Structure-Activity relationship of novel second-generation synthetic cathinones: Mechanism of action, locomotion, reward, and immediate-early genes

Several new synthetic cathinones, which mimic the effect of classical psychostimulants such as cocaine or MDMA, have appeared in the global illicit drug market in the last decades. In fact, the illicit drug market is continually evolving by constantly adding small modifications to the common chemical structure of synthetic cathinones. Thus, the aim of this study was to investigate the in vitro and in vivo structure-activity relationship of six novel synthetic cathinones currently popular as recreational drugs, Pentedrone, Pentylone, N-ethyl-pentedrone (NEPD), N-ethyl-pentylone (NEP), 4-methyl-pentedrone (4-MPD) and 4-methyl-ethylaminopentedrone (4-MeAP), which structurally differ in the absence or presence of different aromatic substituents and in their amino terminal group. Human embryonic kidney cells (HEK293) expressing the human isoforms of SERT and DAT were used for the uptake inhibition and release assays. Moreover, Swiss-CD-1 mice were used to investigate their psychostimulant effect, rewarding properties (3, 10 and 30 mg/kg, i.p.) and the induction of immediate-early genes (IEGs) such as arc and c-fos in dorsal (DS) and ventral striatum (VS) as well as bdnf in medial prefrontal cortex (mPFC). Our results demonstrated that all tested synthetic cathinones are potent dopamine (DA) uptake inhibitors, especially the N-ethyl analogues, while the ring-substituted cathinones tested showed higher potency as SERT inhibitors than their no ring-substituted analogues. Moreover, unlike NEP, all tested compounds showed 'hybrid' properties, acting as DAT blockers but SERT substrates. Regarding the locomotion, NEP and NEPD were more efficacious (10 mg/kg) than their N-methyl analogues, which correlates with their higher potency inhibiting DAT and an overexpression of arc levels in DS and VS. Furthermore, all compounds tested induced an increase in c-fos expression in DS, except for 4-MPD, the least effective compound at inducing hyperlocomotion. Moreover, NEP induced an up-regulation of bdnf in mPFC that correlates whit its 5-HTergic properties. Finally, the present study demonstrated for the first time that pentylone, NEP, 4-MPD and 4-MeAP induce reward in mice. Altogether, this study provides valuable information about the mechanism of action, psychostimulant and rewarding properties as well as changes in the expression of IEGs related to addiction induced by novel second-generation synthetic cathinones

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

(±)-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; 50; 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

Structural basis of organic cation transporter-3 inhibition

Organic cation transporters (OCTs) facilitate the translocation of catecholamines, drugs and xenobiotics across the plasma membrane in various tissues throughout the human body. OCT3 plays a key role in low-affinity, high-capacity uptake of monoamines in most tissues including heart, brain and liver. Its deregulation plays a role in diseases. Despite its importance, the structural basis of OCT3 function and its inhibition has remained enigmatic. Here we describe the cryo-EM structure of human OCT3 at 3.2 Å resolution. Structures of OCT3 bound to two inhibitors, corticosterone and decynium-22, define the ligand binding pocket and reveal common features of major facilitator transporter inhibitors. In addition, we relate the functional characteristics of an extensive collection of previously uncharacterized human genetic variants to structural features, thereby providing a basis for understanding the impact of OCT3 polymorphisms.ISSN:2041-172