BRAIN scans of drug users have yielded the first direct evidence that
ecstasy, or MDMA, can trigger long-lasting changes in the human brain. Several
studies have suggested that the drug can cause memory impairment and depression
(This Week, 21 June, p 4).
A team led by George Ricaurte at Johns Hopkins University in Baltimore used
positron emission tomography to scan the brains of 14 MDMA users. For
comparison, they also scanned the brains of people who had used drugs such as
cocaine, heroin and marijuana but had never taken MDMA.
A key difference came to light when the researchers looked at synapses that
specialise in releasing the neurotransmitter serotonin. The brain has millions
of these nerve junctions, which are involved in a vast range of functions and
behaviours, including the control of moods.
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The researchers injected subjects with a radioactive substance designed to
鈥渓ight up鈥� in the presence of healthy serotonin synapses. The substance sticks
to a protein that transports serotonin across cell membranes.
The control subjects had normal levels of the transporter protein, but the
MDMA users had deficiencies in all brain regions. Team member Una McCann
believes the scans provide clear evidence that MDMA can damage serotonin
synapses in humans. 鈥淭he message is that if you鈥檙e going to use MDMA, use it in
尘辞诲别谤补迟颈辞苍.鈥�
Others are unconvinced. James O鈥機allaghan, a neuroscientist at the US
Environmental Protection Agency, believes the drug fails to produce
characteristic effects of nerve poisons on brain cells. 鈥淲e鈥檙e not saying this
is a safe drug, just that there鈥檚 no evidence of structural damage.鈥�