Researchers from the University of Cambridge have discovered a new neural circuit that circumvents the brain region that controls decision-making processes in cocaine addicts. The study, published in the journal Nature Communications, will help to re-think therapies currently directed to modify cognitive abilities and might help prevent relapses.
Cocaine is a stimulant drug mainly used with recreational purposes, which causes euphoria, restlesness and psychosis. The molecular mechanism is based in the inhibition of dopamine, serotonin and norepinephrine reuptake, increasing these neurotransmitters concentration in the brain and allowing them to act for a longer time. High cocaine doses can rise heart rate, blood pressure and body temperature, and increase the risk of blood infections and cardiac death.
Repeated cocaine doses can lead to addiction. 40% of addicts declare feeling a craving for cocaine as the reason for relapsing. The other 60%, however, relapsed without craving: after the first doses -taken volitionally for hedonistic purposes-, these individuals used it again involuntarily. Scientists started hypothesizing about alternative explanations for cocaine relapse. In previous research, Barry Everitt’s team studied in rats the brain areas that become active upon cocaine use. They discovered that the nucleus accumbens, responsible for goal-directed behavior, is activated on the first episodes of drug use. However, after repeated consumption, brain activity moves to the dorsolateral striatum, an area with roles in habitual behavior, which would explain the inability of addicts to control drug use.
Another brain zone that becomes active after repeated drug use is the basolateral amygdala, which links stimuli with emotion, in a pavlovian manner. This impulse can be controlled with the activity in the prefrontal cortex. This would explain the 40% of relapses due to experiencing a craving for cocaine. However, it doesn’t explain the other 60%.
A new neural circuit that bypasses the prefrontal cortex
In their last study, Dr Belin and Professor Everitt studied discovered a new pathway that links the basolateral amygdala (impulse) with the dorsolateral striatum (habits), bypassing the prefrontal cortex. This would explain why some addicts are not aware of their desire to take the drug. According to the new pathway, drug use is not always a consequence of poor self-control, thus making useless current cognitive behavioral treatments for some addicts.
In a second study published in the journal Biological Psychiatry, Dr. Belin’s team discovered that N-acetylcisteine can help quit cocaine to users who have the intention to stop using it.
Source: University of Cambridge