Functional effects of synthetic cannabinoids versus Δ9 -THC in mice on body temperature, nociceptive threshold, anxiety, cognition, locomotor/exploratory parameters and depression

Differential cannabinoid-like effects and pharmacokinetics of ADB-BICA, ADB-BINACA, ADB-4en-PINACA and MDMB-4en-PINACA in mice: A comparative study

Despite synthetic cannabinoids' (SCs) prevalent use among humans, these substances often lack comprehensive pharmacological data, primarily due to their rapid emergence in the market. This study aimed to discern differences and causal factors among four SCs (ADB-BICA, ADB-BINACA, ADB-4en-PINACA and MDMB-4en-PINACA), with respect to locomotor activity, body temperature and nociception threshold. Adult male C57BL/6 mice received intraperitoneal injections of varying doses (0.5, 0.1 and 0.02 mg/kg) of these compounds. Three substances (including ADB-BINACA, ADB-4en-PINACA and MDMB-4en-PINACA) demonstrated dose- and time-dependent hypolocomotive and hypothermic effects. Notably, 0.1 mg/kg MDMB-4en-PINACA exhibited analgesic properties. However, ADB-BICA did not cause any effects. MDMB-4en-PINACA manifested the most potent and sustained effects, followed by ADB-4en-PINACA, ADB-BINACA and ADB-BICA. Additionally, the cannabinoid receptor 1 (CB1R) antagonist AM251 suppressed the effects induced by acute administration of the substances. Analysis of molecular binding configurations revealed that the four SCs adopted a congruent C-shaped geometry, with shared linker binding pockets conducive to robust steric interaction with CB1R. Essential residues PHE268 , PHE200 and SER173 within CB1R were identified as pivotal contributors to enhancing receptor-ligand associations. During LC-MS/MS analysis, 0.5 mg/kg MDMB-4en-PINACA exhibited the highest plasma concentration and most prolonged detection window post-administration. The study of SCs' pharmacological and pharmacokinetic profiles is crucial for better understanding the main mechanisms of cannabinoid-like effects induced by SCs, interpreting clinical findings related to SC uses and enhancing SCs risk awareness.

FABP5 is important for cognitive function and is an important regulator of the physiological effects and pharmacokinetics of acute Δ9 tetrahydrocannabinol inhalation in mice

Fatty acid binding protein 5 (FABP5) interacts with the endocannabinoid system in the brain via intracellular transport of anandamide, as well as Δ9-tetrahydrocannabinol (THC), the main psychoactive component of cannabis. Previous work has established the behavioral effects of genetic deletion of FABP5, but not in the presence of THC. The present study sought to further elucidate the role of FABP5 on the pharmacokinetic and behavioral response to THC through global deletion. Adult FABP5+/+ and FABP5-/- mice were tested for behavioral response to THC using Open Field (OF), Novel Object Recognition (NOR), T-Maze, Morris Water Maze (MWM), and Elevated Plus Maze (EPM). An additional cohort of mice was used to harvest blood, brains, and liver samples to measure THC and metabolites after acute administration of THC. Behavioral tests showed that some cognitive deficits from FABP5 deletion, particularly in MWM, were blocked by THC administration, while this was not observed in other measures of memory and anxiety (such as T-Maze and EPM). Measurement of THC and metabolites in blood serum and brain tissue through UPLC-MS/MS analysis showed that the pharmacokinetics of THC was altered by FABP5. The present study shows further evidence of the importance of FABP5 in cognitive function. Additionally, results showed that FABP5 is an important regulator of the physiological effects and pharmacokinetics of THC.

Cognitive Alterations in Addictive Disorders: A Translational Approach

The cognitive decline in people with substance use disorders is well known and can be found during both the dependence and drug abstinence phases. At the clinical level, cognitive decline impairs the response to addiction treatment and increases dropout rates. It can be irreversible, even after the end of drug abuse consumption. Improving our understanding of the molecular and cellular alterations associated with cognitive decline could be essential to developing specific therapeutic strategies for its treatment. Developing animal models to simulate drug abuse-induced learning and memory alterations is critical to continue exploring this clinical situation. The main aim of this review is to summarize the most recent evidence on cognitive impairment and the associated biological markers in patients addicted to some of the most consumed drugs of abuse and in animal models simulating this clinical situation. The available information suggests the need to develop more studies to further explore the molecular alterations associated with cognitive impairment, with the ultimate goal of developing new potential therapeutic strategies.

Effects of Δ9-THC and Type-1 Cannabinoid Receptor Agonists in the Elevated Plus Maze Test of Anxiety: A Systematic Review and Meta-Analysis

Δ⁹-THC (the main active compound from Cannabis sativa) and related cannabinoids have been used as drugs of abuse and as medications. They induce a complex set of emotional responses in humans and experimental animals, consisting of either anxiolysis or heightened anxiety. These discrepant effects pose a major challenge for data reproducibility and for developing new cannabinoid-based medicines. In this study, we review and analyze previous data on cannabinoids and anxiety-like behavior in experimental animals. Systematic review and meta-analysis on the effects of type-1 cannabinoid receptor agonists (full or partial, selective or not) in rodents exposed to the elevated plus maze, a widely used test of anxiety-like behavior. Cannabinoids tend to reduce anxiety-like behavior if administered at low doses. THC effects are moderated by the dose factor, with anxiolytic- and anxiogenic-like effects occurring at low-dose (0.075-1 mg/kg) and high-dose (1-10 mg/kg) ranges, respectively. However, some studies report no effect at all regardless of the dose tested. Finally, motor impairment represents a potential confounding factor when high doses are administered. The present analysis may contribute to elucidate the experimental factors underlying cannabinoid effects on anxiety-like behavior and facilitate data reproducibility in future studies.

The effects of preventative cannabidiol in a male neuregulin 1 mouse model of schizophrenia

Cannabidiol (CBD) is a non-intoxicating cannabinoid with antipsychotic-like properties, however it’s potential to prevent schizophrenia development has not been thoroughly investigated. Brain maturation during adolescence creates a window where CBD could potentially limit the development of schizophrenia. The neuregulin 1 transmembrane domain heterozygous (Nrg1 TM HET) mutant mouse shows face, predictive, and construct validity for schizophrenia. Here we sought to determine if CBD given in adolescence could prevent the development of the schizophrenia-relevant phenotype, as well as susceptibility to the psychoactive cannabinoid Δ⁹-tetrahydrocannabinol (THC) in Nrg1 TM HET mice. Adolescent male Nrg1 mutants and wild type-like (WT) animals were administered 30 mg/kg CBD i.p. daily for seven weeks, and were tested for locomotion, social behavior, sensorimotor gating and cognition, and sensitivity to acute THC-induced behaviors. GAD67, GluA1, and NMDAR1 protein levels were measured in the hippocampus, striatum, and prefrontal cortex. Chronic adolescent CBD increased locomotion in animals regardless of genotype, was anxiolytic, and increased social behavior when animals were tested for their acute THC response. CBD did not alleviate the schizophrenia-relevant hyperlocomotive phenotype of Nrg1 mutants, nor deficits in social behaviors. Nrg1 mutant mice treated with CBD and THC showed no habituation to a startle pulse, suggesting CBD increased vulnerability to the startle habituation-reducing effects of THC in mutant mice. CBD increased levels of GluA1, but reduced levels of GAD67 in the hippocampus of Nrg1 mutants. These results suggest adolescent CBD is not effective as a preventative of schizophrenia-relevant behavioral deficits in mutants and may actually contribute to pathological changes in the brain that increase sensitivity to THC in particular behavioral domains.

In Vivo Bio-Activation of JWH-175 to JWH-018: Pharmacodynamic and Pharmacokinetic Studies in Mice

3-(1-Naphthalenylmethyl)-1-pentyl-1H-indole (JWH-175) is a synthetic cannabinoid illegally marketed for its psychoactive cannabis-like effects. This study aimed to investigate and compare in vitro and in vivo pharmacodynamic activity of JWH-175 with that of 1-naphthalenyl (1-pentyl-1H-indol-3-yl)-methanone (JWH-018), as well as evaluate the in vitro (human liver microsomes) and in vivo (urine and plasma of CD-1 male mice) metabolic profile of JWH-175. In vitro binding studies showed that JWH-175 is a cannabinoid receptor agonist less potent than JWH-018 on mouse and human CB1 and CB2 receptors. In agreement with in vitro data, JWH-175 reduced the fESPS in brain hippocampal slices of mice less effectively than JWH-018. Similarly, in vivo behavioral studies showed that JWH-175 impaired sensorimotor responses, reduced breath rate and motor activity, and increased pain threshold to mechanical stimuli less potently than JWH-018. Metabolic studies demonstrated that JWH-175 is rapidly bioactivated to JWH-018 in mice blood, suggesting that in vivo effects of JWH-175 are also due to JWH-018 formation. The pharmaco-toxicological profile of JWH-175 was characterized for the first time, proving its in vivo bio-activation to the more potent agonist JWH-018. Thus, it highlighted the great importance of investigating the in vivo metabolism of synthetic cannabinoids for both clinical toxicology and forensic purposes.

Defining Steric Requirements at CB1 and CB2 Cannabinoid Receptors Using Synthetic Cannabinoid Receptor Agonists 5F-AB-PINACA, 5F-ADB-PINACA, PX-1, PX-2, NNL-1, and Their Analogues

Synthetic cannabinoid receptor agonists (SCRAs) are a diverse class of new psychoactive substances (NPS). They commonly comprise N-alkylated indole, indazole, or 7-azaindole scaffolds with amide-linked pendant amino acid groups. To explore the contribution of the amino acid side chain to the cannabinoid pharmacology of SCRA NPS, a systematic library of side chain-modified SCRAs was prepared based on the recent detections of amino acid derivatives 17 (5F-AB-PINACA), 18 (5F-ADB-PINACA), 15 (PX-1), 19 (PX-2), and 20 (NNL-1). In vitro binding affinities and functional activities at cannabinoid type 1 and 2 receptors (CB₁ and CB₂, respectively) were determined for all the library members using radioligand competition experiments and a fluorescence-based membrane potential assay. Binding affinities and functional activities varied widely across compounds (K_i = 0.32 to >10 000 nM, EC₅₀ = 0.24-1259 nM), with several clear structure-activity relationships (SARs) emerging. Affinity and potency at CB₁ changed as a function of the heterocyclic core (indazole > indole > 7-azaindole) and the pendant amino acid side chain (tert-butyl > iso-propyl > iso-butyl > benzyl > ethyl > methyl > hydrogen). Ensemble docking at CB₁ revealed a clear steric basis for observed SAR trends. Interestingly, although 15 (PX-1) and 19 (PX-2) have been detected in recreational drug markets, they failed to induce centrally CB₁-mediated effects (e.g., hypothermia) in mice using radiobiotelemetry. Together, these data provide insights regarding structural contributions to the cannabimimetic profiles of 17 (5F-AB-PINACA), 18 (5F-ADB-PINACA), 15 (PX-1), 19 (PX-2), 20 (NNL-1), and other SCRA NPS.

Effects of synthetic cannabinoids on psychomotor, sensory and cognitive functions relevant for safe driving

Recreational use of Synthetic Cannabinoids (SCs), one of the largest groups of New Psychoactive Substances (NPS), has increased globally over the past few years. Driving is a structured process requiring the cooperation of several cognitive and psychomotor functions, organized in different levels of complexity. Each of these functions can be affected when Driving Under the Influence (DUI) of SCs. In order to reduce the likelihood of SC-related road accidents, it is essential to understand which areas of psychomotor performance are most affected by these substances, as well as the severity of impairment. For this purpose, a multiple database- literature review of recent experimental studies in humans and animals regarding the psychomotor effects of SCs has been performed. Despite the many limitations connected to experimental studies on humans, results showed a consistency between animal and human data. SCs appear to impair psychomotor performance in humans, affecting different domains related to safe driving even at low doses. Cases of DUI of SC have been repeatedly reported, although the exact prevalence is likely to be underestimated due to current analytical and interpretative issues. For this reason, an accurate physical examination performed by trained and experienced personnel has a primary role in recognizing signs of impairment in case of strong suspicion of SC consumption. The identification of a suspected case should be followed by reliable laboratory examination.

Pharmacokinetic Approach to Combat the Synthetic Cannabinoid PB-22

Synthetic cannabinoids are part of a group of drugs called new psychoactive substances. Most of these cannabinoids are unregulated, and there are no therapeutic treatments for their addictive properties or reversing a potential overdose. Vaccination and catalytic antibodies strategies were investigated to assess their ability to blunt the psychoactive properties of the cannabinoid PB-22. To complement these antibody concentric investigations, we also disclose the discovery of the enzymatic degradation of this cannabinoid. Serum factors including albumin and carboxylesterase were found to catalyze the hydrolysis of PB-22. Affinity, kinetics, animal behavior, and biodistribution studies were utilized to evaluate the efficiency of these pharmacokinetic approaches. Our findings suggest simple antibody binding as the most efficacious means for altering PB-22's effect on the brain. Catalytic approaches only translated to esterases being capable of PB-22's degradation with a catalytic antibody approach providing no proclivity for PB-22's hydrolysis. Pharmacokinetic approaches provide a powerful strategy for treating substance abuse disorders and overdose for drugs where no therapeutic is available.

Sex-dependent pharmacological profiles of the synthetic cannabinoid MMB-Fubinaca

Synthetic cannabinoids have emerged as novel psychoactive substances with damaging consequences for public health. They exhibit high affinity at the cannabinoid type-1 (CB₁ ) receptor and produce similar and often more potent effects as other CB₁ receptor agonists. However, we are still far from a complete pharmacological understanding of these compounds. In this study, by using behavioral, molecular, pharmacological, and electrophysiological approaches, we aimed at characterizing several in vitro and in vivo pharmacological effects of the synthetic cannabinoid MMB-Fubinaca (also known as AMB-Fubinaca or FUB-AMB), a particular synthetic cannabinoid. MMB-Fubinaca stimulates CB₁ receptor-mediated functional coupling to G-proteins in mouse and human brain preparations in a similar manner as the CB₁ receptor agonist WIN55,512-2 but with a much greater potency. Both drugs similarly activate the CB₁ receptor-dependent extracellular signal-regulated kinase (ERK) pathway. Notably, in vivo administration of MMB-Fubinaca in mice induced greater behavioral and electrophysiological effects in male than in female mice in a CB₁ receptor-dependent manner. Overall, these data provide a solid pharmacological profiling of the effects of MMB-Fubinaca and important information about the mechanisms of action underlying its harmful impact in humans. At the same time, they reinforce the significant sexual dimorphism of cannabinoid actions, which will have to be taken into account in future animal and clinical studies.

Social isolation in mice: behavior, immunity, and tumor growth

The aim of this study was to investigate the behavioral, immunological, and neurological effects of long-term isolation in an animal model. Male C3H/eB mice wereraised in either social isolation or standard conditions for 6 weeks. At 10 weeks, each group was further divided into 3 sets. (A) Physical strength and behavior were evaluated with the grip strength, hot plate, staircase, and elevated plus-maze tests. Natural-killer cell activity and lymphocyte proliferation were measured. (B) Half the animals were subjected to electric shock with 3 reminders, and freezing time was evaluated at each reminder. Cortisone levels were evaluated after 16 weeks. (C)Mice were injected with 38 C-13 B lymphoma cells and followed for tumor size and survival. Strength evaluation yielded asignificantly lower body weight and grip strength in the socially isolated mice. Behavioral test results were similar in the two groups. The pattern of reactions to stress conditioning differed significantly, with the socially isolated mice showing an incline in freezing with each successive reminder, and the control mice showing a decline. The socially isolated mice had significantly attenuated tumor growth, with no significant difference in survival from control mice. There were no significant between-group differences in immunological parameters. In conclusion, social isolation serves as a model for chronic stress. It was associated with significant changes in stress conditioning reaction, resembling symptoms of post-traumatic stress disorder, and attenuated tumor development. No differences from controls were found in behavior tests, immune parameters, or survival after tumor cell inoculation.Lay summaryThis article explores biological and behavioral consequences of social isolation in a mice model. Our results show that social isolation leads to changes in the Hypothalamic-hypophyseal-adrenal axis, which in turn alter the response to stress. Additionally, social isolation was shown to impact tumor progression.

Time-restricted feeding alters isoflurane-induced memory deficits

Food consumption during the rest phase promotes circadian desynchrony, which is corrected with harmful physiological and mental disorders. Previously, we found that circadian desynchrony was involved in isoflurane-induced cognitive impairment. Here, we scheduled food access to modulate daily rhythm to examine its impact on isoflurane-induced cognitive impairments. Mice were randomly transferred to restricted feeding (RF) time groups: Control group (Zeitgeber time (ZT) 0–ZT24, ad libitum feeding), Day-Feeding group (ZT0–ZT12, misaligned feeding), and Night-Feeding group (ZT12–ZT24, aligned feeding). Then, some of them were subjected to 5 h of 1.3% isoflurane anaesthesia from ZT14 to ZT19 and were divided into the Control + Anes group, the Day-Feeding + Anes group, and the Night-Feeding + Anes group. Mini-Mitter was used to monitor the daily rhythm. Fear conditioning system was conducted to assess cognition of mice. We observed that the Night-Feeding group adapted to RF gradually, whereas the Day-Feeding group exhibited a disturbed daily rhythm. The Night-Feeding + Anes group exhibited a partially enhanced daily rhythm, whereas the Day-Feeding + Anes group exhibited sustained phase advances and diurnality score increase 7 days after isoflurane anaesthesia. Notably, in tests of hippocampus-dependent contextual memory, the Night-Feeding + Anes group demonstrated decreased deficits; the Day-Feeding + Anes group showed prolonged post-anaesthetic deficits 14 days after isoflurane anaesthesia. However, amygdala-dependent cued-fear conditioning post-anaesthesia was not altered by the RF schedule. In conclusion, we demonstrated that misaligned feeding disturbed the daily rhythm and led to persistent post-anaesthetic cognitive dysfunction. Aligned feeding enhanced the daily rhythm partially and improved post-anaesthetic cognitive dysfunction.

The short-acting synthetic cannabinoid AB-FUBINACA induces physical dependence in mice

BACKGROUND

Recent years have seen a rise in the diversity and use of synthetic cannabinoids. The present study evaluated the behavioral effects of the third-generation indazole-3-carboxamide-type synthetic cannabinoid, AB-FUBINACA.

METHODS

Adult male and female C57BL/6J mice were treated with AB-FUBINACA (0-3 mg/kg, i.p.) and tested repeatedly in the tetrad battery measuring catalepsy, antinociception, hypothermia, and locomotor activity. Mice treated with AB-FUBINACA (≥2 mg/kg, i.p.) displayed classic cannabinoid effects in the tetrad that were blocked by the CB₁ receptor selective antagonist rimonabant. To address tolerance and withdrawal effects, a second group of mice was injected with AB-FUBINACA (3 mg/kg, s.c.) or vehicle consisting of 5% ethanol, 5% Kolliphor EL, and 90 % saline every 12 h and tested daily in modified tetrad over the course of 5 days. On the 6th day, withdrawal was precipitated using rimonabant (3 mg/kg, s.c.), and somatic signs of withdrawal (i.e., head twitches and paw tremors) were quantified.

RESULTS

Although mice did not develop tolerance to AB-FUBINACA or cross-tolerance to Δ⁹-tetrahydrocannabinol (THC; 50 mg/kg, i.p.), somatic precipitated withdrawal signs were observed. Repeated tetrad testing up to 48 h post injection indicated that AB-FUBINACA effects are relatively short-lived, as compared with THC. Brain levels of AB-FUBINACA, as quantified by UHPLC-MS/MS, were undetectable 4 h post injection.

CONCLUSIONS

These data indicate that the cannabinoid effects of AB-FUBINACA are relatively short-lived, yet sufficient to induce dependence in mice.

The role of cannabis in treating anxiety: an update

PURPOSE OF REVIEW

Cannabis use for medical purposes has become increasingly common, including as treatment for mental health disorders such as anxiety. Unfortunately, the evidence examining its use in mental health has been slow to evolve, but is emerging. Given the widespread use of cannabis, it is important for both clinicians and those who suffer with anxiety to understand the effects of cannabis on symptoms of anxiety. In this review, we present recent, available evidence from animal models, clinical trials, and survey studies and evaluate the contribution of these studies to the current understanding of the role of cannabis in treating anxiety.

RECENT FINDINGS

In reviewing recent evidence, we observed significant inconsistencies across findings from preclinical studies. Large-scale surveys suggest that cannabis may be effective in reducing anxiety, however, these results stand in contrast to equivocal findings from clinical trials.

SUMMARY

The literature evaluating the efficacy of cannabis in anxiety disorders is in its infancy. The survey data is generally positive. Although, while some animal studies posit cannabis constituents to have anxiolytic effects, others suggest the opposite or null results. Few new clinical trials have been conducted recently, and the extant trials have significant flaws in methodology. Although anecdotal evidence from survey studies, and a small signal found in animal studies and single-dose clinical trials provide early support that cannabis may be effective for alleviating anxiety, ultimately, the current evidence is equivocal. More high-quality clinical trials must be published before sound conclusions regarding the efficacy of cannabis for treating anxiety can be drawn.

Trazodone and mirtazapine: A possible opioid involvement in their use (at low dose) for sleep?

The efficacy of each antidepressant available has been found equal to that of amitriptyline in double-blind studies. However, a few of them are being prescribed (at under-therapeutic doses) for sleep, in non-depressed persons, when there are relative contraindications for sedative-hypnotics. Following previous studies regarding the antinociceptive mechanisms of various antidepressants, we suggest that the involvement of the opioid system in some of the antidepressants' mechanism of action may contribute to these medications' use for the induction and maintenance of sleep. The mostly prescribed antidepressants for sleep are trazodone (a weak, but specific inhibitor of the synaptosomal uptake of serotonin, that also binds to alpha-1 and alpha-2 adrenoreceptor sites) and mirtazapine (a postsynaptic drug which enhances noradrenergic and 5-HT1A-mediated serotonergic neurotransmission via antagonism of central alpha-2-auto- and hetero-adrenoreceptors). In our previous studies when ICR mice were tested with a hotplate analgesia meter, both trazodone and mirtazapine induced, a naloxone-reversible antinociceptive effect following i.p administration. Summing up the various interactions of trazodone and mirtazapine with opioid, noradrenergic and serotonergic agonists and antagonists, we found that the antinociceptive effect of trazodone is influenced by the opioid receptor subtypes mu and delta (and a clear 5-HT mechanism of antinociception), while the antinociceptive effect of mirtazapine is mainly influenced by kappa and mu opioid receptor subtype (combined with both serotonergic and noradrenergic receptors). This opioid profile of the two drugs may be one of the explanations to their efficacy in the treatment of insomnia, when sedatives (either benzodiazepines or the non-benzodiazepine "Z-compounds") cannot be prescribed.

Effects of the synthetic cannabinoid 5F-AMB on anxiety and recognition memory in mice

RATIONALE

N-[[1-(5-fluoropentyl)-1H-indazol-3-yl]carbonyl]-L-valine methyl ester (5F-AMB) is a synthetic cannabinoid that has been distributed recently. Although inhalation of 5F-AMB produces adverse effects, such as impaired memory and disturbed consciousness, in humans, the psychopharmacological effects of 5F-AMB in rodents have not been investigated.

OBJECTIVES

We first examined the effects of intraperitoneal and intracerebroventricular injections of 5F-AMB on anxiety-like behavior and locomotor activity in the open field (OF) test and recognition memory in the novel object recognition test (NOR) in C57BL/6J mice. We also examined whether a cannabinoid 1 (CB1) receptor antagonist AM251 blocks the effects of 5F-AMB. We next examined the effects of 5F-AMB infusion into the medial prefrontal cortex (mPFC), a brain region associated with anxiety and memory, on these tests.

RESULTS

Intraperitoneal injection of 5F-AMB (0.3 mg/kg) dramatically decreased locomotor activity in the OF, and this effect was partially reversed by AM251 (3 mg/kg). Intracerebroventricular infusion of 5F-AMB (10 nmol) produced an anxiolytic effect in the OF and impaired acquisition, but not retrieval, of recognition memory in the NOR, and these effects were blocked by co-infusion of AM251 (1.8 nmol). Bilateral intra-mPFC infusion of 5F-AMB (10 pmol/side) similarly produced impaired recognition memory acquisition, but no anxiolytic effect.

CONCLUSIONS

The results demonstrate that centrally administered 5F-AMB produces anxiolytic effect and impaired recognition memory acquisition via activation of CB1 receptors, while systemic 5F-AMB severely impaired locomotor activity. The mPFC is involved in 5F-AMB-induced impairment of recognition memory acquisition. However, other brain region(s) may contribute to the 5F-AMB-induced anxiolytic effect.

Potential Mechanisms Underlying the Deleterious Effects of Synthetic Cannabinoids Found in Spice/K2 Products

The chief psychoactive constituent of many bioactive phytocannabinoids (Δ⁹-tetrahydrocannabinol, Δ⁹-THC) found in hemp, cannabis or marijuana plants are scientifically denoted by the Latin term, Cannabis sativa, acts on cell surface receptors. These receptors are ubiquitously expressed. To date, two cannabinoid receptors have been cloned and characterized. Cannabinoid receptor type 1 (CB1R) is found to serve as the archetype for cannabinoid action in the brain. They have attracted wide interest as the mediator of all psychoactive properties of exogenous and endogenous cannabinoids and they are abundantly expressed on most inhibitory and excitatory neurons. Recent evidence established that cannabinoid receptor type 2 (CB2R) is also expressed in the neurons at both presynaptic and postsynaptic terminals and are involved in neuropsychiatric effects. Distinct types of cells in many regions in the brain express CB2Rs and the cellular origin of CB2Rs that induce specific behavioral effects are emerging. To mimic the bliss effects of marijuana, synthetic cannabinoids (SCBs) have been sprayed onto plant material, and this plant material has been consequently packaged and sold under brand name “Spice” or “K2”. These SCBs have been shown to maintain their affinity and functional activity for CB1R and CB2R and have been shown to cause severe harmful effects when compared to the effects of Δ⁹-THC. The present review discusses the potential brain mechanisms that are involved in the deleterious effects of SCBs.

The Chemistry and Pharmacology of Synthetic Cannabinoid Receptor Agonist New Psychoactive Substances: Evolution

Synthetic cannabinoid receptor agonists (SCRAs) are the largest and most structurally diverse class of new psychoactive substances (NPS). Although the earliest SCRA NPS were simply repurposed from historical academic manuscripts or pharmaceutical patents describing cannabinoid ligands, recent examples bear hallmarks of rational design. SCRA NPS manufacturers have applied traditional medicinal chemistry strategies (such as molecular hybridization, bioisosteric replacement, and scaffold hopping) to existing cannabinoid templates in order to generate new molecules that circumvent structure-based legislation. Most SCRAs potently activate cannabinoid type 1 and type 2 receptors (CB₁ and CB₂, respectively), with the former contributing to the psychoactivity of these substances. SCRAs are generally more toxic than the Δ⁹-tetrahydrocannabinol (Δ⁹-THC) found in cannabis, and this may be due to ligand bias, metabolism, or off-target activity. This chapter will chart the evolution of recently identified SCRA NPS chemotypes, as well as their putative manufacturing by-products and thermolytic degradants, and describe structure-activity relationships within each class.