last few years. Numerous endocannabinoid-like compounds have been discovered. The Cannabis plant constituent cannabidiol (CBD) was found to exert beneficial effects in many preclinical disease models ranging from epilepsy, cardiovascular disease, inflammation, and autoimmunity to neurodegenerative and kidney diseases and cancer. CBD was recently approved in the United States for the treatment of rare forms of childhood epilepsy. This has triggered the development of many CBD-based products for human use, often with overstated claims regarding their therapeutic effects. In this article, the recently published research on the chemistry and biological effects of plant cannabinoids (specifically CBD), endocannabinoids, certain long-chain fatty acid amides, and the variety of relevant receptors is critically reviewed.

Effects of cannabinoids on the development of chick embryos in ovo

We have examined the effects of the synthetic cannabinoids HU 210 and HU 211, the plant-derived cannabidiol and the endogenous cannabinoid anandamide on the viability and development of chick embryos. Fertilized White Leghorn chicken eggs were injected with the test compounds or carrier vehicle, via a drilled small hole in the egg, directly into the egg yolk. After nine days of exposure, the embryonal viability, length and wet weight of embryos, and wet weight of brains were measured, and the development stages were assessed according to the Hamburger and Hamilton (HH) scale. The potent synthetic cannabinoid receptor agonist HU 210 and the non-psychotropic cannabidiol were embryotoxic at the highest concentrations examined (10 µM and 50 µM, respectively), with no viable embryos after the HU 210 injection, and 20% viability after the cannabidiol injections. The effects of HU 210 on the chick embryo were attenuated by α-tocopherol and the cannabinoid receptor antagonist AM251, whereas only α-tocopherol gave a statistically significant protection against the embryotoxic effects of cannabidiol. This study shows that exposure to plant-derived or synthetic cannabinoids during early embryonal development decreases embryonal viability. Extrapolation of data across species is of course difficult, but the data would argue against the use of cannabinoids, be it recreationally or therapeutically, during pregnancy.

Selective modulation of the cannabinoid type 1 (CB1) receptor as an emerging platform for the treatment of neuropathic pain

Neuropathic pain is caused by a lesion or dysfunction in the nervous system, and it may arise from illness, be drug-induced or caused by toxin exposure. Since the discovery of two G-protein-coupled cannabinoid receptors (CB1 and CB2) nearly three decades ago, there has been a rapid expansion in our understanding of cannabinoid pharmacology. This is currently one of the most active fields of neuropharmacology, and interest has emerged in developing cannabinoids and other small molecule modulators of CB1 and CB2 as therapeutics for neuropathic pain. This short review article provides an overview of the chemotypes currently under investigation for the development of novel neuropathic pain treatments targeting CB1 receptors.

Cannabinoid ligands, receptors and enzymes: Pharmacological tools and therapeutic potential

Endocannabinoids have been identified to have roles in numerous physiological and pathological processes. Largely due to the association of the effects of Cannabis administration on mental states, the CNS impact of the endocannabinoid system has been the most intensively studied. Here, we provide a brief summary of the endocannabinoid system, comprising the receptors and the multiple endogenous lipid derivatives which activate them, as well as the enzymes which control the levels of these lipid derivatives. We identify pharmacological tools which may be used to interrogate the endocannabinoid system, as well as current and future options to exploit the system in the clinic.

The Effects of Cannabinoids on Executive Functions: Evidence from Cannabis and Synthetic Cannabinoids-A Systematic Review

Background—Cannabis is the most popular illicit drug in the Western world. Repeated cannabis use has been associated with short and long-term range of adverse effects. Recently, new types of designer-drugs containing synthetic cannabinoids have been widespread. These synthetic cannabinoid drugs are associated with undesired adverse effects similar to those seen with cannabis use, yet, in more severe and long-lasting forms. Method—A literature search was conducted using electronic bibliographic databases up to 31 December 2017. Specific search strategies were employed using multiple keywords (e.g., “synthetic cannabinoids AND cognition,” “cannabis AND cognition” and “cannabinoids AND cognition”). Results—The search has yielded 160 eligible studies including 37 preclinical studies (5 attention, 25 short-term memory, 7 cognitive flexibility) and 44 human studies (16 attention, 15 working memory, 13 cognitive flexibility). Both pre-clinical and clinical studies demonstrated an association between synthetic cannabinoids and executive-function impairment either after acute or repeated consumptions. These deficits differ in severity depending on several factors including the type of drug, dose of use, quantity, age of onset and duration of use. Conclusions—Understanding the nature of the impaired executive function following consumption of synthetic cannabinoids is crucial in view of the increasing use of these drugs.

Synthesis, radio-synthesis and in vitro evaluation of terminally fluorinated derivatives of HU-210 and HU-211 as novel candidate PET tracers

We report the synthesis of terminally fluorinated HU-210 and HU-211 analogues (HU-210F and HU-211F, respectively) and their biological evaluation as ligands of cannabinoid receptors (CB₁ and CB₂) and N-methyl d-aspartate receptor (NMDAR). [¹⁸F]-labelled HU-210F was radiosynthesised from the bromo-substituted precursor. In vitro assays showed that both HU-210F and HU-211F retain the potent pharmacological profile of HU-210 and HU-211, suggesting that [¹⁸F]-radiolabelled HU-210F and HU-211F could have potential as PET tracers for in vivo imaging.

The Endocannabinoid System and Heart Disease: The Role of Cannabinoid Receptor Type 2

Decades of research has provided evidence for the role of the endocannabinoid system in human health and disease. This versatile system, consisting of two receptors (CB1 and CB2), their endogenous ligands (endocannabinoids), and metabolic enzymes has been implicated in a wide variety of disease states, ranging from neurological disorders to cancer. CB2 has gained much interest for its beneficial immunomodulatory role that can be obtained without eliciting psychotropic effects through CB1. Recent studies have shed light on a protective role of CB2 in cardiovascular disease, an ailment which currently takes more lives each year in Western countries than any other disease or injury. By use of CB2 knockout mice and CB2-selective ligands, knowledge of how CB2 signaling affects atherosclerosis and ischemia has been acquired, providing a major stepping stone between basic science and translational clinical research. Here, we summarize the current understanding of the endocannabinoid system in human pathologies and provide a review of the results from preclinical studies examining its function in cardiovascular disease, with a particular emphasis on possible CB2-targeted therapeutic interventions to alleviate atherosclerosis.

The Chemistry and Pharmacology of Synthetic Cannabinoid Receptor Agonists as New Psychoactive Substances: Origins

Synthetic cannabinoid receptor agonists (SCRAs) have proliferated as new psychoactive substances (NPS) over the past decade. Relative to other classes of NPS, SCRAs are structurally heterogeneous; however, most SCRAs act as potent, high-efficacy agonists of cannabinoid type 1 and type 2 receptors (CB₁ and CB₂, respectively). Characterization of the pharmacology and toxicology of these substances is hindered by the dynamic nature of the SCRA marketplace. Beyond basic pharmacological profiling at CB₁ and CB₂ receptors, very little is known about the acute or chronic effects of SCRAs. Many of the effects of SCRAs are qualitatively similar to those of the Δ⁹-tetrahydrocannabinol (Δ⁹-THC) found in cannabis. However, unlike Δ⁹-THC, SCRAs are frequently associated with serious adverse effects, including cardiotoxicity, nephrotoxicity, and death. This chapter will provide an overview of the structure and function of the primary target for SCRAs, the CB₁ receptor, and survey the structure-activity relationships of the historical SCRAs that served as templates for the earliest generations of NPS.

Crystal structures of agonist-bound human cannabinoid receptor CB1

The cannabinoid receptor 1 (CB1) is the principal target of the psychoactive constituent of marijuana, the partial agonist Δ9-tetrahydrocannabinol (Δ9-THC). Here we report two agonist-bound crystal structures of human CB1 in complex with a tetrahydrocannabinol (AM11542) and a hexahydrocannabinol (AM841) at 2.80 Å and 2.95 Å resolution, respectively. The two CB1-agonist complexes reveal important conformational changes in the overall structure, relative to the antagonist-bound state, including a 53% reduction in the volume of the ligand-binding pocket and an increase in the surface area of the G-protein-binding region. In addition, a 'twin toggle switch' of Phe2003.36 and Trp3566.48 (superscripts denote Ballesteros-Weinstein numbering) is experimentally observed and appears to be essential for receptor activation. The structures reveal important insights into the activation mechanism of CB1 and provide a molecular basis for predicting the binding modes of Δ9-THC, and endogenous and synthetic cannabinoids. The plasticity of the binding pocket of CB1 seems to be a common feature among certain class A G-protein-coupled receptors. These findings should inspire the design of chemically diverse ligands with distinct pharmacological properties.

Cannabinoids in the Cardiovascular System

Cannabinoids are known to modulate cardiovascular functions including heart rate, vascular tone, and blood pressure in humans and animal models. Essential components of the endocannabinoid system, namely, the production, degradation, and signaling pathways of endocannabinoids have been described not only in the central and peripheral nervous system but also in myocardium, vasculature, platelets, and immune cells. The mechanisms of cardiovascular responses to endocannabinoids are often complex and may involve cannabinoid CB₁ and CB₂ receptors or non-CB_1/2 receptor targets. Preclinical and some clinical studies have suggested that targeting the endocannabinoid system can improve cardiovascular functions in a number of pathophysiological conditions, including hypertension, metabolic syndrome, sepsis, and atherosclerosis. In this chapter, we summarize the local and systemic cardiovascular effects of cannabinoids and highlight our current knowledge regarding the therapeutic potential of endocannabinoid signaling and modulation.

An Overview on Medicinal Chemistry of Synthetic and Natural Derivatives of Cannabidiol

Cannabidiol (CBD) has been traditionally used in Cannabis-based preparation, however historically, it has received far less interest as a single drug than the other components of Cannabis. Currently, CBD generates considerable interest due to its beneficial neuroprotective, antiepileptic, anxiolytic, antipsychotic, and anti-inflammatory properties. Therefore, the CBD scaffold becomes of increasing interest for medicinal chemists. This review provides an overview of the chemical structure of natural and synthetic CBD derivatives including the molecular targets associated with these compounds. A clear identification of their biological targets has been shown to be still very challenging.

Cannabinoids and Vanilloids in Schizophrenia: Neurophysiological Evidence and Directions for Basic Research

Much of our knowledge of the endocannabinoid system in schizophrenia comes from behavioral measures in rodents, like prepulse inhibition of the acoustic startle and open-field locomotion, which are commonly used along with neurochemical approaches or drug challenge designs. Such methods continue to map fundamental mechanisms of sensorimotor gating, hyperlocomotion, social interaction, and underlying monoaminergic, glutamatergic, and GABAergic disturbances. These strategies will require, however, a greater use of neurophysiological tools to better inform clinical research. In this sense, electrophysiology and viral vector-based circuit dissection, like optogenetics, can further elucidate how exogenous cannabinoids worsen (e.g., tetrahydrocannabinol, THC) or ameliorate (e.g., cannabidiol, CBD) schizophrenia symptoms, like hallucinations, delusions, and cognitive deficits. Also, recent studies point to a complex endocannabinoid-endovanilloid interplay, including the influence of anandamide (endogenous CB₁ and TRPV₁ agonist) on cognitive variables, such as aversive memory extinction. In fact, growing interest has been devoted to TRPV₁ receptors as promising therapeutic targets. Here, these issues are reviewed with an emphasis on the neurophysiological evidence. First, we contextualize imaging and electrographic findings in humans. Then, we present a comprehensive review on rodent electrophysiology. Finally, we discuss how basic research will benefit from further combining psychopharmacological and neurophysiological tools.

Cannabis Pharmacology: The Usual Suspects and a Few Promising Leads

The golden age of cannabis pharmacology began in the 1960s as Raphael Mechoulam and his colleagues in Israel isolated and synthesized cannabidiol, tetrahydrocannabinol, and other phytocannabinoids. Initially, THC garnered most research interest with sporadic attention to cannabidiol, which has only rekindled in the last 15 years through a demonstration of its remarkably versatile pharmacology and synergy with THC. Gradually a cognizance of the potential of other phytocannabinoids has developed. Contemporaneous assessment of cannabis pharmacology must be even far more inclusive. Medical and recreational consumers alike have long believed in unique attributes of certain cannabis chemovars despite their similarity in cannabinoid profiles. This has focused additional research on the pharmacological contributions of mono- and sesquiterpenoids to the effects of cannabis flower preparations. Investigation reveals these aromatic compounds to contribute modulatory and therapeutic roles in the cannabis entourage far beyond expectations considering their modest concentrations in the plant. Synergistic relationships of the terpenoids to cannabinoids will be highlighted and include many complementary roles to boost therapeutic efficacy in treatment of pain, psychiatric disorders, cancer, and numerous other areas. Additional parts of the cannabis plant provide a wide and distinct variety of other compounds of pharmacological interest, including the triterpenoid friedelin from the roots, canniprene from the fan leaves, cannabisin from seed coats, and cannflavin A from seed sprouts. This chapter will explore the unique attributes of these agents and demonstrate how cannabis may yet fulfil its potential as Mechoulam's professed "pharmacological treasure trove."

From Phytocannabinoids to Cannabinoid Receptors and Endocannabinoids: Pleiotropic Physiological and Pathological Roles Through Complex Pharmacology

Apart from having been used and misused for at least four millennia for, among others, recreational and medicinal purposes, the cannabis plant and its most peculiar chemical components, the plant cannabinoids (phytocannabinoids), have the merit to have led humanity to discover one of the most intriguing and pleiotropic endogenous signaling systems, the endocannabinoid system (ECS). This review article aims to describe and critically discuss, in the most comprehensive possible manner, the multifaceted aspects of 1) the pharmacology and potential impact on mammalian physiology of all major phytocannabinoids, and not only of the most famous one Δ9-tetrahydrocannabinol, and 2) the adaptive pro-homeostatic physiological, or maladaptive pathological, roles of the ECS in mammalian cells, tissues, and organs. In doing so, we have respected the chronological order of the milestones of the millennial route from medicinal/recreational cannabis to the ECS and beyond, as it is now clear that some of the early steps in this long path, which were originally neglected, are becoming important again. The emerging picture is rather complex, but still supports the belief that more important discoveries on human physiology, and new therapies, might come in the future from new knowledge in this field.

Prenatal cannabis exposure - The "first hit" to the endocannabinoid system

As more states and countries legalize medical and/or adult recreational marijuana use, the incidences of prenatal cannabis exposure (PCE) will likely increase. While young people increasingly view marijuana as innocuous, marijuana preparations have been growing in potency in recent years, potentially creating global clinical, public health, and workforce concerns. Unlike fetal alcohol spectrum disorder, there is no phenotypic syndrome associated with PCE. There is also no preponderance of evidence that PCE causes lifelong cognitive, behavioral, or functional abnormalities, and/or susceptibility to subsequent addiction. However, there is compelling circumstantial evidence, based on the principles of teratology and fetal malprogramming, suggesting that pregnant women should refrain from smoking marijuana. The usage of marijuana during pregnancy perturbs the fetal endogenous cannabinoid signaling system (ECSS), which is present and active from the early embryonic stage, modulating neurodevelopment and continuing this role into adulthood. The ECSS is present in virtually every brain structure and organ system, and there is also evidence that this system is important in the regulation of cardiovascular processes. Endocannabinoids (eCBs) undergird a broad spectrum of processes, including the early stages of fetal neurodevelopment and uterine implantation. Delta-9-tetrahydrocannabinol (THC), the psychoactive chemical in cannabis, enters maternal circulation, and readily crosses the placental membrane. THC binds to CB receptors of the fetal ECSS, altering neurodevelopment and possibly rewiring ECSS circuitry. In this review, we discuss the Double-Hit Hypothesis as it relates to PCE. We contend that PCE, similar to a neurodevelopmental teratogen, delivers the first hit to the ECSS, which is compromised in such a way that a second hit (i.e., postnatal stressors) will precipitate the emergence of a specific phenotype. In summary, we conclude that perturbations of the intrauterine milieu via the introduction of exogenous CBs alter the fetal ECSS, predisposing the offspring to abnormalities in cognition and altered emotionality. Based on recent experimental evidence that we will review here, we argue that young women who become pregnant should immediately take a "pregnant pause" from using marijuana.

Cannabinoid Receptors and Their Relationships with Neuropsychiatric Disorders

Cannabinoids are the costituents of the marijuana plants. The central effects of exogenous cannabinoids are implicated in enhancing mood, altering emotional states, and interfering in the formation of short-term memory. Cannabinoid receptors are G protein-coupled receptors with seven transmembrane domains that are expressed on the cell surface with their binding domain exposed to the extracellular space. To date, two cannabinoid receptors have been cloned, CB1 and CB2. Recent evidence suggests that a third ‘CB3’ receptor may be cloned in the near future. The endocannabinoids may represent the first members of a new classes of neuromodulators, that are not stored in cell vesicles, but rather synthesised by the cell on demand. The endogenous cannabinoid system could play a central role in several neuropsychiatric disorders and is also involved in other conditions such as pain, spasticity and neuroprotection. Implication of cannabinoid system in the pathogenesis and development of schizophrenia is also discussed.

Receptome: Interactions between three pain-related receptors or the "Triumvirate" of cannabinoid, opioid and TRPV1 receptors

A growing amount of data demonstrates the interactions between cannabinoid, opioid and the transient receptor potential (TRP) vanilloid type 1 (TRPV1) receptors. These interactions can be bidirectional, inhibitory or excitatory, acute or chronic in their nature, and arise both at the molecular level (structurally and functionally) and in physiological processes, such as pain modulation or perception. The interactions of these three pain-related receptors may also reserve important and new therapeutic applications for the treatment of chronic pain or inflammation. In this review, we summarize the main findings on the interactions between the cannabinoid, opioid and the TRPV1 receptor regarding to pain modulation.

Effect of the synthetic cannabinoid HU-210 on quorum sensing and on the production of quorum sensing-mediated virulence factors by Vibrio harveyi

Background

Bacterial populations communicate through the cell density-dependent mechanism of quorum sensing (QS). Vibrio harveyi, one of the best studied model organisms for QS, was used to explore effects of the synthetic cannabinoid HU-210 on QS and different QS-regulated physiological processes in bacteria.

Results

Analysis of QS-regulated bioluminescence in wild-type and mutant strains of V. harveyi revealed that HU-210 affects the autoinducer-2 (AI-2) pathway, one of three known QS cascades of V. harveyi. Furthermore, QS-mediated biofilm formation and swimming motility in the mutant strain BB152 (AI-1⁻, AI-2⁺) were significantly reduced in the presence of HU-210. HU-210 inhibited QS-mediated virulence factor production without any inhibitory effect on bacterial growth. It also alters the expression of several genes, which are regulated by QS, specifically downregulating the genes of the AI-2 QS cascade.

Conclusion

First evidence is being provided for interference of bacterial signal-transduction systems by a synthetic cannabinoid. The effect of HU-210 was specific to the AI-2 cascade in V. harveyi. AI-2 is known as a "universal autoinducer" and interference with its activity opens a broad spectrum of applications for synthetic cannabinoids in future research as a potential anti-QS agent.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-015-0499-0) contains supplementary material, which is available to authorized users.

Endocannabinoid signaling at the periphery: 50 years after THC

In 1964, the psychoactive ingredient of Cannabis sativa, Δ(9)-tetrahydrocannabinol (THC), was isolated. Nearly 30 years later the endogenous counterparts of THC, collectively termed endocannabinoids (eCBs), were discovered: N-arachidonoylethanolamine (anandamide) (AEA) in 1992 and 2-arachidonoylglycerol (2-AG) in 1995. Since then, considerable research has shed light on the impact of eCBs on human health and disease, identifying an ensemble of proteins that bind, synthesize, and degrade them and that together form the eCB system (ECS). eCBs control basic biological processes including cell choice between survival and death and progenitor/stem cell proliferation and differentiation. Unsurprisingly, in the past two decades eCBs have been recognized as key mediators of several aspects of human pathophysiology and thus have emerged to be among the most widespread and versatile signaling molecules ever discovered. Here some of the pioneers of this research field review the state of the art of critical eCB functions in peripheral organs. Our community effort is aimed at establishing consensus views on the relevance of the peripheral ECS for human health and disease pathogenesis, as well as highlighting emerging challenges and therapeutic hopes.

Early phytocannabinoid chemistry to endocannabinoids and beyond

Isolation and structure elucidation of most of the major cannabinoid constituents--including Δ(9)-tetrahydrocannabinol (Δ(9)-THC), which is the principal psychoactive molecule in Cannabis sativa--was achieved in the 1960s and 1970s. It was followed by the identification of two cannabinoid receptors in the 1980s and the early 1990s and by the identification of the endocannabinoids shortly thereafter. There have since been considerable advances in our understanding of the endocannabinoid system and its function in the brain, which reveal potential therapeutic targets for a wide range of brain disorders.

What we know and do not know about the cannabinoid receptor 2 (CB2)

It has been well appreciated that the endocannabinoid system can regulate immune responses via the cannabinoid receptor 2 (CB2), which is primarily expressed by cells of the hematopoietic system. The endocannabinoid system is composed of receptors, ligands and enzymes controlling the synthesis and degradation of endocannabinoids. Along with endocannabinoids, both plant-derived and synthetic cannabinoids have been shown to bind to and signal through CB2 via G proteins leading to both inhibitory and stimulatory signals depending on the biological process. Because no cannabinoid ligand has been identified that only binds to CB2, the generation of mice deficient in CB2 has greatly expanded our knowledge of how CB2 contributes to immune cell development and function in health and disease. In regards to humans, genetic studies have associated CB2 with a variety of human diseases. Here, we review the endocannabinoid system with an emphasis on CB2 and its role in the immune system.

Neuroprotective effects of the cannabinoid agonist HU210 on retinal degeneration

Cannabinoids have been demonstrated to exert neuroprotective effects on different types of neuronal insults. Here we have addressed the therapeutic potential of the synthetic cannabinoid HU210 on photoreceptor degeneration, synaptic connectivity and functional activity of the retina in the transgenic P23H rat, an animal model for autosomal dominant retinitis pigmentosa (RP). In P23H rats administered with HU210 (100 μg/kg, i.p.) from P24 to P90, ERG recordings showed an amelioration of vision loss, as compared to vehicle-administered animals. Under scotopic conditions, the maximum a-wave amplitudes recorded at P60 and P90 were higher in HU210-treated animals, as compared to the values obtained in untreated animals. The scotopic b-waves were significantly higher in treated animals than in untreated rats at P30, P60 and P90. This attenuation of visual deterioration correlated with a delay in photoreceptor degeneration and the preservation of retinal cytoarchitecture. HU210-treated animals had 40% more photoreceptors than untreated animals. Presynaptic and postsynaptic elements, as well as the synaptic contacts between photoreceptors and bipolar or horizontal cells, were also preserved in HU210-treated P23H rats. These results indicate that HU210 preserves cone and rod structure and function, together with their contacts with postsynaptic neurons, in P23H rats. These data suggest that cannabinoids are potentially useful to delay retinal degeneration in RP patients.

Cannabinoids in disguise: Δ9-tetrahydrocannabinol-like effects of tetramethylcyclopropyl ketone indoles

Synthetic indole-derived cannabinoids have become commonly used recreational drugs and continue to be abused despite their adverse consequences. As compounds that were identified early in the epidemic (e.g., naphthoylindoles) have become legally banned, new compounds have appeared on the drug market. Two tetramethylcyclopropyl ketone indoles, UR-144 [(1-pentyl-1H-indol-3-yl)-(2,2,3,3-tetramethylcyclopropyl)methanone] and XLR-11 [(1-(5-fluoropentyl)-1H-indol-3-yl)-(2,2,3,3-tetramethylcyclopropyl)methanone], recently have been identified in confiscated products. These compounds are structurally related to a series of CB2-selective compounds explored by Abbott Labs. The purpose of the present study was to evaluate the extent to which UR-144 and XLR-11 shared cannabinoid effects with Δ9-tetrahydrocannabinol (Δ9-THC). Indices of in vitro and in vivo activity at cannabinoid receptors were assessed. Similar to other psychoactive cannabinoid agonists, XLR-11 and UR-144 showed low nanomolar (<30) affinity for CB1 and CB2 receptors, activated these receptors as full agonists, and produced dose-dependent effects that were blocked by rimonabant in mice, including antinociception, hypothermia, catalepsy and suppression of locomotor activity. The potency of both compounds was several-fold greater than Δ9-THC. XLR-11 and UR-144 also substituted for Δ9-THC in a Δ9-THC discrimination procedure in mice, effects that were attenuated by rimonabant. Analysis of urine from mice treated with the compounds revealed that both were extensively metabolized, with predominant urinary excretion as glucuronide conjugates. Together, these results demonstrate that UR-144 and XLR-11 share a pharmacological profile of in vitro and in vivo effects with Δ9-THC and other abused indole-derived cannabinoids and would be predicted to produce Δ9-THC-like subjective effects in humans.

The endocannabinoid system and the brain

The psychoactive constituent in cannabis, Δ(9)-tetrahydrocannabinol (THC), was isolated in the mid-1960s, but the cannabinoid receptors, CB1 and CB2, and the major endogenous cannabinoids (anandamide and 2-arachidonoyl glycerol) were identified only 20 to 25 years later. The cannabinoid system affects both central nervous system (CNS) and peripheral processes. In this review, we have tried to summarize research--with an emphasis on recent publications--on the actions of the endocannabinoid system on anxiety, depression, neurogenesis, reward, cognition, learning, and memory. The effects are at times biphasic--lower doses causing effects opposite to those seen at high doses. Recently, numerous endocannabinoid-like compounds have been identified in the brain. Only a few have been investigated for their CNS activity, and future investigations on their action may throw light on a wide spectrum of brain functions.

Synthetic Cannabinoid Use and Sudden Death

Synthetic cannabinoids are chemical compounds that act on the cannabinoid receptors to produce psychoactive effects. Originally created to better understand the cannabinoid receptors, these drugs are readily accessible over the internet or in “head shops” and are sold as herbal incense under various names such as K2, Spice, K9, or Legal Phunk. While neurologic and cardiac toxicity from the use of these compounds has been described, and deaths of individuals that have used synthetic cannabinoids have been publicized in the media, no fatalities directly related to synthetic cannabinoid toxicity have been reported in the scientific literature. This report describes a fatality directly related to the toxic effects of synthetic cannabinoid use. It will also review the development of synthetic cannabinoids, current literature with respect to their toxicity, and the regulatory issues surrounding these substances.

[Isomeric analysis of synthetic cannabinoids detected as designer drugs]

Recently, many psychotropic herbal products, named such as "Spice", were distributed worldwide via the Internet. In our previous study, several synthetic cannabinoids were identified as adulterants in herbal products being available in Japan due to their expected narcotic effects. Among those, two derivatives of Δ(9)-tetrahydrocannabinol (Δ(9)-THC), which is major psychotropic cannabinoid of marijuana, cannabicyclohexanol (CCH, 3-[2-hydroxy-4-(2-methylnonan-2-yl)phenyl]cyclohexan-1-ol) and CP-47,497 (3-[2-hydroxy-4-(2-methyloctan-2-yl)phenyl]cyclohexan-1-ol), have been controlled as designated substances (Shitei-Yakubutsu) under the Pharmaceutical Affairs Law since November 2009. CCH was detected together with its trans-form (1-epimer) in many herbal products, and CCH and CP-47,497 have two chiral centers in the structures. However, the pharmaceutical activities of the isomers of CCH have not been reported. This study presents chiral separations of CCH, its trans-form and CP-47,497 in the products using LC-circular dichroism (CD) and LC-MS analyses. The enantiomeric pairs of CCH, its trans-form and CP-47,497 were separated, respectively. Subsequently, the analyses of the herbal products showed that CCH and its trans-form existed as mixtures of enantiomers and the relative ratios of CCH and the trans-form enantiomers ranged from 42/58% to 53/47% and from 33/67% to 52/48%, respectively.

Is lipid signaling through cannabinoid 2 receptors part of a protective system?

The mammalian body has a highly developed immune system which guards against continuous invading protein attacks and aims at preventing, attenuating or repairing the inflicted damage. It is conceivable that through evolution analogous biological protective systems have been evolved against non-protein attacks. There is emerging evidence that lipid endocannabinoid signaling through cannabinoid 2 (CB₂) receptors may represent an example/part of such a protective system/armamentarium. Inflammation/tissue injury triggers rapid elevations in local endocannabinoid levels, which in turn regulate signaling responses in immune and other cells modulating their critical functions. Changes in endocannabinoid levels and/or CB₂ receptor expressions have been reported in almost all diseases affecting humans, ranging from cardiovascular, gastrointestinal, liver, kidney, neurodegenerative, psychiatric, bone, skin, autoimmune, lung disorders to pain and cancer, and modulating CB₂ receptor activity holds tremendous therapeutic potential in these pathologies. While CB₂ receptor activation in general mediates immunosuppressive effects, which limit inflammation and associated tissue injury in large number of pathological conditions, in some disease states activation of the CB₂ receptor may enhance or even trigger tissue damage, which will also be discussed alongside the protective actions of the CB₂ receptor stimulation with endocannabinoids or synthetic agonists, and the possible biological mechanisms involved in these effects.

Cannabinoid effects on CB1 receptor density in the adolescent brain: an autoradiographic study using the synthetic cannabinoid HU210

The short- and long-term behavioral effects of cannabinoids differ in adolescent and adult rodents. Few studies though have examined the underlying neurochemical changes that occur in the brain following adolescent cannabinoid exposure. In this study, we examined the effect of treatment with the synthetic cannabinoid, HU210, on CB1 receptor density in the brain and on body weight in adolescent male rats. Rats were treated daily with 25, 50, or 100 μg/kg HU210 for 4 or 14 days, or received a single dose of 100 μg/kg HU210 and sacrificed 24 h later. Receptor density was investigated using in vitro autoradiography with the CB1 receptor ligand [(3)H] CP55,940. In contrast to adult animals treated under the same paradigm in a previous study, adolescents continued on average, to gain weight over the course of the study. Weight gain was slowest in the 100 μg/kg group and improved dose dependently with controls gaining the most weight. Following the acute dose of HU210, a trend for a reduction in [(3)H] CP55,940 binding and a significant effect of treatment was observed. Statistically significant, dose-dependent, region-specific decreases in binding were observed in all brain regions examined following 4 and 14 days treatment. The pattern of CB1 receptor downregulation was similar to that observed in adults treated with cannabinoids in previous studies; however, its magnitude was smaller in adolescents. This reduced compensatory response may contribute to some acute behavioral effects, the pharmacological cross-tolerance and the long-lasting, adverse psychological consequences of cannabinoid exposure during adolescence.

Endocannabinoid signaling in neurotoxicity and neuroprotection

The cannabis plant and products produced from it, such as marijuana and hashish, have been used for centuries for their psychoactive properties. The mechanism for how Delta(9)-tetrahydrocannabinol (THC), the active constituent of cannabis, elicits these neurological effects remained elusive until relatively recently, when specific G-protein coupled receptors were discovered that appeared to mediate cellular actions of THC. Shortly after discovery of these specific receptors, endogenous ligands (endocannabinoids) were identified. Since that time, an extensive number of papers have been published on the endocannabinoid signaling system, a widespread neuromodulatory mechanism that influences neurotransmission throughout the nervous system. This paper summarizes presentations given at the 12th International Neurotoxicology Association meeting that described the potential role of endocannabinoids in the expression of neurotoxicity. Dr. Raphael Mechoulam first gave an overview of the discovery of exogenous and endogenous cannabinoids and their potential for neuroprotection in a variety of conditions. Dr. Larry Parsons then described studies suggesting that endocannabinoid signaling may play a selective role in drug reinforcement. Dr. Carey Pope presented information on the role that endocannabinoid signaling may have in the expression of cholinergic toxicity following anticholinesterase exposures. Together, these presentations highlighted the diverse types of neurological insults that may be modulated by endocannabinoids and drugs/toxicants which might influence endocannabinoid signaling pathways.