Using in vitro norepinephrine transporter (NET) inhibition and 5‐HT 2 receptor binding data to predict psychoactive doses of novel psychoactive substances in humans

Summary

For amphetamine-type novel psychoactive substances (NPS), the potency of inhibiting the norepinephrine transporter (NET) in cells correlated significantly with the doses people typically use to get psychoactive effects, while inhibition of dopamine or serotonin transporters did not. For hallucinogenic NPS and classic hallucinogens (tryptamines, phenethylamines), binding affinity at the serotonin 5-HT2A receptor strongly predicted human psychoactive dose; binding at 5-HT2C did so less strongly, and 5-HT1A showed no relationship. In vitro pharmacological profiling of NET inhibition and 5-HT2 receptor binding may help estimate psychoactive doses of new substances, though factors like metabolism and brain penetration also matter.

Study at a glance

Abstract

Objective Novel psychoactive substances (NPS) or “bath salts” are increasingly sold over the Internet and used as substitutes for classic recreational substances. Previous studies showed that classic amphetamine‐type stimulants most potently act on the norepinephrine (NE) compared to the dopamine (DA) and serotonin (5‐HT) system and NE activation correlated with the subjective effects across classic amphetamine‐type substances. Additionally, NE has been shown to critically mediate the subjective and cardiostimulant effects of 3,4‐methylenedioxymethamphetamine (MDMA). On the other hand subjective effects of classic serotonergic hallucinogens such as LSD or psilocybin have been shown to depend on serotonin 5‐HT 2A receptor stimulation. The aim of the present study was to characterize the role of the NE, DA, and 5‐HT transporters (NET, DAT, and SERT, respectively) in the acute effects of novel psychoactive substances with amphetamine‐like structures as well as the role of the 5‐HT 2 receptors in the psychoactivity of novel hallucinogens. Methods First, we assessed the 3 H‐monoamine uptake inhibition potency in a series of 33 NPS and classic amphetamine‐like substances in HEK 293 cells expressing the human NET, DAT, and SERT. We also assessed radioligand‐binding at the 5‐HT 1A , 5‐HT 2A , and 5‐HT 2C receptor of 20 classic and novel designer hallucinogens of the ergoline, tryptamine, phenethylamine, or benzodifuran class. Second, we collected information on the typically used oral doses of all these substances as reported in substance user forums or where available from clinical studies in humans. The in vitro monoamine transporter inhibition potency and 5‐HT receptor binding affinity data was then correlated with the doses used in humans to induce subjective psychotropic effects. Results The amphetamine‐type substances showed a wide range of monoamine transporter inhibition potencies indicating large variability in the pharmacology of amphetamine‐type NPS (Table). Typically, inhibition of the DAT and NET was observed in NPS with reportedly stimulant‐type clinical effects. Specifically, we found that the NET inhibition potency in vitro correlated significantly with the doses used by humans (R=0.50, P<0.01, N=33) while DAT or SERT inhibition potency showed no such association with the doses used (R=0.23, NS, N=33 and R=−0.26, NS, N=33). Thus, the pharmacological characteristic of NET inhibition in vitro best predicted the human psychoactive dose of the NPS indicating a role for the NET in the psychoactive effects of novel amphetamine‐type substances. The clinical potency of hallucinogenic NPS and classic hallucinogens (tryptamines, hallucinogenic phenethylamines) was correlated with high significance with the binding affinity at serotonergic 5‐HT 2A (R=0.74, P<0.001, N=20), less strongly also 5‐HT 2C (R=0.66, P<0.01, N=20) but not 5‐HT 1A (R=0.09, NS, N=20) receptors. Conclusion NET inhibition potency in vitro may be a useful characteristic of NPS to predict their psychoactive doses in humans. Similarly, in vitro 5‐HT 2 receptor binding data of receptor agonists can be used to estimate whether novel substances likely exhibit hallucinogen‐like psychoactive effects in humans and to provide dose estimates. In vitro pharmacological profiling is critical for the assessment of novel psychoactive substances but additional aspects such as route of administration, metabolism, and brain penetration also need to be studied. Support or Funding Information This work was supported by the Swiss Federal Office of Public Health. This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .