Neurochemical pharmacology of psychoactive substituted N-benzylphenethylamines: High potency agonists at 5-HT_2A receptors

The use of new psychoactive substituted 2,5-dimethoxy-N-benzylphenethylamines is associated with abuse and toxicity in the United States and elsewhere and their pharmacology is not well known. This study compares the mechanisms of action of 2-(2,5-dimethoxy-4-methylphenyl)-N-(2-methoxybenzyl)ethanamine (25D-NBOMe), 2-(4-ethyl-2,5-dimethoxyphenyl)-N-(2-methoxybenzyl)ethanamine (25E-NBOMe), 2-(2,5-dimethoxyphenyl)-N-(2-methoxybenzyl)ethanamine (25H-NBOMe), 2-(((4-iodo-2,5-dimethoxyphenethyl)amino)methyl)phenol (25I-NBOH); and 2-(2,5-dimethoxy-4-nitrophenyl)-N-(2-methoxybenzyl)ethanamine) (25N-NBOMe) with hallucinogens and stimulants. Mammalian cells heterologously expressing 5-HT_1A, 5-HT_2A, 5-HT_2B or 5-HT_2C receptors, or dopamine, serotonin or norepinephrine transporters (DAT, SERT and NET, respectively) were used to assess drug affinities at radioligand binding sites. Potencies and efficacies were determined using [³⁵S]GTPγS binding assays (5-HT_1A), inositol-phosphate accumulation assays (5-HT_2A 5-HT_2B and 5-HT_2C), and uptake and release assays (transporters). The substituted phenethylamines were very low potency and low efficacy agonists at the 5-HT_1A receptor. 25D-NBOMe, 25E-NBOMe, 25H-NBOMe, 25I-NBOH and 25N-NBOMe had very high affinity for, and full efficacy at, 5-HT_2A and 5-HT_2C receptors. In the 5-HT_2A receptor functional assay, 25D-NBOMe, 25E-NBOMe, 25I-NBOH and 25N-NBOMe had subnanomolar to low nanomolar potencies similar to (+)lysergic acid diethylamide (LSD) while 25H-NBOMe had lower potency, similar to serotonin. At the 5-HT_2C receptor, four had very high potencies, similar to LSD and serotonin, while 25H-NBOMe had lower potency. At the 5-HT_2B receptor, the compounds had lower affinity, potency and efficacy compared to 5-HT_2A or 5-HT_2C. The phenethylamines had low to mid micromolar affinities and potencies at the transporters. These results demonstrate that these –NBOMe and –NBOH substituted phenethylamines have a biochemical pharmacology consistent with hallucinogenic activity, with little psychostimulant activity.