Comprehensive in vitro profiling of traditional and emerging stimulants at monoamine transporters and the 5-HT2A receptor.

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.

Study at a glance

Abstract

New psychoactive substances (NPSs) often emerge on the illicit drug market with limited pharmacological or toxicological data. Synthetic cathinones are the second largest NPS group, often mimicking the effects of classical stimulants such as cocaine and methylenedioxymethamphetamine (MDMA). Such stimulants primarily target dopamine (DAT), norepinephrine (NET) and serotonin (SERT) transporters, with DAT selectivity being linked to abuse potential. Owing to the lack of pharmacological profiling, this study aimed to determine the potencies and structure-activity relationships (SARs) of recently emerged stimulants. Employing in vitro human transporter inhibition assay and AequoScreen® 5-HT2A receptor activity assay, the potency, transporter selectivity, DAT/SERT, DAT/NET, and NET/SERT ratios, and group-wide SARs of 58 substances were investigated. Most synthetic cathinones inhibited DAT at nanomolar concentrations, with N-pyrrolidine cathinones in combination with methylenedioxy groups-4-methylenedioxy-α-pyrrolidino-isohexanophenone (MDPiHP), 3,4-methylenedioxy PV8 (MDPEP), and 3,4-methylenedioxy pyrovalerone (MDPV)-demonstrating the highest DAT potency among all the tested stimulants. In contrast, other N-pyrrolidine cathinones, 3F-α-PHP, 3F-α-PiHP and 4F-α-PiHP, exhibited the highest DAT selectivity (DAT/SERT ratio). Chloromethcathinone (CMC) and methylmethcathinone (MMC) compounds, such as 3-CMC, exhibited a distinct amphetamine-like pharmacological uptake inhibition profile showing a comparable potency between DAT and NET. Some cathinones at high concentrations and phenethylamines in micromolar concentrations additionally activated the 5-HT2A receptor, whereas 2C-like arylcyclohexylamines primarily targeted the receptor without transporter inhibition. These results show that cathinones displayed distinct group SARs. Based on the DAT/SERT selectivity, the majority of the investigated compounds, especially N-pyrrolidine cathinones, suggest a high abuse potential.