The psychostimulant (±)-cis-4,4′-dimethylaminorex (4,4′-DMAR) interacts with human plasmalemmal and vesicular monoamine transporters

Abstract

(±)-cis-4,4'-Dimethylaminorex (4,4'-DMAR) is a new psychoactive substance (NPS) that has been associated with 31 fatalities and other adverse events in Europe between June 2013 and February 2014. We used in vitro uptake inhibition and transporter release assays to determine the effects of 4,4'-DMAR on human high-affinity transporters for dopamine (DAT), norepinephrine (NET) and serotonin (SERT). In addition, we assessed its binding affinities to monoamine receptors and transporters. Furthermore, we investigated the interaction of 4,4'-DMAR with the vesicular monoamine transporter 2 (VMAT2) in rat phaeochromocytoma (PC12) cells and synaptic vesicles prepared from human striatum. 4,4'-DMAR inhibited uptake mediated by human DAT, NET or SERT, respectively in the low micromolar range (IC values < 2 μM). Release assays identified 4,4'-DMAR as a substrate type releaser, capable of inducing transporter-mediated reverse transport via DAT, NET and SERT. Furthermore, 4,4'-DMAR inhibited both the rat and human isoforms of VMAT2 at a potency similar to 3,4-methylenedioxymethylamphetamine (MDMA). This study identified 4,4'-DMAR as a potent non-selective monoamine releasing agent. In contrast to the known effects of aminorex and 4-methylaminorex, 4,4'-DMAR exerts profound effects on human SERT. The latter finding is consistent with the idea that fatalities associated with its abuse may be linked to monoaminergic toxicity including serotonin syndrome. The activity at VMAT2 suggests that chronic abuse of 4,4'-DMAR may result in long-term neurotoxicity.

Designer drugs: mechanism of action and adverse effects

“…In human transporter-transfected cells that were preloaded with monoamines and exposed to drugs at a single high concentration (100 lM), only dopamine efflux was observed for 4,4 0 -DMAR, and dopamine and 5-HT efflux was observed for 4-MAR (Rickli et al 2019). In addition to interactions with plasmalemmal transporters, 4,4 0 -DMAR has been shown to inhibit human VMAT2-mediated dopamine uptake (Maier et al 2018b). In addition to their primary effects on transporters, minor interactions with serotonergic 5-HT 2C and adrenergic a 2A receptors have been described for 4-MAR, and low affinity at 5-HT 2A and 5-HT 2C receptors has been described for 4,4 0 -DMAR (Maier et al 2018b;Rickli et al 2019).…”

“…In human transporter-transfected cells, 4,4 0 -DMAR is a potent inhibitor of norepinephrine, dopamine, and 5-HT reuptake. 4-MAR has similarly potent dopamine and norepinephrine reuptake properties as 4,4 0 -DMAR, but 5-HT uptake inhibition is less pronounced compared with its para-methylated counterpart (Maier et al 2018b;Rickli et al 2019). Aminorex and its derivative 4-MAR mediate norepinephrine and dopamine efflux in rat synaptosomes, with weak substrate activity at the SERT (Brandt et al 2014;Rothman et al 2001).…”

“…4,4 0 -DMAR and 3 0 ,4 0methylenedioxy-4-methylaminorex (MDMAR) induce norepinephrine, dopamine, and 5-HT efflux in rat synaptosomes (Brandt et al 2014;McLaughlin et al 2015). Dynamic superfusion experiments revealed the substrate activity of 4,4 0 -DMAR at human monoamine transporters (Maier et al 2018b). In human transporter-transfected cells that were preloaded with monoamines and exposed to drugs at a single high concentration (100 lM), only dopamine efflux was observed for 4,4 0 -DMAR, and dopamine and 5-HT efflux was observed for 4-MAR (Rickli et al 2019).…”

“…In addition to interactions with plasmalemmal transporters, 4,4 0 -DMAR has been shown to inhibit human VMAT2-mediated dopamine uptake (Maier et al 2018b). In addition to their primary effects on transporters, minor interactions with serotonergic 5-HT 2C and adrenergic a 2A receptors have been described for 4-MAR, and low affinity at 5-HT 2A and 5-HT 2C receptors has been described for 4,4 0 -DMAR (Maier et al 2018b;Rickli et al 2019).…”

Characterization of a recently detected halogenated aminorex derivative: para-fluoro-4-methylaminorex (4′F-4-MAR)

“…In 2014, para-methyl-4-methylaminorex (4,4′-DMAR) (Fig. 1), a novel 4-MAR derivative, was reported and characterized 15,27 . Together with Europol, EMCDDA published an early warning notification in 2014, notifying of the involvement of 4,4′-DMAR in several deaths in Europe, 8 of them in Hungary (June 2013) and 18 in the United Kingdom (between June and December 2013) 28 .…”