A new study suggests that binge-drinking during adolescence may perturb brain development at a critical time and leave lasting effects on genes and behavior that persist into adulthood.

Researchers at the University of Illinois at Chicago College of Medicine used experimental rats to investigate the effects of intermittent alcohol exposure during the adolescent stage of development. They found that on-and-off exposure to alcohol during adolescence altered the activity of genes needed for normal brain maturation. The gene alterations increased anxiety-like behaviors and preference for alcohol in adulthood.

"This may be the mechanism through which adolescent binge-drinking increases the risk for psychiatric disorders, including alcoholism, in adulthood," said Subhash Pandey, lead author of the study.

To model adolescent binge-drinking in humans, the researchers gave 28-day-old rats alcohol for two days in a row, followed by two days off, and repeated this pattern for 13 days. Some rats were followed into adulthood and observed for abnormal behaviors. They were offered both alcohol and water, and their alcohol-drinking behavior was monitored.

Rats exposed to alcohol during adolescence exhibited changes in behavior that lasted into adulthood, long after exposure to alcohol ended. They showed increased anxiety-like behaviors and drank more alcohol in adulthood.

When the researchers analyzed tissue from a part of the brain called the amygdala, they found in the exposed rats that the DNA and histones appeared to be tightly wrapped. They also found increased levels of a protein called HDAC2, which modifies histones in a way that causes DNA to be wound tighter around them.

These epigenetic changes in turn were linked to lowered expression of a gene that nerve cells need in order to form new synaptic connections. Pandey believes the lowered activity of this gene may be due to the tighter winding of its DNA. The diminished expression of the gene persisted in adulthood, even if alcohol exposure was stopped weeks before. The researchers observed diminished nerve connectivity in the amygdalae of these affected adult rats.

"Our study provides a mechanism for how binge-drinking during adolescence may lead to lasting [epigenetic] changes ... that result in increased anxiety and alcoholism in adults," Pandey said. Intermittent alcohol exposure "degrades the ability of the brain to form the connections it needs to during adolescence."

The findings are detailed in the journal Neurobiology of Disease.