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

Abstract

BACKGROUND AND PURPOSE: 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.

EXPERIMENTAL APPROACH: 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.

KEY RESULTS: 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.

CONCLUSIONS AND IMPLICATIONS: 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.