[Representational image]Creative Commons.

Why do people give in to addiction when they know for a fact that it is harmful, and, in some cases, potentially deadly? It could all come down to the way the human brain is wired. A new research has found a mechanism in the brain that could be the reason behind addiction.

Researchers from the Linköping University, Sweden used rats to study this phenomenon. In the experiment, a number of rats were given a small dose of alcohol if they were willing to endure a short, but painful pulse of shock. Once they were trained to take as much alcohol as they wanted, they were then given an alternative.

A small lever, when pulled would give the rats sweetened water, but this time without any shocks. Almost all the rats moved away from alcohol to enjoy the free, sweet water. However, about 15 percent of the rats were found to prefer the alcohol, even if it meant enduring the shocks. Among humans, there is a similar proportion of alcohol addicts, write the researchers.

Behaviour of the rats that preferred alcohol, notes the release, was found to be quite similar to addiction in humans, like the propensity to continue consuming the addictive substance in spite of negative consequences.

We have to understand that a core feature of addiction is that you know it is going to harm you, potentially even kill you, and nevertheless something has gone wrong with the motivational control and you keep doing it," says Markus Heilig, professor at the Department of Clinical and Experimental Medicine and director of the Centre for Social and Affective Neuroscience.

Researchers went on to investigate the reason why rats get addicted and to understand the exact mechanism behind this addiction.

Scientists measured the expression of hundreds of genes in five key areas of the rats' brain. The largest differences between an addicted brain and a normal brain were found in the region of the brain called the amygdala, notes the report. This is also the region in the brain that is linked with emotional responses.

Through this experiment, scientists were able to identify molecular rearrangements in the brain that led to impulsive, and sometimes even self-destructive addiction.

Possible to switch off addiction?

In the brains of the addicted rats, one gene, in particular, is expressed at significantly lower levels, notes the report. The same gene was responsible for maintaining low levels of inhibitory signal substance around the nerve cells regulated by GAT-3, a protein that worked as a transporter.

To test just how effective this gene was, scientists simply knocked out GAT-3 from the rats that preferred sweet water.

"Decreasing the expression of the transporter had a striking effect on the behaviour of these rats. Animals that had preferred the sweet taste over alcohol reversed their preference and started choosing alcohol," says Eric Augier, lead investigator in the project.

[Representational Image]Reuters

This discovery, notes the report, could be used to improve the treatment of alcohol addiction in humans, and possibly even control alcohol dependence, says the release.

"This is one of those relatively rare times where we find an interesting change in our animal models and we find the same change in the brains of human alcoholics," said Dayne Mayfield, co-author of the new study.

The research paper, 'A molecular mechanism for choosing alcohol over an alternative reward' was first published in the journal Science.