Binge drinking can harm brains within few months of intermittent access to alcohol, states study.
The researchers linked the rats' impairment to a small group of neurons that inhibit "executive control" functions in the prefrontal cortex of the brain. These neurons were unusually active in the periods between drinking binges—and the more active they were, the more the rats drank when they next had access to alcohol. The finding, if confirmed in studies of humans, could lead to better treatments, preventive approaches and diagnostic tests for problem drinking and possibly other addiction-like behaviors.
"We suspect that this very early adaptation of the brain to intermittent alcohol use helps drive the transition from ordinary social drinking to binge drinking and dependence," said Olivier George, PhD, senior staff scientist at TSRI and lead author of the study.
"This research is giving us a window into the early development of the addiction process," said the study's senior author, George F. Koob, PhD, chairman of the Committee on the Neurobiology of Addictive Disorders and co-director of the Pearson Center for Alcoholism and Addiction Research at TSRI.
The new study appears online ahead of print in the Early Edition of the Proceedings of the National Academy of Sciences
the week of October 15, 2012.
Binge Drinking Versus Consuming a Little Every Day
Scientists have long known that alcohol dependence and other addictions feature striking changes in the brain. These include an overactivity of stress-related circuits and a weakening of the prefrontal executive control circuits that normally act as a brake on emotional reactions and impulsive behaviors. What hasn't been understood is the sequence of neural events by which these changes come about.
To find out more about these early events, Dr. George set up a study of rats that had access to alcohol only three days per week (Tuesday, Thursday and Saturday). Previous research had shown that rats in this intermittent-access situation start out as modest drinkers, but eventually turn into binge drinkers, consuming even more than rats that have 24/7 access to alcohol. "It's like a lot of things in life that the brain perceives as good—if it loses access to it, you feel bad, you get into a negative emotional state, say a little bit frustrated, and so you take more the next time you have access," said Dr. George.
The team confirmed that the group of rats with intermittent access drank markedly more alcohol, on average, than those with continuous access after only six weeks. In tests conducted a few weeks later, during "dry" intervals between drinking bouts, the binge drinking rats scored poorly on measures of working memory, an essential element of executive control. Tests of their brain tissue also revealed that during these withdrawal periods—when the animals would have been expected to be craving alcohol—the prefrontal cortex seemed relatively disconnected from the structures it is meant to regulate, such as the emotion-related amygdala.
"We normally see such changes in the brains of humans or other animals that are highly dependent on alcohol, but here we found these changes in the rats after only a few months of intermittent alcohol use," said Dr. George.