"Fine axons with small varicosities originate from the dorsal raphe nuclei, and beaded axons with large spherical varicosities arise from the median raphe nuclei. These two types of 5-HT-containing axon have different regional and laminar distributions and appear to be differentially sensitive to the neurotoxic effects of certain amphetamine derivatives, including 3,4-methylenedioxymethamphetamine (MDMA), referred to more commonly as "ecstasy." The fine axons are much more sensitive to the neurotoxic effects than the beaded axons, and the loss of fine axons lasts for months and may be permanent. Beaded axons appear to be resistant and remain unaffected following neurotoxic treatment with MDMA. This finding may be relevant to human studies, which have indicated that individuals using MDMA as a recreational drug may be exposed to dosages approximating those shown to exhibit serotonin neurotoxicity in nonhuman primates. A 26% decrease in the serotonin metabolite 5-HIAA was observed in the cerebrospinal fluid of MDMA users. This indirect evidence of a decrease in serotonin turnover in the brain perhaps reflects destruction or compromised function of this fine serotonin-containing axon system. Further studies of MDMA users seem warranted and could provide important information on the effects of selective loss of this fine axon system in humans. At present, the functional roles played by the fine and beaded axon systems and whether the functions are distinct or similar remain unclear. In serial section analysis of 5-HT terminals in the primate visual cortex, the fine and fat boutons appeared to coexist in the same axon, arguing against distinct 5-HT innervation of this brain region."
(from Ch. 10-Serotonin, "The Biochemical Basis of Neuropharmacology", 8th Ed. Cooper, Bloom and Roth)
and that's just the neurotoxicity (yeah, even pure mdma is neurotoxic), this says nothing about the somatic physiological repercussions of the drug. don't fool yourself into thinking it's completely harmless, that sort of denial died in the late 90's.
in moderation, mdma may be as toxic as a night of hard drinking; but when it gets to frequent binging, you may as well huff solvents
overheating is a somatic side-effect from MDMA itself, not just impure pills