Experiments indicate that both moderate and high dose or rapidly repeated MDMA exposure may lead to long-lasting changes in neurons that make serotonin. Serotonergic changes have been demonstrated experimentally in the brains of all mammalian species studied, with most studies involving rats. In these studies, the brains of animals who are given high or repeated doses of MDMA show long-term decreases in all measures of serotonergic functioning, including concentrations of serotonin, tryptophan hydroxylase, and binding of the serotonin transporter protein. Although measures of serotonin are decreased, there are no decreases in the number of cells in the dorsal raphe, which indicates that the serotonin neurons have not died. Limited studies attempting to stain and photograph serotonergic axons shortly after high-dose MDMA exposure have reported that axons appear swollen and misshapen, as if they might be degenerating. However, few studies have attempted to stain and examine axons and with the measures commonly used in MDMA studies it is difficult or impossible to distinguish axon loss from decreases in production of markers of serotonin.[41][42]I don't think anybody disputes that MDMA use depletes serotonin. That's obvious to anyone that does it more than a few times. The question is whether it recovers, how long it takes, and how much loss there is.
Animal studies show that there is recovery of serotonergic markers. However, if axons are actually regrowing, there is no assurance that they will reform their original connections. While rats show extensive recovery that sometimes appears complete [43][44], some primate studies show evidence of lasting alterations in serotonergic measures. Human studies, discussed below, show recovery, but these studies use indirect measures that may lack sensitivity for detecting subtle changes.
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posted by empath at 12:37 AM on July 24, 2010