Scientists at the Johns Hopkins School of Medicine have retracted a second study linking the drug Ecstasy to a certain type of brain damage - because once again, the wrong drug was given to lab animals.
Dr. Una D. McCann, a neuroscientist involved in both experiments, said a letter of retraction was sent yesterday to a medical journal, which she declined to identify until editors there decide how to handle the matter.
Scientists discovered the mistake after they checked lab records to see if methamphetamine - a variety of "speed" - from a mislabeled vial used in the first experiment had been used elsewhere.
"As you might imagine, we systematically went through the books to find out which, if any, of our published studies involved the same [vial]," she said last night. "We did find one, and a letter of retraction was sent out to the journal today."
The errors came about when a chemical supply company, Research Triangle International of North Carolina, switched the labels of two vials containing methamphetamine and MDMA, the active ingredient in Ecstasy.
The scientists have not found any other studies in which they mistakenly gave methamphetamine to research animals.
However, she said researchers are concerned about another possible repercussion. Because labels on two bottles were switched, it is possible that MDMA was accidentally given to animals instead of methamphetamine in another experiment. If a continued search of lab records turns up a problem of that nature, scientists might have to issue another retraction, she said.
Last week, the journal Science released a letter of retraction in which the Hopkins scientists admitted that they had accidentally given methamphetamine - rather than MDMA - to squirrel monkeys and baboons in an experiment.
That study seemed to show that MDMA damaged cells that secrete dopamine, a brain chemical needed for normal movement. Because the same type of brain damage occurs in people with Parkinson's disease, the scientists suggested that Ecstasy users might be putting themselves at risk for the devastating ailment.
The research team, led by Dr. George A. Ricaurte, suspected a problem when it was unable to replicate the results in other studies.
McCann, who along with Ricaurte has studied Ecstasy for about 20 years, declined to provide details about the second study, saying only that it involved rats and was not designed to test toxicity to dopamine cells.
The second retraction may stir up a longtime controversy over Hopkins' Ecstasy research. Critics have charged that the scientists made too much of their study results, concluding from scant evidence that the drug places users at risk for long-term brain damage.
Rick Doblin, founder of an organization that favors research into the therapeutic potential of Ecstasy, said yesterday that the researchers have been slow to scrutinize their work's validity.
"This doesn't help their credibility and goes to the whole question of what else they know," said Doblin, founder of the Multidisciplinary Association for Psychedelic Studies.
Another group of Hopkins animal studies - not called into question by the labeling problem - tied MDMA to the death of nerve cells secreting seratonin, a brain chemical that regulates mood. Loss of this chemical has been tied to depression.