It turns out that rats are a lot more like humans than people thought, at least when it comes to their drinking habits.
Researchers at the University of California—San Francisco recently found that a manipulation of a brain circuit in rats that triggers compulsive drinking could also be used to treat human alcoholics, but only if they want to make the change.
The scientists found that they could reduce compulsive drinking in the rats they studied by blocking a neural receptor known as NMDAR, which is present in parts of the brain that control decision-making and feelings of conflict. Compulsive drinking means a person continues to consume alcohol despite negative consequences.
For the rats, the negative consequence is simply the bitter taste of the alcohol, but for humans, it can be as substantial as losing a job or going to jail. "In a non-addict, those areas of the brain help you make the best choices you can," senior investigator F. Woodward Hopf told U.S. News.
But those areas of the brain function differently in addicts and sometimes give them the push they need to continue to drink. If people don't feel conflicted about drinking – knowing they should stop and continue to do so anyway – those areas do not play any role.
"This is what makes addiction so insidious and hard to treat," Hopf says. "It takes over normal brain functions for its own evil purpose."
That means, in order for the NMDAR blocker to work in a human, the person must want to change his or her drinking habits, Hopf says.
In their study, scientists fed the rats alcohol mixed with quinine, a bitter tasting compound that makes the drink taste like "a vodka tonic without the sugar," Hopf says.
As the rats drank, scientists noticed an increase of the receptor in two areas: the medial prefrontal cortex, which mediates a person's feeling of conflict during decision-making, and the insula, which is linked to a person's emotions and feelings of self-awareness.
The researchers then injected the rats with an agent that blocks the receptor and found that their compulsive drinking was significantly reduced. Hopf says there are already several FDA-approved drugs that can block that pathway, and that such treatment has "tremendous potential" for alcoholics.
However, any medicine would also have to be paired with extensive cognitive therapy to keep the patients engaged.
"You have to want to change, and you have to care in that moment, or the drug has nothing to work on," Hopf says.
Another way to manipulate the neural pathways is to inject the brain with a light-sensitive protein. The scientists then shine a laser light to turn off the connection between the two cortexes and a deeper part of the brain.
Although the procedure is trickier and would require an invasive surgery, Hopf says the treatment could provide a benefit for a longer period of time.
The next step, Hopf says, is working with clinical researchers to conduct a trial of the NMDAR blocker on humans, which could last several months.
"This could be the first drug that we know of where it will help you with addiction if you care and want to stop," Hopf says.