Stereochemical effects of 11-OH-delta 8-tetrahydrocannabinol-dimethylheptyl to inhibit adenylate cyclase and bind to the cannabinoid receptor.

The recent preparation of the enantiomers of 11-OH-delta 8-tetrahydrocannabinol-dimethylheptyl (THC-DMH), recrystallized to absolute enantiomeric purity, has made it possible to examine the requirement for stereospecificity for the interaction of this component with the cannabinoid receptor, defined by the binding of [3H]CP-55,940 and the adenylate cyclase enzyme. The enantiomer (-)11-OH-delta 8-THC-DMH exhibited a fully efficacious and potent (IC50 = 1.8 nM) inhibition of the accumulation of cAMP in intact N18TG2 cells. The (-)enantiomer was as efficacious and potent (Kinh = 7.2 nM) as desacetyllevonantradol in inhibiting adenylate cyclase activity in membrane preparations. The (-)enantiomer was able to compete fully for the specific binding of [3H]CP-55,940 to membranes from the brain of the rat in homologous displacement studies (Ki = 234 pM). The potency ratios exhibited by the (-) to (+)enantiomers of 11-OH-delta 8-THC-DMH exceeded 1000 for each of these activities.