3,4-Methylenedioxymethamphetamine (MDMA) neurotoxicity in rats: a reappraisal of past and present findings.
BACKGROUND
3,4-Methylenedioxymethamphetamine (MDMA) is a widely abused illicit drug. In animals, high-dose administration of MDMA produces deficits in serotonin (5-HT) neurons (e.g., depletion of forebrain 5-HT) that have been interpreted as neurotoxicity. Whether such 5-HT deficits reflect neuronal damage is a matter of ongoing debate.


OBJECTIVE
The present paper reviews four specific issues related to the hypothesis of MDMA neurotoxicity in rats: (1) the effects of MDMA on monoamine neurons, (2) the use of "interspecies scaling" to adjust MDMA doses across species, (3) the effects of MDMA on established markers of neuronal damage, and (4) functional impairments associated with MDMA-induced 5-HT depletions.


RESULTS
MDMA is a substrate for monoamine transporters, and stimulated release of 5-HT, NE, and DA mediates effects of the drug. MDMA produces neurochemical, endocrine, and behavioral actions in rats and humans at equivalent doses (e.g., 1-2 mg/kg), suggesting that there is no reason to adjust doses between these species. Typical doses of MDMA causing long-term 5-HT depletions in rats (e.g., 10-20 mg/kg) do not reliably increase markers of neurotoxic damage such as cell death, silver staining, or reactive gliosis. MDMA-induced 5-HT depletions are accompanied by a number of functional consequences including reductions in evoked 5-HT release and changes in hormone secretion. Perhaps more importantly, administration of MDMA to rats induces persistent anxiety-like behaviors in the absence of measurable 5-HT deficits.


CONCLUSIONS
MDMA-induced 5-HT depletions are not necessarily synonymous with neurotoxic damage. However, doses of MDMA which do not cause long-term 5-HT depletions can have protracted effects on behavior, suggesting even moderate doses of the drug may pose risks.
Clinical Psychopharmacology Section, Intramural Research Program (IRP), National Institute on Drug Abuse (NIDA), National Institutes of Health (NIH), 5500 Nathan Shock Drive, Baltimore, MD 21224, USA. mbaumann@intra.nida.nih.gov
Michael H
MH
Baumann
Xiaoying
X
Wang
Richard B
RB
Rothman
D000818:Animals; D001007:Anxiety / Q000139:chemically induced; D001522:Behavior, Animal / Q000187:drug effects*; D015306:Biogenic Monoamines / Q000378:metabolism*; D001921:Brain / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D004298:Dopamine / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006213:Hallucinogens / Q000633:toxicity*; D006801:Humans; D018817:N-Methyl-3,4-methylenedioxyamphetamine / Q000633:toxicity*; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D020258:Neurotoxicity Syndromes / Q000209:etiology* / Q000378:metabolism / Q000473:pathology / Q000523:psychology; D009638:Norepinephrine / Q000378:metabolism; D051381:Rats; D018570:Risk Assessment; D012701:Serotonin / Q000378:metabolism; D013045:Species Specificity
D015306:Biogenic Monoamines; D006213:Hallucinogens; D012701:Serotonin; D018817:N-Methyl-3,4-methylenedioxyamphetamine; D004298:Dopamine; D009638:Norepinephrine