One of the drivers of alcohol and drug addiction is the powerful and enduring memories of the triggers - the people, places, sights and sounds that lead up to and surround episodes of substance use. Encounters with such powerful cues are recognized as primary reasons for relapse.
Now, a team that successfully stopped cocaine and alcohol addiction in rats using a drug already approved for the treatment of high blood pressure, suggests the compound - called isradipine - may prevent relapse by erasing unconscious memories of the triggers underlying addiction.
The researchers, from The University of Texas at Austin, report their findings in the journal Molecular Psychiatry.
Before the 1970s, many scientists believed addiction was a physical craving that could be overcome with willpower.
Now, more and more regard addiction as a brain rewiring problem, and that relapse during recovery can be triggered by encounters with environmental cues that have become strongly associated with the addictive substance.
Russian physiologist Ivan Pavlov showed that if you ring a bell every time you feed a dog, eventually the sound of the bell on its own - without the food - will cause the dog to salivate.
For the study, the team - led by Hitoshi Morikawa, associate professor of neuroscience - focused on brain circuits known to be involved in learning, memory and reward, which are thought to become rewired in addiction, forming powerful memories of drug-related cues.
They trained rats to associate either a black or white room with cocaine or alcohol as they became addicted to the substances.
After the animals had become addicted, the researchers offered them the choice of either entering the black or the white room. The rats nearly always chose the room they associated with the addictive substance.
Isradipine erased memories that associated a cue with the addictive substance
Then, the researchers gave some of the addicted rats a high dose of isradipine just before presenting them with a choice of rooms. On the day they were treated, the rats still chose the room linked to their substance use. But on subsequent days, they no longer showed a particular preference. This did not happen in the untreated group.
"The isradipine erased memories that led them to associate a certain room with cocaine or alcohol," explains Prof. Morikawa.
Isradipine reduces high blood pressure by blocking calcium channels in the heart and blood vessels. However, these calcium channels are also present in the brain, and the researchers suggest blocking them with isradipine may have had the effect of rewiring the circuits that underlie memories of addiction-associated cues - like the colors of the cocaine and alcohol rooms in the rat experiments.
A drug that targets the triggers that lead up to addiction is likely to be more effective than the drugs currently used to prevent people from experiencing the euphoria that accompanies addictive drug use, says Prof. Morikawa. He explains:
"Addicts show up to the rehab center already addicted. Many addicts want to quit, but their brains are already conditioned. This drug might help the addicted brain become de-addicted."
Isradipine is already approved by the US Food and Drug Administration (FDA) as safe for human use so should not take as long to complete clinical trials as a new, unapproved drug.
However, as isradipine is designed to lower blood pressure, it may be necessary to pair it with another drug that stops blood pressure getting too low. This could be a challenge in getting the drug through trials as a treatment for addiction.
Meanwhile, Medical News Today recently learned that illicit drug taking in the workplace appears to be on the rise in the US. Data from millions of workplace urine tests suggest the proportion of American workers testing positive for illicit drugs - such as marijuana, cocaine and methamphetamine - is nearing 5%, in a second annual increase.