"People who start drinking the earliest tend to be the most likely to develop drinking problems," said lead author Nicole L. Schramm-Sapyta, research associate in the department of pharmacology and cancer biology at Duke University Medical Center. "But we also know that not all adolescents get into trouble with alcohol and other drugs. We wanted to examine, within an adolescent population, whether these early ‘big drinkers' were different in some way ... if they had individual characteristics that were responsible for the drinking. We chose to examine novelty seeking and stress because these are two characteristics we see in some populations that develop problem drinking."
To that end, the researchers studied almost 50 male rats that were 28 days old - the equivalent of rodent adolescence. First, the rats had to navigate a maze to measure their anxiety, then had to cope with open fields and "novel objects." After some blood tests, the researchers observed how much each rat drank in special "lickometer" cages. At first, the rats got water, but then the water was replaced by alcohol for three nights, followed by a choice between the water or the alcohol for 10 straight evenings. After two nights of abstinence, the rats were again given a choice between the water or alcohol solutions in order to measure their levels of relapse.
"Rats that demonstrated a ‘taste' for alcohol after only three nights of drinking were very likely to be the biggest drinkers after longer-term exposure to alcohol," Schramm-Sapyta said.
Another important finding: Measures of novelty seeking and stress responsiveness were not related to drinking outcomes. The study has significant impacts for humans; people who drink to excess when they first begin might be more likely to become alcoholics.
"The findings suggest that early ‘big drinkers' are the people who should be targeted for alcoholism-prevention efforts," Schramm-Sapyta said. "Of course, the findings do not tell us what we should do to help those people, or why they are big drinkers so early in their experience. Future work will focus on determining other factors which can help to more accurately predict which rats will fall into that group."