Halting memories could prevent drug-addict relapse
13 August 2008
A new approach to preventing drug-addicts from relapsing into addiction could be on the horizon. Researchers led by Professor Barry Everitt of the University of Cambridge have shown that disrupting the brain’s ability to retrieve memories associated with drug taking could make it possible to prevent relapse. In a paper published in the Journal of Neuroscience, the scientists describe how drug-seeking behaviour in rats was reduced by blocking the receptors in the brain involved in recall of drug-associated memories. The Medical Research Council provided funding for the research.
Environmental cues can prompt drug abusers to recall memories of past drug use that may lead to relapse. In this study, the Cambridge team has shown that disrupting memories during reconsolidation reduced future drug-seeking behaviour in rats, even in animals with extensive drug taking experience.
The receptor targeted, known as a NMDA subtype glutamate receptor, is part of a larger group of receptors called NMDAR important in learning and memory.
Memories are not immune to change and the findings build on past research that has demonstrated how they can be altered. When not in use, memories are stable. But when they are thought about again they can become unstable, a memory might be reinforced or weakened; the process by which they become re-stabilised is called memory reconsolidation.
The rats were trained to associate a light switching on with cocaine. Then the researchers reactivated the memory of the association by exposing the rats to the light without the cocaine. Later, the rats continued to perform behaviors that turned on the light, or learned to perform new behaviors, in an effort to get more cocaine.
When the rats were given a chemical that interfered with the action of the NMDA-subtype glutamate receptor prior to the reactivation session, the rats subsequently showed reduced cocaine-seeking behaviour. A single treatment was found to reduce or in some cases stop drug-seeking behaviour for up to one month.
In contrast, blocking NMDA-type glutamate receptors after or without the reactivation session had no effect on subsequent drug-seeking. These findings suggest that drug-associated memories and the drive to abuse drugs may be disrupted by blocking NMDA receptors during, but not after reconsolidation.
Previous efforts to expose human addicts to drug-associated cues in the absence of drug reward have been ineffective at preventing relapse. The current findings suggest that the combination of this existing therapy with properly timed use of NMDA receptor inhibitors may help addicts abstain from drugs.
Professor Barry Everitt said:
“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. Such treatments would be expected to diminish the effects of those memories in the future and help individuals resist relapse and maintain their abstinence.”
Original research paper: Intra-Amygdala and Systemic Antagonism of NMDA Receptors Prevents the Reconsolidation of Drug-associated Memory and Impairs Subsequently Both Novel and Previously Acquired Drug-Seeking Behaviours is published in the Journal of Neuroscience.
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