Oct 12, 2012

Wiping drug memories

What if you could wipe the memories of drugs from your mind? What if the sweet taste of relapse was no longer a fear for recovering drug users? 

Eternal sunshine of the drugless mind

Relapse back into drug use is complex. Taking into account the environmental cues that come along with using drugs. The effect of the drug is only one part. The other part being the trigger. After a while it becomes a conditioned response, making relapse an all-too-easy mechanism to fall into.

As a treatment target, relapse remains an infant, almost non-existent field. However, recently published research suggests that the memories elicited by drug cues and contexts (those environmental factors that lead to relapse) can be diminished, and hence possibly reducing or negating their impact on relapse in both animals and people addicted to drugs.

Diminishing of those drug-associated cues is brought about by pharmacologically interference. The only problem is only one of the pharmacological compounds used is suitable for human use. This means studies done in rats have yet to be mimicked in human clinical models.
However, a non-pharmacological alternative may be possible -- the “memory retrieval-extinction” behavioral procedure is used to interfere with how the cues and stimuli in addicts are formed and retrieved.

What do rats and drug users have in common?

What researchers did was to manipulate the memory processes -- essentially overwriting the original memory. The so called “extinction procedure” is commonly employed clinically to suppress conditioned responses to drug cues. What they describe is a memory retrieval-extinction procedure that decreases conditioned drug effects and drug seeking in rat models of relapse, and drug craving in abstinent heroin addicts.

What is common in all of this is a reemergence of extinguished responses -- that is to say it is not a long-lived effect. Either re-exposure to drugs, re-exposure to the drug-associated environment, or simply the passage of time can reinstate that memory.

Rats that were taught to self-administer cocaine and heroin were used in studies where drug-cues were formed. Then this bond was tested as the animals underwent “extinction training”. Essentially, the experiment induces the drug-associated condition, extinguished, then tested (and reinstated) by injecting the drug into the rats. The test is to see if the rats revert to old behaviour and recommence self-administering their drugs.

After being assessed one month later, only the group that had received the reminder and extinction training showed a reduced tendency to resume drug-seeking behaviour following exposure to either drug-associated cues or a reminder injection of cocaine or heroin.

In the study, authors were able to translate their work in rats to a human clinical setting, with detoxified heroin addicts. Three groups of patients were briefly exposed to a drug-relevant video or a control; then exposed to relevant drug-associated cues and stimuli (imagery and drug paraphernalia) to see if relapse would occur. Much like in the rats, the group that had the brief 10 minute delay between the heroin video and extinction showed a significant reduction in craving and blood pressure after presentation of drug-associated cues.

This study is one that successfully mimics a pharmacological effect in a behavioural setting, despite the ambiguousness of the mechanisms at play. And hopes to formulate a new route towards different kinds of treatment targets. An in-depth look at drug addiction and recovery can be found at Project Know and other similar websites.


PMID: 22499932 and PMID: 22499948

Written by Dr. Charles Ebikeme for The All Results Journals. 

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