Cocaine Addiction, and How it Affects the Brain

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Addiction to drugs and alcohol have devastating consequences costing people their families, homes, jobs and even lives. Yet in the face of this many addicts continue to use. How can someone choose to continue using a drug knowing what s at stake?

The answer to this question is not simple. It is known that the release of dopamine (the happy chemical) in the brain makes people feel good, and the lack of it encourages more use to chase that high. At some point the transition occurs from voluntary to compulsive use. Quitting is often unsuccessful. Four out of 10 times relapses are caused by craving the drug, while the other six times relapses occur for reasons other than craving.

An article published in Nature Communications offers an alternative explanation for addictive behavior. The progression of drug use from volitional to habitual use involves a shift of activity from one area of the brain to another. Initially addiction involves the nucleus accumbens, or what is referred to as the brain s pleasure center it's responsible for motivation, pleasure, reward and reinforcement learning.

In this study, researchers found that extended exposure of rats to cocaine shifted activity from the pleasure center to the dorsolateral striatum an area of the brain responsible for habitual behavior. This means that there is a move from self-controlled behavior to an automatic, habitual-type behavior.

Chronic exposure to a drug also alters another part of the brain called the basolateral amygdala (BLA). This region is where pleasurable memories are stored. Relocation of cognitive function from the responsible part of the brain to the BLA enslaves it to a part that links the stimulus (cocaine) to happy emotions.

This means that with addicts the pre-frontal cortex, which is responsible for cognitive behavior and decision-making, is circumvented. A new pathway linking memory/emotion to habitual behavior is then created.

We ve always assumed that addiction occurs through failure of our self-control, but now we know this is not necessarily the case, says Dr. Belin-Rauscent, one of the paper s authors. We ve found a back door directly to habitual behavior.

This is important because drug rehabilitation often involves cognitive-behavioral therapy, and if the cognitive area of the brain is bypassed then this therapy may not make much impact.

Drug addiction is mainly viewed as a psychiatric disorder, with treatments such as cognitive behavioural therapy focused on restoring the ability of the prefrontal cortex to control the otherwise maladaptive drug use," Dr. Belin adds. "But we ve shown that the prefrontal cortex is not always aware of what is happening, suggesting these treatments may not always be effective.

Another study, published by the same authors in the journal, Biological Psychiatry, build on a previously studied medication that is commonly used to treat people with acetaminophen overdose. N-acetylcysteine (NAC) has been shown in rat studies to prevent drug relapse but this was not observed in human clinical trials.

The investigators treated cocaine-addicted rats with NAC and punished their cocaine use with electric foot shocks, to determine whether a negative outcome would take precedence over using. What they found was that in comparison to placebo, the rats receiving NAC were more sensitive to receiving shocks and abstaining from cocaine. When the punishment was discontinued the rate of relapse was much lower in NAC-treated rats. They concluded that in the face of adverse consequences, treatment with NAC restored some control over cocaine use.

In human trials while NAC did not help subjects stop using cocaine, it did help those, motivated to stop their use, to maintain abstinence.

According to the authors it seems that NAC is able to rewire the brain so that it is able to adapt and learn new skills a phenomenon known as plasticity.

About 40-60 percent of drug addicts relapse and addiction will always be tough to treat. Hopefully better understanding of the neurochemical processes involving addiction as well as continuing efforts to curb relapse will help those individuals to stay sober.