It’s often said that for recovering alcoholics, one drink is too many and a thousand is not enough. The same appears to be true for those attempting to overcome a cocaine addiction, according to a new study that reveals how just a single hit of the white stuff causes a former addict’s dopamine system to revert back to its fully addicted state, even if it’s been years since their last line.
It has long been established that stimulants like cocaine inhibit proteins called dopamine transporters in a brain region called the nucleus accumbens (NAc), which forms part of the so-called reward circuit. These transporters act like tiny vacuum cleaners, sucking up excess dopamine in order to limit its excitatory effects on brain cells. When they are inhibited by cocaine, however, dopamine levels become elevated, which is why the drug causes people to get so “wired”.
Yet when someone repeatedly uses cocaine over a long period of time, they start to build up a tolerance to it, as its ability to inhibit dopamine transporters begins to decrease. As a result, the drug no longer produces the desired effect, causing people to use it more and more as they chase that elusive buzz.
Cocaine interferes with dopamine levels in the nucleus accumbens. Blamb/Shutterstock
In a new paper appearing in the Journal of Neuroscience, researchers describe how they exposed rats to cocaine-laced water for six hours a day, until the rodents became hooked on it. Using a technique called fast-scan cyclic voltammetry (FCSV), they assessed the ability of cocaine to inhibit dopamine transporters in the rats’ NAc, finding that once addiction had set in, the drug was largely incapable of producing this effect.
After 60 further days with no access to cocaine, however, the rats’ dopamine systems appeared to have returned to normal, and became completely indistinguishable from those of other rats that had never tried cocaine.