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Harald H. Sitte

15 papers in the library · 375 citations · publishing 2011-2026

Papers

The mechanistic basis for noncompetitive ibogaine inhibition of serotonin and dopamine transporters.

The Journal of biological chemistry May 25, 2012 Simon Bulling, Klaus Schicker, Yuan-Wei Zhang et al. 124 citations

Ibogaine, a hallucinogenic alkaloid proposed as a treatment for opiate withdrawal, inhibits the serotonin transporter (SERT) through a noncompetitive mechanism, unlike all other known inhibitors which compete with serotonin. It binds to a distinct site accessible from the cell exterior, not the substrate-binding site, and increases accessibility in the cytoplasmic permeation pathway. Ibogaine also noncompetitively inhibits the dopamine transporter (DAT) and blocks substrate-induced currents in both transporters. The inhibition is not reversed by increasing substrate concentration, and ibogaine does not form a long-lived complex with SERT but binds directly to the inward-open conformation. A kinetic model distinguishes ibogaine's noncompetitive action from cocaine's competitive action.

The ugly side of amphetamines: short- and long-term toxicity of 3,4-methylenedioxymethamphetamine (MDMA, ‘Ecstasy’), methamphetamine and d-amphetamine

Biological Chemistry January 2, 2011 Thomas Steinkellner, Michael Freissmuth, Harald H. Sitte et al. 112 citations

Amphetamines like speed, ice, and ecstasy are widely abused for their euphoric and stimulant effects. While animal studies show strong evidence that MDMA causes chronic neurotoxicity, the physiological consequences in humans remain unclear. Differences in metabolism and pharmacokinetics between species and animal strains make it difficult to design realistic human dose paradigms in animal research. This review examines amphetamine toxicity, especially MDMA toxicity, in the context of human disease, setting aside confounding factors such as polydrug use and drug purity.

Fluorinated phenmetrazine “legal highs” act as substrates for high-affinity monoamine transporters of the SLC6 family

Neuropharmacology October 12, 2017 Felix P. Mayer, Nadine V. Burchardt, Ann M Decker et al. 30 citations

Three isomers of the new psychoactive substance 3-fluorophenmetrazine (2-FPM, 3-FPM, and 4-FPM) inhibit dopamine and norepinephrine transporters with potencies comparable to cocaine (IC50 values below 2.5 μM) but show much weaker effects at the serotonin transporter (IC50 values above 80 μM). They also induce efflux of monoamines via all three transporters, an effect enhanced by the ionophore monensin. These compounds act as monoamine releasers with marked potency at catecholamine transporters implicated in abuse and addiction.

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

Neuropharmacology June 23, 2018 Julian Maier, Felix P. Mayer, Dino Luethi et al. 24 citations

4,4′-DMAR, a new psychoactive substance linked to 31 deaths in Europe between June 2013 and February 2014, acts as a potent non-selective monoamine releasing agent. It inhibits dopamine, norepinephrine, and serotonin transporters at low micromolar concentrations (IC50 values below 2 μM) and induces reverse transport via these transporters. It also inhibits the vesicular monoamine transporter 2 in both rat and human cells with potency similar to MDMA. Unlike aminorex and 4-methylaminorex, 4,4′-DMAR strongly affects the serotonin transporter, suggesting fatalities may involve monoaminergic toxicity including serotonin syndrome. Its activity at VMAT2 indicates potential long-term neurotoxicity with chronic abuse.

Structure-activity relationships of serotonergic 5-MeO-DMT derivatives: insights into psychoactive and thermoregulatory properties

Molecular Psychiatry March 14, 2024 Pol Puigseslloses, Gabriel Ketsela, Nicola Weiss et al. 23 citations

All tested 5-MeO-tryptamines selectively bind to 5-HT1A receptors over 5-HT2A receptors, with computational docking predicting better interaction in the 5-HT1A binding pocket. These compounds also interact with the serotonin transporter (SERT), where molecular size of the amino group influences affinity. 5-MeO-pyr-T acts as the most potent partial 5-HT releaser. All tryptamines elicit the head twitch response in mice, indicating potential hallucinogenic effects primarily mediated by 5-HT2A receptors, but 5-HT1A activation attenuates this response. Tryptamines producing stronger hypothermic responses via 5-HT1A tend to show lower hallucinogenic effects, highlighting opposing roles of the two receptors. Some compounds with low hallucinogenic effects remain potent 5-HT2A agonists, offering insight into non-hallucinogenic therapeutic ligands.

(2-Aminopropyl)benzo[β]thiophenes (APBTs) are novel monoamine transporter ligands that lack stimulant effects but display psychedelic-like activity in mice.

Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology March 1, 2022 Deborah Rudin, John D. Mccorvy, Grant C. Glatfelter et al. 18 citations

Derivatives of (2-aminopropyl)indole and (2-aminopropyl)benzofuran are new psychoactive substances with stimulant effects. This study characterized six isomers of the sulfur-based analog (2-aminopropyl)benzo[β]thiophene (APBT) in vitro and three isomers in vivo. APBTs inhibited monoamine reuptake and induced transporter-mediated substrate release, similar to MDMA, but did not stimulate locomotion in mice. Instead, they acted as full agonists at 5-HT2 receptor subtypes and induced head-twitch responses, indicating psychedelic-like activity. Replacing oxygen with sulfur enhanced serotonin transporter release potency and 5-HT2 receptor activity, shifting the profile toward psychedelic and entactogenic effects with minimal psychomotor stimulation, suggesting potential for drug-assisted psychotherapy.

Interaction Profiles of Central Nervous System Active Drugs at Human Organic Cation Transporters 1-3 and Human Plasma Membrane Monoamine Transporter.

International Journal of Molecular Sciences November 30, 2021 Thomas J F Angenoorth, Stevan Stankovic, Marco Niello et al. 18 citations

Many psychoactive compounds primarily interact with high-affinity monoamine transporters, but their interactions with low-affinity, high-capacity transporters like human organic cation transporters (hOCTs) and the plasma membrane monoamine transporter (hPMAT) are understudied. Using radiotracer-based uptake inhibition assays in HEK293 cells, 17 psychoactive substances were tested. Most compounds inhibited hOCT1 and hOCT2 in the low micromolar range, while few affected hOCT3 or hPMAT. Methylphenidate and ketamine selectively inhibited hOCT1 or hOCT2, respectively, and MDMA potently inhibited hOCT1, hOCT2, and hPMAT. Enantiospecific differences were observed for R- and S-α-PVP and R- and S-citalopram. These findings highlight the importance of studying drug interactions with hOCTs and hPMAT for regulating monoamine concentrations and xenobiotic clearance.

DARK Classics in Chemical Neuroscience: Aminorex Analogues

ACS Chemical Neuroscience September 30, 2018 Julian Maier, Felix P. Mayer, Simon D. Brandt et al. 15 citations

Aminorex and its analogues are psychostimulants that interact with monoamine transporters, sharing pharmacological similarities with amphetamines and cocaine. Some of these substances, originally failed pharmaceuticals, have reemerged as new psychoactive substances (NPS) for recreational use. Consumption of certain analogues, such as 4-methylaminorex and 4,4'-dimethylaminorex, has been linked to adverse events including death. This review covers the historical background, pharmacodynamic and pharmacokinetic properties, and misuse of these drugs as adulterants. It highlights the dangers of the NPS market, where users often lack knowledge of the pharmacology, potency, or identity of active ingredients.

Bioisosteric analogs of MDMA: Improving the pharmacological profile?

Journal of Neurochemistry September 1, 2024 Ana Sofia Alberto-Silva, Selina Hemmer, Hailey A. Bock et al. 10 citations

Three new chemical variants of MDMA—ODMA, TDMA, and SeDMA—show similar activity at serotonin, dopamine, and norepinephrine transporters but reduced activity at 5-HT2A/2B/2C receptors compared to MDMA. They also differ in liver metabolism, with N-demethylation as the only shared route and no phase II metabolites formed. TDMA showed faster clearance. The analogs interacted more weakly with organic cation transporters and plasma membrane monoamine transporter. These bioisosteres may offer therapeutic alternatives to MDMA with a reduced off-target profile, but further studies are needed to determine if they pose lower risks.

Editorial: Old and new psychoactive substances: Pharmacology and potential applications

Frontiers in Psychiatry January 4, 2023 Felix P. Mayer, Dino Luethi, Lorena B. Areal et al. 1 citation

Psychoactive substances have been consumed throughout human history, first from plants and fungi, then isolated compounds like cocaine, and later synthetic drugs such as LSD. Many recreational drugs also have clinical uses, e.g., amphetamines for ADHD. New psychoactive substances (NPS) have expanded the drug market and improved understanding of structure-activity relationships. Recent clinical trials are reevaluating psychedelics like psilocybin and MDMA for conditions such as depression and PTSD. This special issue includes studies on synthetic opioids, NBOMe derivatives, psilocybin's anxiolytic effects in healthy volunteers, psilocybin reducing body weight in obese rats, and reviews linking mystical experiences to symptom reduction. The collection highlights both risks and therapeutic potential of psychoactive compounds.

Correction to "Next-Generation MDMA Analogue SDMA: Pharmacological and Metabolic Insights".

ACS Chem Neurosci March 4, 2026 Nina Kastner, Núria Nadal‐gratacós, Selina Hemmer et al. correction

A correction notice clarifies that two errors in the original paper do not affect the accuracy of the results, interpretations, or conclusions. The first correction addresses a presentation issue in Table 1, confirming the data are correct. The second correction clarifies that thigmotaxis, a measure of anxiety-like behavior, was evaluated in rats given SDA or SDMA compounds. Compared to saline, only the 10 mg/kg dose of SDA significantly increased thigmotaxis, meaning the rats spent less time in the center of the arena.

Next-Generation MDMA Analogue SDMA: Pharmacological and Metabolic Insights

ACS Chemical Neuroscience December 2, 2025 Nina Kastner, Núria Nadal‐gratacós, Selina Hemmer et al.

Replacing the 1,3-benzodioxole group in MDMA (ecstasy) with a 1,3-benzoxathiole yields two analogues, SDA and SDMA, that interact with monoamine transporters similarly to MDMA but with key differences. SDA and SDMA inhibit dopamine and norepinephrine transporters more potently than MDMA and act as partial releasers at serotonin and dopamine transporters. Metabolism studies show SDA and SDMA are cleared faster, while MDMA and MDA degrade only weakly. In mice, SDMA does not produce rewarding effects, unlike MDMA, and SDA only shows a preference for the drug-paired compartment at the lowest dose. SDMA shares similar locomotor and hyperthermic profiles with MDMA, whereas SDA induces increased hyperlocomotion and more sustained hyperthermia. SDMA may be a safer candidate for further study.

The psychedelic phenethylamine 25C-NBF, a selective 5-HT2A agonist, shows psychoplastogenic properties and rapid antidepressant effects in male rodents

Molecular Psychiatry November 14, 2025 Núria Nadal‐gratacós, Pol Puigseslloses, Laura Hernández‐guzmán et al.

Three novel phenethylamine derivatives—25C-NBF, 25B-NBF, and 25I-NBF—show high affinity and selectivity for the 5-HT2A receptor, with signaling bias toward Gq over β-arrestin pathways similar to serotonin. In mice, they cause moderate head-twitch responses without affecting movement or sensorimotor gating. No rewarding or reinforcing effects were observed, and accumbal dopamine levels in rats remained unchanged. 25C-NBF promotes dendritogenesis, spinogenesis, and increased Bdnf mRNA in vitro and in vivo, reduces despair-like behavior after acute stress, and produces rapid antidepressant effects in a chronic corticosterone model of anhedonia. These findings suggest 25C-NBF may offer a fast-acting antidepressant with no abuse potential or sensorimotor deficits.

Bioisosteric analogs of MDMA with improved pharmacological profile.

bioRxiv : the preprint server for biology April 11, 2024 Ana Sofia Alberto-Silva, Selina Hemmer, Hailey A. Bock et al. preprint

Three new chemical variants of MDMA—ODMA, TDMA, and SeDMA—show similar activity at serotonin and dopamine transporters but reduced activity at serotonin 5-HT2A/2B/2C receptors, which may lower the risk of off-target side effects. They also differ from MDMA in how they are broken down by the liver, with fewer metabolic pathways and no phase II metabolites. The analogs interact more weakly with certain organic cation transporters. These findings suggest the new compounds could be promising therapeutic alternatives to MDMA for conditions like PTSD, though further research is needed to confirm whether they pose lower risks.

Salvinorin A regulates dopamine transporter function via a kappa opioid receptor and ERK1/2-dependent mechanism.

Neuropharmacology November 1, 2014 Bronwyn M Kivell, Zeljko Uzelac, Santhanalakshmi Sundaramurthy et al.

Salvinorin A (SalA), a selective κ-opioid receptor (KOR) agonist, increases dopamine transporter (DAT) activity in cells and rat striatum, which reduces dopamine signaling. This effect is mediated by KOR activation and the ERK1/2 pathway, and involves physical interaction between KOR and DAT proteins. SalA also decreases serotonin transporter activity but does not affect norepinephrine transporter activity. The enhanced dopamine transport, combined with reduced dopamine release, may contribute to the dysphoric and pro-depressant effects of SalA and other KOR agonists.