Scientists who gave the club drug Ecstasy to squirrel monkeys and baboons found evidence that it produces a type of brain damage seen in people who suffer from Parkinson's disease.
In primate experiments at the Johns Hopkins School of Medicine, researchers discovered the damage after administering doses similar to those taken by young people during a single, all-night "rave" party. Destruction to nerve endings was seen in cells that secrete dopamine, a chemical needed for healthy motor function.
Dr. George A. Ricaurte, a Hopkins neurologist who has studied Ecstasy for more than a decade, cautioned that the long-term effects of Ecstasy use in humans remain uncertain. But he said the results of his latest primate experiments should give people an added reason not to take the drug.
"The most troubling implication of our findings is that young adults using Ecstasy may be increasing their risk for developing Parkinsonism, a condition similar to Parkinson's disease, as they get older," Ricaurte said.
In the experiment, scientists gave the animals three doses of Ecstasy at three-hour intervals. This simulated an increasingly popular pattern in which Ecstasy users take multiple doses to sustain their high.
Later, after the animals were killed, scientists were surprised to find that 60 percent to 80 percent of the dopamine nerve endings were destroyed in the striatum, a region where many of the cell connections are made.
"In all the animals, the lesions were seen quite consistently," Ricaurte said.
The animals did not exhibit the stiffness and tremors seen in people who suffer from Parkinson's - but this was not surprising, Ricaurte said.
Humans develop symptoms after they have lost more than 90 percent of the dopamine nerve cells. Accordingly, it is possible that people who take Ecstasy place themselves at risk for developing the disease at a relatively early age because people tend to lose dopamine as they age.
Ecstasy, the common name for the drug MDMA, became popular during the 1990s among teen-agers and young adults who enjoyed its euphoric effects and found that it loosened their inhibitions.
A survey by the U.S. Health and Human Services Department found that the number of people admitting they had used the drug at least once increased from 6.5 million in 2000 to 8.1 million last year. About 13 percent of people 18 to 25 years old said they had used the drug, compared with 3.2 percent of youths 12 to 17.
Dr. Alan I. Leshner, chief executive officer of the American Association for the Advancement of Science, said the study raises serious concerns about Ecstasy. The AAAS publishes the journal Science.
"It's an incredibly frightening study," he said. "It emphasizes that young people should not be playing Russian roulette with their own brains."
But Leshner, former director of the National Institute on Drug Abuse, cautioned that it is premature to conclude that the drug predisposes people to a condition similar to Parkinson's.
In earlier studies, Ricaurte and other scientists found that the drug damaged brain cells that secrete serotonin, a brain chemical associated with feelings of well-being. This sparked widespread warnings that people who abuse the drug, which was banned in 1985, might be setting themselves up for depression.
But the long-term effects of Ecstasy remain in dispute. Many scientists have argued that the nation would have seen an epidemic of mood disorders among Ecstasy users if the drug produced permanent damage. Researchers agree only that users experience temporary memory problems and depression - an Ecstasy "crash" - after using the drug.
Dr. Stephen Kish, an Ecstasy researcher at the University of Toronto, said the latest Hopkins study raises concerns about Ecstasy's risks.
"But we have no idea if the toxic effects in the baboons are the same in humans," Kish said, adding that scientists already knew that the drug damaged dopamine cells in rats. "I would have argued that study in another animal species was probably not warranted or important."
Ricaurte and Kish are studying Ecstasy users for signs of evidence of movement disorders. The studies involve neurological examinations as well as brain imaging tests known as PET scans, which can detect cellular changes.
"We can't be absolutely sure that the animal data will generalize to human beings," Ricaurte said. "But based on what we know so far about MDMA, that is our major concern."