Mice have been getting drunk at the Salk Institute in La Jolla. They've been drinking alcohol as part of a study out Thursday in the journal Science, which looks at why some animals — and potentially humans — might become compulsive alcohol drinkers.
Defining compulsion
Consider an open bar. Drinks are free, so getting that second cocktail might be a no-brainer. But what if this bar becomes a cash bar? That's what Salk scientist Kay Tye has been asking. She's the lead on this study.
"Some people stop drinking, some people keep drinking, and then at some point the cash bar closes and then some people need to find another bar," says Tye.
Tye says compulsion is the habit of continuously seeking a reward despite the negative consequences, like a person paying for a drink when he's already had enough free ones. To find out why some people do this more than others, she and her team of researchers took images of brain activity in mice when they drank.
Neurological response
"We wanted to know what are these neurons doing the first time that mice experience all the way to the development of compulsive alcohol drinking?" said Tye.
Tye said researchers took images of the activity in the prefrontal cortex of the brain, where messages are sent from neurons to the brain stem.
"What we found that was really surprising was that the neural activity on this very first contact of alcohol exposure predicted whether animals would ultimately become compulsive, weeks into the future," said Tye.
When exposed to alcohol, mice with increased brain activity could stop drinking. But those with less brain activity continued to seek alcohol, despite the consequences, which were a painful shock to the foot or a yucky taste in the hooch.
More than genetic variability
But the key here, Tye said, is that all these mice are pretty similar in their genetics and the environment they grew up in.
"They’re all raised in the same cages, same lights, same food, all that stuff. So the genetic and environmental differences are very small," said Tye. That's why she says it was surprising to see so much variability.
Tye says the research shows animals and possibly humans may develop compulsive drinking habits for many reasons. Not just genetics or the environment.
"We're just understanding how the brain works at all, so we don't know yet if all the things we are finding true in mice are also going to be true in humans," said Tye.
"But, I think the idea that you can find a signal in the brain that can predict future behavior ... on the order of weeks is extremely exciting and not something I would have predicted before we did this study."
