Get happy-but there may be a price to pay
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. The researchers injected subjects with a radioactive substance designed to "light up" 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. "The message is that if you're going to use MDMA, use it in moderation." Others are unconvinced. James O'Callaghan, a neuroscientist at the US Environmental Protection Agency, believes the drug fails to produce characteristic effects of nerve poisons on brain cells. "We're not saying this is a safe drug, just that there's no evidence of structural damage." David Concar
New Scientist report 97
Recent evidence concerning other drugs suggests that opiates upset the immune system significantly but the cocaine tends to boost it. Marijuana in experiments with mice and mouse immune cells appears to be damaging to the immune system, but this effect is not borne out in actual human epidemiology in which marijuana appears to be relatively non-harmful, being responsible principally for a slight increase in cancers of the head and neck region.