A research team in Sweden has identified an enzyme whose production is turned off in nerve cells of the brain’s frontal lobe when addictive dependence develops. The deficiency in this enzyme leads to continued use of addictive substances such as alcohol despite adverse consequences. The new discovery could mean completely new possibilities for treating alcoholism and other addictions.
The enzyme, PRDM2, has previously been studied in cancer research, but researchers did not know about its function in the brain. It has long been suspected that people with alcohol dependence and other addiction illnesses have impaired function in the frontal lobes of the brain, but the underlying biological mechanisms were not known.
If the brain’s frontal function is impaired, it is difficult for us to control our impulses. A person with intact impulse control can walk past a bar on a warm day and think, 'A beer would be nice, but I cannot have one now because I have to get back to work'. An alcoholic does not have sufficient impulse control to refrain, and instead thinks 'It's hot, I'm thirsty and I need that drink'.
PRDM2 controls the expression of several genes that are necessary for effective signaling between nerve cells. When too little enzyme is produced, no effective signals are sent from the cells that are supposed to stop the impulse caused by an addiction.
Researchers found that by developing alcohol dependence in rats there was a down-regulation of PRDM2 production, which in turn led to disruption of impulse control. The rats continued to consume alcohol, even when it is unpleasant. Moreover, when the rats were subjected to stress, they were found to quickly relapse into drinking alcohol. Researchers then knocked out the production of PRDM2 in the frontal lobes of rats that were not dependent, and they again observed that impulse control was disrupted.
Now that we are beginning to understand what is happening, we hope we will also be able to intervene and contribute to developing effective treatments for addictions.