AMB‐FUBINACA (FUB‐AMB) and related "spice" compounds induce gene‐dose effects in mice lacking cannabinoid‐1 receptor (CB1R) alleles

Abstract

Synthetic cannabinoids (SCs), commonly known as ‘K2' or 'spice’, are a constantly evolving class of new psychoactive substances that pose public health risks. Little information is available about novel SCs when they first emerge into the recreational drug marketplace. In this study, we investigated the pharmacology of AMB‐FUBINACA (FUB‐AMB) and 5F‐AMB, two recently encountered indazole‐based SCs responsible for mass intoxications and fatalities. The effects of known cannabinoid‐1 receptor (CB1R) agonists AM‐2201 and Δ9‐THC were examined for comparison. Groups of genetically‐engineered mice lacking CB1R alleles (CB1R −/− and CB1R +/−), and their C57Bl/6J wild‐type (WT) counterparts, received surgically‐implanted subcutaneous (s.c.) temperature transponders under isoflurane anesthesia. Beginning one week after surgery, mice received s.c. injection of either SCs or vehicle and were subjected to a “triad” test battery consisting of sequential assessment of: 1] body temperature, 2] catalepsy bar latency and 3] hot‐plate analgesia latency. All SCs induced significant dose‐ and time‐dependent hypothermia, catalepsy and analgesia in WT mice, which lasted up to 120 min. The rank order of potency was FUB‐AMB>5F‐AMB=AM‐2201>Δ9‐THC. Importantly, ED50 values in the triad test battery for FUB‐AMB (0.09–0.22 mg/kg, s.c.) were at least 50‐fold more potent than those associated with Δ9‐THC (12.72–30.37 mg/kg, s.c.), and SCs were more efficacious in their ability to produce hypothermia. Homozygous CB1R −/− mice were not affected by any dose of the compounds tested, whereas heterozygous CB1R +/− mice displayed responses intermediate between homozygous and WT. CB1R binding assays in WT mouse brain revealed that IC50 values for inhibition of [3H]SR141716 binding were 1.2, 2.2, 12.6 and 50.6 nM for FUB‐AMB, AM‐2201, 5F‐AMB and Δ9‐THC, respectively. Our findings demonstrate that newer indazole‐based SCs exert their effects via potent agonist actions at CB1R, and do not support the notion that SCs induce in vivo effects by non‐CB receptor mechanisms. Given the widespread abuse of synthetic cannabinoids, CB1R antagonists should be made available for overdose rescue, and medical marijuana could be deployed as an agonist treatment for dependence on these substances.Support or Funding InformationThis research was generously supported by IRP, NIDA, NIH (DA00523)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.