Background and Purpose: We sought to understand why (−)‐cannabidiol (CBD) and (−)‐cannabidiol‐dimethylheptyl (CBD‐DMH) exhibit distinct pharmacology, despite near identical structures.Experimental Approach: HEK293A cells expressing either human type 1 cannabinoid (CB₁) receptors or CB₂ receptors were treated with CBD or CBD‐DMH with or without the CB₁ and CB₂ receptor agonist CP55,940, CB₁ receptor allosteric modulator Org27569 or CB₂ receptor inverse agonist SR144528. Ligand binding, cAMP levels and βarrestin1 recruitment were measured. CBD and CBD‐DMH binding was simulated with models of human CB₁ or CB₂ receptors, based on the recently published crystal structures of agonist‐bound (5XRA) or antagonist‐bound (5TGZ) human CB₁ receptors.Key Results: At CB₁ receptors, CBD was a negative allosteric modulator (NAM), and CBD‐DMH was a mixed agonist/positive allosteric modulator. CBD and Org27569 shared multiple interacting residues in the antagonist‐bound model of CB₁ receptors (5TGZ) but shared a binding site with CP55,940 in the agonist‐bound model of CB₁ receptors (5XRA). The binding site for CBD‐DMH in the CB₁ receptor models overlapped with CP55,940 and Org27569. At CB₂ receptors, CBD was a partial agonist, and CBD‐DMH was a positive allosteric modulator of cAMP modulation but a NAM of βarrestin1 recruitment. CBD, CP55,940 and SR144528 shared a binding site in the CB₂ receptor models that was separate from CBD‐DMH.Conclusion and Implications: The pharmacological activity of CBD and CBD‐DMH in HEK293A cells and their modelled binding sites at CB₁ and CB₂ receptors may explain their in vivo effects and illuminates the difficulties associated with the development of allosteric modulators for CB₁ and CB₂ receptors.Linked Articles: This article is part of a themed section on 8^th European Workshop on Cannabinoid Research. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.10/issuetoc

The Cannabis sativa plant contains more than 120 cannabinoids. With the exceptions of ∆⁹-tetrahydrocannabinol (∆⁹-THC) and cannabidiol (CBD), comparatively little is known about the pharmacology of the less-abundant plant-derived (phyto) cannabinoids. The best-studied transducers of cannabinoid-dependent effects are type 1 and type 2 cannabinoid receptors (CB1R, CB2R). Partial agonism of CB1R by ∆⁹-THC is known to bring about the ‘high’ associated with Cannabis use, as well as the pain-, appetite-, and anxiety-modulating effects that are potentially therapeutic. CB2R activation by certain cannabinoids has been associated with anti-inflammatory activities. We assessed the activity of 8 phytocannabinoids at human CB1R, and CB2R in Chinese hamster ovary (CHO) cells stably expressing these receptors and in C57BL/6 mice in an attempt to better understand their pharmacodynamics. Specifically, ∆⁹-THC, ∆⁹-tetrahydrocannabinolic acid (∆⁹-THCa), ∆⁹-tetrahydrocannabivarin (THCV), CBD, cannabidiolic acid (CBDa), cannabidivarin (CBDV), cannabigerol (CBG), and cannabichromene (CBC) were evaluated. Compounds were assessed for their affinity to receptors, ability to inhibit cAMP accumulation, βarrestin2 recruitment, receptor selectivity, and ligand bias in cell culture; and cataleptic, hypothermic, anti-nociceptive, hypolocomotive, and anxiolytic effects in mice. Our data reveal partial agonist activity for many phytocannabinoids tested at CB1R and/or CB2R, as well as in vivo responses often associated with activation of CB1R. These data build on the growing body of literature showing cannabinoid receptor-dependent pharmacology for these less-abundant phytocannabinoids and are critical in understanding the complex and interactive pharmacology of Cannabis-derived molecules.

The first synthetic cannabinoid receptor agonists (SCRAs) were designed as tool compounds to study the endocannabinoid system’s two predominant cannabinoid receptors, CB1R and CB2R. Unfortunately, novel SCRAs now represent the most rapidly proliferating novel psychoactive substances (NPS) of abuse globally. Unlike ∆⁹-tetrahydrocannabinol, the CB1R and CB2R partial agonist and the intoxicating constituent of Cannabis, many SCRAs characterized to date are full agonists of CB1R. Gaining additional insight into the pharmacological activity of these SCRAs is critical to assess and regulate NPSs as they enter the marketplace. The purpose of this study was to assess select SCRAs recently identified by Canadian police, border service agency, private companies and the illicit market as potential CB1R and CB2R agonists. To this end, fifteen SCRAs were screened for in vitro activity and in silico interactions at CB1R and CB2R. Several SCRAs were identified as being highly biased for cAMP inhibition or βarrestin2 recruitment and receptor subtype selectivity between CB1R and CB2R. The indazole ring and halogen-substituted butyl or pentyl moieties were identified as two structural features that may direct βarrestin2 bias. Two highly-biased SCRAs—JWH-018 2′-napthyl-N-(3-methylbutyl) isomer (biased toward cAMP inhibition) and 4-fluoro MDMB-BINACA (biased toward βarrestin2 recruitment) displayed unique and differential in vivo activity in mice. These data provide initial insight into the correlations between structure, signalling bias, and in vivo activity of the SCRAs.

Cannabis sativa has gained popularity as a “natural substance”, leading many to falsely assume that it is not harmful. This assumption has been documented amongst pregnant mothers, many of whom consider Cannabis use during pregnancy as benign. The purpose of this study was to validate a Cannabis smoke exposure model in pregnant rats by determining the plasma levels of cannabinoids and associated metabolites in the dams after exposure to either Cannabis smoke or injected cannabinoids. Maternal and fetal cytokine and chemokine profiles were also assessed after exposure. Pregnant Sprague–Dawley rats were treated daily from gestational day 6–20 with either room air, i.p. vehicle, inhaled high-Δ⁹-tetrahydrocannabinol (THC) (18% THC, 0.1% cannabidiol [CBD]) smoke, inhaled high-CBD (0.7% THC, 13% CBD) smoke, 3 mg/kg i.p. THC, or 10 mg/kg i.p. CBD. Our data reveal that THC and CBD, but not their metabolites, accumulate in maternal plasma after repeated exposures. Injection of THC or CBD was associated with fewer offspring and increased uterine reabsorption events. For cytokines and chemokines, injection of THC or CBD up-regulated several pro-inflammatory cytokines compared to control or high-THC smoke or high-CBD smoke in placental and fetal brain tissue, whereas smoke exposure was generally associated with reduced cytokine and chemokine concentrations in placental and fetal brain tissue compared to controls. These results support existing, but limited, knowledge on how different routes of administration contribute to inconsistent manifestations of cannabinoid-mediated effects on pregnancy. Smoked Cannabis is still the most common means of human consumption, and more preclinical investigation is needed to determine the effects of smoke inhalation on developmental and behavioural trajectories.