^ abcdAguilar MA, García-Pardo MP, Parrott AC (January 2020). "Of mice and men on MDMA: A translational comparison of the neuropsychobiological effects of 3,4-methylenedioxymethamphetamine ('Ecstasy')". Brain Research. 1727: 146556. doi:10.1016/j.brainres.2019.146556. PMID31734398. The metabolites of MDMA are 3,4-methylenedioxyamphetamine (MDA), 3,4-dihydroxymethamphetamine (HHMA), α-methyldopamine (α-MeDA), N-methyl-αmethyldopamine (N-Me-α-MeDA) and 5-(glutathion-S-yl)-α-methyldopamine [5-(GSH)-α-MeDA]. There is a substantial hepatic metabolism of MDMA, since levels of MDA and HMMA exceed that of MDMA in plasma. [...] The metabolites of MDMA, as well as those of DA, enhance the formation of quinoproteins and alter synaptosomal glutathione status, suggesting the role of these metabolites in the neurotoxicity induced by MDMA (Barbosa et al., 2012). However, the major reactive metabolite of MDMA, HHMA, does not contribute to acute or long-term MDMA-induced DA depletion, since peripheral administration of this metabolite fails to alter striatal DA. Furthermore, HHMA has been detected in the brain following its systemic injection, but not after systemic MDMA administration (Escobedo et al., 2005).
^ abSeiden LS, Sabol KE (1996). "Methamphetamine and Methylenedioxymethamphetamine Neurotoxicity: Possible Mechanisms of Cell Destruction". In Majewska MD (ed.). Neurotoxicity and Neuropathology Associated with Cocaine Abuse. NIDA research monograph. U.S. Department of Health and Human Services, National Institutes of Health, National Institute on Drug Abuse. pp. 251–276. Retrieved 30 September 2024. Steele and colleagues (1991) found that alpha-methylepinine, a metabolite of MDMA formed by demethylenation, failed to damage the 5-HT system in rats.
^ abSchmitt KC, Reith ME (February 2010). "Regulation of the dopamine transporter: aspects relevant to psychostimulant drugs of abuse". Annals of the New York Academy of Sciences. 1187: 316–340. doi:10.1111/j.1749-6632.2009.05148.x. PMID20201860. In humans, MDA and MDMA are largely metabolized via demethylenation by the hepatic CYP2D6 enzyme to the respective 3,4-dihydroxyamphetamine species (α-methyldopamine and α,N-dimethyldopamine).135 In recent years, several investigators have revealed that—much like dopamine—these catechol species readily undergo oxidation to semiquinone and quinone species that can form neurotoxic thioether compounds in vivo.136,137 [...] In particular, the dopaminoquinone-like metabolite of MDA/MDMA can undergo conjugation with the cysteinyl thiol moiety of the endogenous reductant glutathione (GSH) to form the thioether 5-(glutathionyl)-α-methyldopamine (5-(GSH)-αMeDA) or its N-methyl analogue.136 In the central nervous system, the 5-(glutathionyl)-thioethers are ultimately metabolized via the mercapturic acid pathway to form 5-(N-acetyl-cysteinyl)-α-methyldopamine (5-(NAC)-αMeDA) and its N-methyl analogue (5-(NAC)-α,N-diMeDA). The structural formulae of these metabolites and their relative potencies as neurotoxins are displayed in Figure 2. The thioether metabolites are potent serotonergic neurotoxins that can induce a dose-dependent increase in ROS formation and cause caspase-3–mediated apoptosis in cultured cortical neurons.137 Moreover, direct intrastriatal administration of pure 5-(NAC)-α,N-diMeDA in rats fully recapitulates the serotonergic toxicity observed with systemic high-dose MDMA.136 These thioethers are detectable in the rat brain after systemic administration of a high-dose neurotoxic regimen of MDMA—repeated dosing leads to significant accumulation due to a nonlinear increase in elimination half-life.139
^Baggott M, Mendelson J (2001). "Does MDMA Cause Brain Damage?". In Holland J (ed.). Ecstasy: The Complete Guide: A Comprehensive Look at the Risks and Benefits of MDMA. Inner Traditions/Bear. pp. 110–145, 396–404. ISBN978-0-89281-857-0. Retrieved 24 November 2024. While a single injection of MDMA into the brain (intracerebroventricularly) had no effect on TPH activity, slow infusion of 1 mg/kg MDMA into the brain over 1 hr produced enough oxidative stress to acutely reduce TPH activity (Schmidt and Taylor 1988). The acute decrease in TPH activity is an early effect of MDMA and can be measured at post 15 min (Stone et al. 1989b). TPH inactivation can also be produced by non-neurotoxic MDMA doses (Schmidt and Taylor 1988; Stone et al. 1989a; Stone et al. 1989b). It therefore appears that MDMA rapidly induces oxidative stress but only produces neurotoxicity when endogenous free radical scavenging systems are overwhelmed.
