Comparative neurochemical profile of 3,4-methylenedioxymethamphetamine and its metabolite alpha-methyldopamine on key targets of MDMA neurotoxicity

• Published in: Neurochemistry international Vol. 58; no. 1; pp. 92 - 101
• Main Authors: Escubedo, E., Abad, S., Torres, I., Camarasa, J., Pubill, D.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 2011; Elsevier
• Subjects: Animals; Biological and medical sciences; Cell Membrane - metabolism; Cell Survival - drug effects; Cocaine - analogs & derivatives; Cocaine - metabolism; Deoxyepinephrine - analogs & derivatives; Deoxyepinephrine - toxicity; Dopamine - metabolism; Dopamine - physiology; Dopamine Plasma Membrane Transport Proteins - chemistry; Dopamine Plasma Membrane Transport Proteins - metabolism; Dopamine transporter; Dopamine Uptake Inhibitors - metabolism; Ecstasy; Fundamental and applied biological sciences. Psychology; In Vitro Techniques; Male; MDMA; Methyldopamine; Monoamine Oxidase - metabolism; Monoamine Oxidase Inhibitors - pharmacology; N-Methyl-3,4-methylenedioxyamphetamine - toxicity; Neurotoxicity Syndromes - metabolism; Paroxetine - metabolism; PC12 Cells; Protein Conformation - drug effects; Rats; Rats, Sprague-Dawley; Receptors, Nicotinic - drug effects; Serotonin - metabolism; Serotonin Plasma Membrane Transport Proteins - chemistry; Serotonin Plasma Membrane Transport Proteins - metabolism; Serotonin transporter; Serotonin Uptake Inhibitors - metabolism; Synaptosomes - drug effects; Synaptosomes - metabolism; Vertebrates: nervous system and sense organs; Ecstasy; Methyldopamine; Dopamine transporter; Serotonin transporter; MDMA; Neurotoxicity; Dopamine; Metabolite; Neurotransmitter; Drug of abuse; Catecholamine; Carrier protein
• ISSN: 0197-0186; 1872-9754
• DOI: 10.1016/j.neuint.2010.11.001

▶ Methyldopamine constitutes the major first line of metabolites from MDMA and MDA. ▶ Methyldopamine induces a persistent change of the dopamine transporter conformation. ▶ Methyldopamine competes with serotonin for its uptake. ▶ Methyldopamine can reduce the neurotoxicity induced by MDMA at serotonergic neurons. ▶ Methyldopamine seems to potentiate the dopaminergic lesion induced by MDMA.
The neurotoxicity of MDMA or “Ecstasy” in rats is selectively serotonergic, while in mice it is both dopaminergic and serotonergic. MDMA metabolism may play a key role in this neurotoxicity. The function of serotonin and dopamine transporter and the effect of MDMA and its metabolites on them are essential to understand MDMA neurotoxicity. The aim of the present study was to investigate and compare the effects of MDMA and its metabolite alpha-methyldopamine (MeDA) on several molecular targets, mainly the dopamine and serotonin transporter functionality, to provide evidence for the role of this metabolite in the neurotoxicity of MDMA in rodents.
MeDA had no affinity for the serotonin transporter but competed with serotonin for its uptake. It had no persistent effects on the functionalism of the serotonin transporter, in contrast to the effect of MDMA. Moreover, MeDA inhibited the uptake of dopamine into the serotonergic terminal and also MAO
B activity.
MeDA inhibited dopamine uptake with a lower IC
50 value than MDMA. After drug washout, the inhibition by MeDA persisted while that of MDMA was significantly reduced. The effect of MDMA on the dopamine transporter is related with dopamine release from vesicular stores, as this inhibition disappeared in reserpine-treated animals. However, the effect of MeDA seems to be a persistent conformational change of this transporter.
Moreover, in contrast with MDMA, MeDA did not show affinity for nicotinic receptors, so no effects of MeDA derived from these interactions can be expected. The metabolite reduced cell viability at lower concentrations than MDMA. Apoptosis plays a key role in MDMA induced cellular toxicity but necrosis is the major process involved in MeDA cytotoxicity.
We conclude that MeDA could protect against the serotonergic lesion induced by MDMA but potentiate the dopaminergic lesion as a result of the persistent blockade of the dopamine transporter induced this metabolite.