Clubbers who take the "love drug" ecstasy really might be "loved up". Studies in rats suggest the drug causes a brain surge of oxytocin - the hormone that helps bond couples, as well as mothers to their babies.
Earlier research found increased oxytocin in the blood of people who had taken ecstasy. However, many drugs increase blood oxytocin without raising it in the brain - something thought necessary for any "pro-social" effects.
Iain McGregor at the University of Sydney in Australia, and his colleagues studied the effects of ecstasy in rats, which, like people, become more sociable on the drug. "It's very characteristic behaviour. They lie next to each other and chill out," McGregor says.
The team gave the rats the equivalent of two to three ecstasy tablets in an adult human and found that the drug activated oxytocin-containing neurons in an area of their brains called the hypothalamus. When they gave the rats a drug that blocked brain receptors for oxytocin, the increased sociability almost disappeared.
Why it didn't disappear entirely isn't clear. It could be that the dose of the receptor blocker was too low, or that other brain chemicals, such as dopamine, are also involved in triggering the sociable behaviour, McGregor says.
"Sensual, not sexual"
The finding ties in with reports from people on ecstasy about how they feel, McGregor points out. Rodent studies have shown a massive surge of oxytocin after orgasm in males. "It's interesting that guys on ecstasy feel more sensual than sexual," McGregor says. "It could be that raising oxytocin levels puts them in that sort of post-orgasmic state where they're actually not very good at performing sexually but they feel really good about the person they're with."
McGregor's team now plan to investigate the levels of oxytocin in rats' brains after they've taken MDMA, and to see which parts of the brain in particular are affected.
They suspect that the oxytocin release might be implicated not only in the pro-social effects of ecstasy but also in the reinforcing effects. There is much research to be done on how drugs of abuse affect oxytocin in the brain, says McGregor. "What we know at the moment could be written on the back of a postage stamp."
April 2007 by Emma Young
Journal reference: Neuroscience (DOI: 10.1016/j.neuroscience.2007.02.032)