Researchers at the University of Cambridge in England have been able to use memory-blocking chemicals to prevent rats that had become addicted to cocaine from using the drug, Scientific American reported Aug. 12.

The researchers say their findings suggest that therapeutic interventions to disrupt the recollection of specific memories associated with drug use could be developed to break the association between environmental cues and drug craving in humans. They focused in this study on experimental drugs that block NMDA-type glutamate receptors in the amygdalar region of the brain — substances that they believe could eventually be an important adjunct to behavioral therapy focusing on drug cues.

The research involved a group of caged rats that would receive cocaine after pressing a lever, and came to associate with the cocaine a light that was activated when the lever was pressed. The rats were taken out of the cages and some received the drug injections before being let back in. All of the rats would proceed to press the lever repeatedly when back in their cages, but those treated with the drugs would stop shortly after no drugs were dispensed, even though the light would still come on.

Barry Everitt, an experimental psychologist at the university, explained that the rats treated with the experimental drugs appeared to forget that the light had been associated with receiving cocaine, and this effect persisted for four weeks with administration of only one drug treatment.

Everitt said the compounds used in this study act on the same receptors as several existing products used in human medical treatment, such as the cough suppressant ingredient dextromethorphan and the Alzheimer's disease medication memantine.

Study findings were reported in the August 13 issue of the Journal of Neuroscience.