Pubdate: Thu, 04 Oct 2001
Source: New Scientist (UK)
Copyright: New Scientist, RBI Limited 2001
Author: Emma Young


Smoking marijuana could help prevent recovering cocaine addicts relapsing, 
research on rats suggests. Dutch and US scientists deprived 
cocaine-addicted rats of the drug for 14 days and then exposed them to 
environmental cues associated with their drug-taking. Such cues often 
trigger relapse in recovering human addicts.

When the rats were also injected with a synthetic drug that blocks 
cannabinoid receptors - the same receptors targeted by the active compounds 
in marijuana - they were much less likely to seek an injection of cocaine.

"We found that in the rats exposed to environmental cues associated with 
cocaine injection in the past, or to cocaine itself, the likelihood of 
relapse was reduced by 50 to 60 per cent," says Taco de Vries, who led the 
research at Vrije University in Amsterdam and the US National Institute on 
Drug Abuse. Unpublished studies by the team on heroin-addicted rats have 
shown similar results, he told New Scientist.

Drugs to help prevent relapse in cocaine users are desperately needed, says 
de Vries. "Right now there is not much available. You can give 
anti-depressants to help with the symptoms of withdrawal but they don't 
seem to work very well."

Alcohol And Smoking

Danielle Piomelli of the University of California, Irvine agrees. "The 
finding that blockade of cannabinoid receptors prevents cue-mediated 
relapses to cocaine seeking is of obvious therapeutic significance," she 
writes in a commentary on the research in the journal Nature Medicine.

It is not clear exactly how blocking cannabinoid receptors should reduce 
the likelihood of relapse, says the team. But the cannabinoid system is 
closely linked to the dopamine system, the body's "reward" centre.

It is possible that blocking cannabinoid receptors could help people trying 
to give up alcohol, as well as heroin, cocaine and smoking, says deVries.

However, the cannabinoid system does not seem to mediate the brain's 
response to stress triggers during withdrawal, which can also cause 
relapses in drug-taking. "As with other chronic diseases, it is reasonable 
to expect that treatment of drug craving and relapse will involve the use 
of more than one drug," writes Piomelli.

Journal Reference: Nature Medicine (vol 7, p 1151)
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