What Does Meth Research Have to Do With Addiction and Autism Treatments? It's Oxytocin
The hormone oxytocin — known as the "love drug" or "cuddle chemical" — plays an important role in pair-bonding, child-rearing and social behavior. Now researchers are discovering that it could also help explain the effects of a popular party drug, and may be involved in some potential treatments for autism and addiction.
Here's a rundown of some of the latest research findings:
1. The ecstasy–oxytocin link. Researchers have found that the loved-up effects of ecstasy (MDMA) are due at least in part to oxytocin. "Administration of MDMA increases plasma oxytocin levels in humans," says Gillinder Bedi, Columbia University assistant professor of clinical psychology and lead author of new research on the effects of MDMA and methamphetamine, which I reported previously here.
The oxytocin–MDMA link has also been shown in rats, according to Iain McGregor, professor of psychopharmacology at the University of Sydney. "We were able to get rid of a big part of the social behavior induced by MDMA [by blocking oxytocin]," he says. "What was striking was the big reduction in social [facilitation] — but it was not a complete abolition."
2. Using oxytocin to battle addiction? In Bedi's recent study, he found that methamphetamine and MDMA were surprisingly alike in terms of their social effects (surprising, because users on meth are typically thought of as cold and compulsive, rather than warm and fuzzy like users of ecstasy), at least when the methamphetamine was given orally at low doses. It turns out, however, that oxytocin is not the common denominator between the two drugs — MDMA may increase oxytocin, while methamphetamine may not affect it directly.
In previous rat studies, researchers have found that the release of oxytocin is not involved in the high of amphetamine (whose effects are more similar to those of methamphetamine than MDMA's are) — and that blocking the hormone had no effect on rats' desire for the drug. Conversely, blocking oxytocin did decrease rats' interest in MDMA, suggesting that the hormone may be involved in ecstasy's "high."
But, interestingly, increasing oxytocin may reduce desire for meth. McGregor found that giving rats oxytocin made them lose interest in taking methamphetamine. "Much to our surprise and delight, we were able to basically eliminate meth self-administration, which is extremely vigorous in rats," he says. "If you don't limit them, they can overdose. It was quite interesting."
As a result of that research, McGregor and his colleagues are now testing intranasal oxytocin to help reduce addiction in alcoholics and heavy pot smokers. "We're in very early stages of clinical trials," he says.
3. Why oxytocin may help autistic people. Unlike meth and amphetamine, MDMA isn't particularly addictive. Over time users typically take MDMA less frequently, not more, as it tends to stop having pleasant effects. Could oxytocin be involved in the difference?
"One idea that we chucked around is that there are two parallel systems in the brain — one to do with desire for things and objects, the other tilted toward animate objects, friends, family, maybe pets," says McGregor.
Both systems clearly involve the neurotransmitter dopamine, which has long been linked with desire — including addictive desire — and the pleasures involved in anticipation and drive.
"Maybe when you get high levels of oxytocin, plus high levels of dopamine, you have a motivational situation where you are strongly oriented toward [people]," McGregor says. "Maybe when it's only dopamine, you're oriented toward objects."
The former situation would describe the MDMA user, who is not compulsively driven to take more ecstasy but who does want to cuddle and be social while high. In the latter situation, you have high-dose methamphetamine users — compulsively driven not only to take more meth, but to engage in repetitive behaviors with objects like scrubbing the floor or organizing collections.
If those characteristics sound vaguely reminiscent of autism, you'd be right. The findings on oxytocin may well lead to some new treatments for autism, McGregor suggests, given that autistic people have difficulty making the oxytocin-driven connection between people and pleasure. The drug baclofen, which is, in various forms, being tested for the treatment of alcoholism, other addictions and autism, has in fact been shown to affect oxytocin. "We published a paper last year showing that baclofen strongly activated oxytocin in the rat brain," says McGregor. And oxytocin itself is also being studied as a treatment for autism.
Sometimes the intricate interconnections of science — in this journalist's experience — can be overwhelming. Who knew that a new study on methamphetamine and MDMA would connect to experimental treatments for both autism and addiction?
December 21, 2010