People using Ecstasy for as little as one night are putting themselves at risk of developing Parkinson鈥檚 disease, warns a new investigation of the drug鈥檚 effects on animal brains.
The study uncovers evidence of a type of nerve damage never previously seen in monkeys or rats exposed to Ecstasy, or MDMA, and will stoke an increasingly acrimonious debate about whether it is toxic to human nerve cells.
George Ricaurte and his team at Johns Hopkins University in Baltimore, Maryland, gave up to three consecutive doses of the drug to squirrel monkeys and baboons. The doses were administered two hours apart in a bid to mimic the way some all-night clubbers use the drug.
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Weeks later, the researchers examined the animals鈥� brains and found evidence of what they call 鈥減rofound and severe鈥� damage to dopamine-producing neurons. These are the nerve cells lost in Parkinson鈥檚 disease and their healthy function is important for movement, speech and cognition.
The animals鈥� brains had abnormally low levels of both dopamine and certain 鈥渢ransporter鈥� proteins that handle this neurotransmitter. The researchers also detected signs of inflammatory damage.
鈥淭he damaging effect of MDMA, together with the decline in dopaminergic function known to occur with age, may put individuals at increased risk of developing Parkinsonism and other neuropsychiatric diseases either as young adults or later in life,鈥� the researchers write in the journal Science.
The paper also claims some people already diagnosed with early-onset Parkinson鈥檚 disease may unknowingly be victims of MDMA.
Nerve network
The link with dopamine overturns a 15-year assumption about the way MDMA interacts with the brain. Previous studies in monkeys and rats claimed the drug鈥檚 toxicity was strictly limited to serotonin-producing cells, a quite different nerve network. But in the new research these serotonin effects were mild compared with those seen with dopamine cells.
The researchers suggest the discrepancy reflects the way the drug was administered to animals in the latest study, in multiple doses given in quick succession.
But opinion is sharply divided on the relevance to human Ecstasy users. Robin Meadowcroft, director of the UK鈥檚 Parkinson鈥檚 Disease Society, told 快猫短视频 that there is no evidence early-onset Parkinson鈥檚 disease is on the increase or that former MDMA users are turning up at clinics with Parkinson鈥檚 symptoms. This is despite the fact that the drug has been widely used since the early 1980s.
鈥淚f the drug, used in large quantities, were responsible for the young-onset of Parkinson鈥檚 disease we might have expected to see some early evidence of this,鈥� says Adrian Williams, a neurologist at the University of Birmingham in the UK. Another drug from the 1980s, a synthetic heroin called MPTP, did cause Parkinsonism and was detected very quickly when users presented with severe symptoms.
Equivalent doses
The difficulty of comparing species makes it is impossible to know if the MDMA doses used in the experiment are equivalent to human doses, says Stephen Kish, a neuroanatomist at the Center for Addiction and Mental Health in Toronto.
And there are signs that they were not, say experts. The MDMA was injected rather than given orally and two of the 10 animals got so sick with hyperthermia that they died during the experiment. Overheating can strike down human users of the drug but at this frequency.
鈥淭he money would have been better spent investigating the dopamine effects in humans,鈥� says Kish.
Journal reference: Science (vol 297, p 2260)