Sixty new psychoactive substances (NPS) and their metabolites, including opioids, cannabinoids, and serotonergic hallucinogens, were screened for their ability to activate μ-opioid, CB1, 5-HT1A, and 5-HT2A receptors. Most substances activated their intended target receptor. Among μ-opioid agonists, 2-fluorofentanyl (EC50 = 1.0 nM), carfentanil (EC50 = 2.7 nM), and acrylfentanyl (EC50 = 2.8 nM) were the most potent, with a >1500-fold potency range across compounds. Furanylfentanyl, 4-methoxybutyrylfentanyl, and valerylfentanyl acted as partial agonists. On the 5-HT2A receptor, bromo-dragonfly was the most potent (EC50 = 0.05 nM, 400 times more potent than LSD), followed by NBOMe compounds (EC50 0.11–1.3 nM). Off-target μ-opioid activation occurred for piperazines, phenethylamines, and tryptamines. The synthetic cannabinoid metabolite 3-carboxy indole PB-22 activated 5-HT2A. Bromo-dragonfly activated all four receptors. These findings highlight complex, often overlapping targets among NPS.
Synthetic cathinones, a large class of new psychoactive substances, primarily inhibit dopamine, norepinephrine, and serotonin transporters, with high dopamine transporter selectivity linked to abuse potential. In vitro testing of 58 substances showed that N-pyrrolidine cathinones combined with methylenedioxy groups—MDPiHP, MDPEP, and MDPV—had the highest potency at the dopamine transporter. Other N-pyrrolidine cathinones, such as 3F-α-PHP, 3F-α-PiHP, and 4F-α-PiHP, showed the greatest dopamine transporter selectivity relative to the serotonin transporter. Chloromethcathinone and methylmethcathinone compounds, like 3-CMC, displayed an amphetamine-like profile with comparable potency at dopamine and norepinephrine transporters. Some cathinones at high concentrations and phenethylamines at micromolar concentrations also activated the 5-HT2A receptor, while 2C-like arylcyclohexylamines targeted the receptor without transporter inhibition. The majority of compounds, especially N-pyrrolidine cathinones, suggest high abuse potential based on their dopamine transporter selectivity.