Apparent CB₁ Receptor Rimonabant Affinity Estimates: Combination with THC and Synthetic Cannabinoids in the Mouse In...

Synthetic cannabinoids (SCs) represent an emerging class of abused drugs associated with psychiatric complications and other substantial health risks. These ligands are largely sold over the internet for human consumption, presumably because of their high cannabinoid 1 receptor (CB₁R) affinity and their potency in eliciting pharmacological effects similar to Δ⁹-tetrahydrocannabinol (THC), as well as circumventing laws illegalizing this plant. Factors potentially contributing to the increased prevalence of SC abuse and related hospitalizations, such as increased CB₁R efficacy and non-CB₁R targets, highlight the need for quantitative pharmacological analyses to determine receptor mediation of the pharmacological effects of cannabinoids. Accordingly, the present study used pA₂ and pK_B analyses for quantitative determination of CB₁R mediation in which we utilized the CB₁R-selective inverse agonist/antagonist rimonabant to elicit rightward shifts in the dose-response curves of five SCs (i.e., A-834,735D; WIN55,212-2; CP55,950; JWH-073; and CP47,497) and THC in producing common cannabimimetic effects (i.e., catalepsy, antinociception, and hypothermia). The results revealed overall similarity of pA₂ and pK_B values for these compounds and suggest that CB₁Rs, and not other pharmacological targets, largely mediated the central pharmacological effects of SCs. More generally, affinity estimation offers a powerful pharmacological approach to assess potential receptor heterogeneity subserving in vivo pharmacological effects of SCs.