Scientists in the US studying alcohol behaviour in rats have discovered a link between early drinking patterns during adolescence and a tendency toward heavy drinking in adulthood. They found this was a separate predictor to novelty seeking, anxiety and stress, which are also thought to contribute to vulnerability in teenagers who start drinking.

The study is the work of Dr Nicole L. Schramm-Sapyta, associate researcher with the Department of Pharmacology and Cancer Biology at Duke University School of Medicine in Durham, North Carolina and colleagues, and is published in the May issue of Alcoholism: Clinical and Experimental Research.

Schramm-Sapyta said their research suggested that:

“Drinking patterns in adolescents may be set after only a few exposures to alcohol.”

“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,” she added.

In their background information the authors related that alcohol abuse disorders emerge over time as alcohol is consumed repeatedly, but not all drinkers go on to develop them. Being a novelty seeking teenager going through stressful times appears to fit the characteristic profile of the most vulnerable individuals.

Also, how a young person responds to their first drink influences future drinking habits, said the authors, who for this study examined behaviours and hormones in adolescent male rats (28 days old) before being exposed to ethanol (the type of alcohol found in alcoholic drinks), and then observed to see which rats were most likely to have high drinking patterns in adulthood.

The rats were tested every day for anxiety (using an elevated maze) and response to novelty (for instance by giving them new objects or territory to explore). Their circulating levels of the stress hormone corticosterone were also measured after mild restraint and after the maze exercise.

Every day after these tests, the rats were placed from 5 pm to 9 am in cages where their fluid consumption could be measured using “lickometers”. At first they were habituated to drinking only water; then for three nights, the rats only had alcohol to drink (10 per cent ethanol by volume). Then for 10 days afterwards, they could choose either water or 8 per cent alcohol.

Then, after 2 nights of no alcohol at all, they were placed in cages where they could choose either 8 per cent ethanol or water, in order to assess their relapse behaviour (how they returned to alcohol in response to deprivation).

The results showed that:

  • Ethanol intake on the third day of forced consumption was significantly linked to ethanol intake on days 8 to 10 of the choice phase.
  • Consumption during the choice phase was in turn significantly linked to relapse-like consumption.
  • Preference for alcohol in the choice phase was also signficantly linked to early consumption.
  • Novel object exploration, open territory activity, performance in the maze test, initial water consumption, and hormone levels did not signficantly predict consumption stimulated by deprivation.

The researchers concluded that the results suggested:

“Consumption during early exposure to ethanol establishes a pattern leading to development of increased alcohol consumption and preference in adolescent male rats.”

They also said that the results:

“Represent an animal model of the well-described observation that humans who consume large quantities of ethanol during early exposure are the most likely to repeat heavy drinking behavior.”

And furthermore:

“Early consumption is distinct from novelty seeking, anxiety, and stress hormone levels which are also thought to contribute to vulnerability to alcoholism.”

Sinced rats are mammals with a genome not too dissimilar from that of humans, it is possible, with caution, to “extrapolate from rodents to human”, said Schramm-Sapyta.

It would be unethical to do these kinds of experiments on human adolescents, so rats are the next best thing.

Schramm-Sapyta said that:

“The findings suggest that early ‘big drinkers’ are the people who should be targeted for alcoholism-prevention efforts.”

“Early Ethanol Consumption Predicts Relapse-Like Behavior in Adolescent Male Rats.”
Nicole L. Schramm-Sapyta, Megan A. Kingsley, Amir H. Rezvani, Kiayia Propst, H. Scott Swartzwelder, and Cynthia M. Kuhn.
Alcoholism: Clinical and Experimental Research, Volume 32 Issue 5 Page 754-762, May 2008.
DOI:10.1111/j.1530-0277.2008.00631.x

Click here for Abstract.

Sources: Duke University Medical Center.

Written by: Catharine Paddock, PhD