The claws of addiction are hard to escape because other more salubrious rewards, like food and relationships, gradually lose their value - so goes the popular belief. But now Magalie Lenoir and Serge Ahmed have conducted studies on heroin-addicted rats that show the opposite is true - to the more highly addicted rodents, food was actually more of a beneficial distraction than it was to less addicted rats. The finding needs to be replicated in humans but has clear implications for treating addiction.
From 24 rats (see earlier), the researchers created two groups, one of which was given just one hour's access to self-administered heroin a day, and became weakly addicted. The other group had five hours' access a day, and as expected, the rats in this group became progressively more addicted, administering escalating amounts of the drug.
Next, to test the strength of the two groups' addiction, the researchers made it so the rats had to work ever harder, by pressing a lever more times, to receive a dose of heroin. This confirmed that the group given greater exposure to heroin were prepared to work harder for the drug.
Crucially, the researchers then introduced the option of food at the same time as heroin was available. To the researchers' surprise, this had the effect of reducing how hard the more strongly addicted rats were prepared to work to get heroin, whereas the more weakly affected rats were unaffected by the availability of food.
"These observations clearly showed that food consumption can act as a potent substitute for heroin use in individuals that have escalated their heroin use..." the researchers said.
The Digest asked co-researcher Serge Ahmed to comment more on the implications of this finding. "If our rat data were extrapolable to humans," he said, "then it would mean that a drug substitute exists in humans - a conclusion that should justify and encourage a search for real world drug substitutes."
Lenoir, M. & Ahmed, S.H. (2007). Supply of a nondrug substitute reduces escalated heroin consumption. Neuropsychopharmacology, Advance Online Publication.