Like most addictive substances, alcohol is known to trigger the production of dopamine, a chemical messenger in the brain that stimulates the “reward center.” Scientists have found evidence that explains why it is so hard for alcoholics to stop drinking.
Previous studies have shown that addiction reduces the production of dopamine which means that alcoholics need to drink more to experience a “buzz.” New findings from the Proceedings of the National Academy of Sciences suggest that when an alcoholic stops drinking, the brain’s ability to use dopamine changes, completely rewiring the reward system.
Known as a hypodopaminergic state, decreased dopamine levels are not clearly understood during a period of abstinence. To gain a better understanding, researchers started by examining the brain tissue of deceased alcoholics.
They found that these “addicted” brains had fewer dopamine receptors. Less receptors means less effectiveness of dopamine, which means greater amounts of alcohol are needed to produce a satisfying effect. They also found that these brains had fewer dopamine transporter sites. Dopamine transporter sites allow unused dopamine to be reabsorbed and reused. Without these the brain is less efficient at using dopamine.
They did note that there was not a decrease in D2 receptor sites that bind with dopamine to inhibit rather than excite the neurons. Basically everything points to alcohol decreasing the reward center of the brain, leading alcoholics to continually find stimulation through booze, a negative feedback loop.
The authors then shifted their focus to why this happens and the events that lead up to it. They tracked the dopamine levels in the brains of alcohol-dependent rats that they deprived of alcohol for weeks.
The first six days were exactly as expected. Acute alcohol withdrawal creates a the state of hypodopaminergic, but the availability of dopamine receptor sites and transporter sites were normal.
After three weeks, the rats brains started to look like those of the deceased alcoholics with elevated dopamine levels but falling number of receptor and transporter sites. The elevated dopamine was due to the fact that the brain didn’t have the receptors to use the dopamine or the transporters to reabsorb it. It was just sitting there useless.
The study authors concluded that acute alcohol withdrawal is associated with a hypodopaminergic state, prolonged abstinence from alcohol leads to a hyperdopaminergic state. Both of which are signs of dysfunctional reward system in the brain and increase the person’s risk for relapse.
