Last year scientists created a stir with a report in Science suggesting that people who use the party drug ecstasy may damage their dopamine neurons, raising their risk of Parkinson's disease. This week they publish a retraction: Owing to a mislabeled bottle, they used the wrong drug in their experiments. The toxic effects they ascribed to ecstasy (or MDMA) were caused by a sister drug, methamphetamine, which is known to be toxic to dopamine neurons.
The lab says that it received both drugs on the same day and in identical bottles but the labels were switched. A spokesperson for the drug supplier, Research Triangle Institute (RTI) in Research Triangle Park, North Carolina, says, "we are conducting a thorough review of our procedures, even though we do not have any evidence that an error occurred at RTI."
Cognitive neuroscientist Jon Cole of the University of Liverpool, U.K., expressed doubts from the beginning about the study's implications for disease risk (ScienceNOW, 26 September 2002). "If MDMA and [Parkinson's] were linked we would be seeing hundreds, if not thousands, more young-onset Parkinson's disease cases," he says. Now, he says, "I think they should ... abandon" the quest to link the two.
Lead author George Ricaurte of Johns Hopkins University School of Medicine in Baltimore insists, however, that the retraction is not the last word. The issue of MDMA-induced dopamine neurotoxicity in primates, he says, "is [still] an open question." He also notes that the retraction doesn't affect the well-established find that MDMA is toxic to neurons that communicate via the neural messenger serotonin (and can contribute to depression as a result).
The study in question found surprisingly strong reactions--including two deaths--and "profound dopamine toxicity" in primates given injections of what the researchers thought was MDMA. The doses were roughly equivalen to what a human would get in one all-night "rave." They concluded that even brief exposure to MDMA may cause brain damage and raise a person's risk of developing Parkinson's disease, which is the result of dead dopamine neurons.
But the team's subsequent attempts to replicate the results with oral doses, from a different batch of MDMA, failed. So did a repeat of the injection approach. The researchers then became suspicious of their original drug supply. Although the bottle labeled MDMA had been discarded, they discovered that their bottle of "methamphetamine" actually contained MDMA. A check of preserved animal brains from the experiment revealed methamphetamine and not a trace of MDMA. From now on, Ricaurte says, lab members will test chemicals to be sure they are what they say they are.