Blocking the brain's ability to recall drug experiences could prevent relapses in addicts, according to a new study published in the Journal of Neuroscience. By blocking the NMDA-type glutamate receptor in the brains of rats - crucial for learning and memory - researchers reduced the rodents' drug-seeking behaviors. The results could lead to new strategies to treat human drug addicts.

Previous studies had shown that even long-held memories can be altered as they are recalled; over time, memories become unstable, weakened or reinforced as part of a process scientists call reconsolidation.

The study's authors, professors Amy Milton, Barry Everitt and colleagues at the University of Cambridge, showed that disrupting memories of drug-associated cues during the reconsolidation process lessened drug-seeking behavior, even in rats with a long history of drug taking.

The rats were trained to correlate the switching on of a light with an infusion of cocaine. When exposed to light without the shot of cocaine, the rats' memory was reactivated; accordingly, their actions indicated a desire to turn on the light in an effort to get more cocaine.

However, when the researchers dosed the rats with a drug that interfered with the NMDA-type glutamate receptor prior to - but not after -- reactivation, the rats didn't display as much cocaine-seeking behavior. No matter how the drug was administered, as long as it came before reactivation, the rats didn't show enthusiasm for cocaine - in some cases, for up to a month.

"The results suggest that efforts should be made to develop drugs that could be given in a controlled clinical or treatment environment in which addicts would have their most potent drug memories reactivated," Everitt said. "Such treatments would be expected to diminish the effects of those memories in the future and help individuals resist relapse and maintain their abstinence."

The findings suggest that the blending of this existing therapy with properly timed use of NMDA receptor inhibitors may assist addicts in refraining from drugs. In the United States, the Food and Drug Administration has already approved several NMDA receptor inhibitors, including the cough suppressant dextramethorphan and the Alzheimer's disease drug memantine.