Alcohol's Drug Properties Reinforce Its Effects

Smell and Taste Not As Important, Study Shows

Newborn Baby
Early Alcohol Exposure Is Damaging. © Getty Images

Children who have been exposed to the reinforcing effects of alcohol in the womb or in early infancy through breastfeeding are much more likely to develop alcohol problems later in life.

Some studies using laboratory animals have found that infants (but not adults) might find the taste of alcohol reinforcing. Infant rats will consume drinks containing up to 30% alcohol, while adults will rarely consume anything higher than 6% alcohol.

Other studies have found that the pleasant effects produced by alcohol reinforces drinking behavior. Alcohol positively reinfoces drinking by producing mild euphoria.

Which of these reinforcing effects influence children to turn to alcohol later in life? Is it the taste? The smell? Or is it how it makes them feel?

Researchers at Binghamton University believe that the reinforcing properties of alcohol during infancy are due to its pharmacological effects.

The 'Reinfocing' Effects of Alcohol

"In terms of brain development, the first 10 days or so after birth for the rat is, very roughly, equivalent to the third trimester of the human fetus," said Elena I. Varlinskaya, associate research professor at Binghamton University and corresponding author for the study. "The extent to which alcohol is considered "reinforcing" is measured by the extent to which the animal approaches rather than avoids the predictor of alcohol's effects, in this case, a surrogate nipple.

Previous research has indicated that infants, but not adults, might find the taste of alcohol reinforcing.

"Infants readily consume even high concentrations, up to at least 30 percent alcohol, whereas adults are reluctant to consume concentrations higher than six percent alcohol, and will do so only after weeks or months of training; even then they will rarely accept an alcohol concentration higher than 10 percent.

Pharmacological Effects of Alcohol

"Alcohol reinforcement in adult rats has been attributed largely to its pharmacological consequences. This was much less clear for infant rats, which is the reason for the present study."

"Fetuses and infants have an amazing capacity to learn and form associations among events in their environment," added Jennifer D. Thomas, assistant professor of psychology at San Diego State University. "If an infant is exposed to the odor of alcohol in the environment, or the combined taste, odor and pharmacological effects of alcohol during fetal development or breastfeeding, it is important to determine how this experience affects preference for alcohol and levels of alcohol consumption later in life.

Reinforcing Properties of Ethanol

"In fact, studies indicate that fetal exposure to alcohol is associated with subsequent alcohol use and abuse. This study demonstrates that the pharmacological effects of alcohol, independent of orosensory cues, contribute to the reinforcing properties of ethanol in the developing fetus/infant."

To determine which properties of alcohol motivated infant rats, the researchers set up three experiments with 196 newborn lab rats.

The first experiment paired sucking on a nipple with providing water with alcohol administered through an abdominal injection. This minimized the smell and taste attributes of alcohol.

In the second experiment, an empty nipple was paired with alcohol and water delivered apart from the nipple. Experiment three measured blood alcohol content five minutes and 60 minutes after one of four doses of alcohol administered through an abdominal injection.

The Rewarding Effect

"Our key finding is that an injection of alcohol, with essentially no accompanying taste or odor, is sufficiently reinforcing to allow a newborn rat to learn with only a single experience what predicted the alcohol," said Varlinskaya. "Since there was negligible odor, taste or calories involved, the rewarding effect of injected alcohol must be derived from its effect on areas of the brain activated by drugs of abuse rather than the taste or smell.

Damaging the Brain

"This implies that the basis of alcohol reinforcement is the same in newborn rats as in adults. This suggests that animals and people may find alcohol rewarding for the same reasons throughout their development."

"From a basic science standpoint," added Thomas, "this study will help us to understand the development of brain regions important for the reinforcing effects of alcohol and the types of associations that can be learned.

"The study has implications for infants exposed to alcohol in utero or via breastfeeding. Exposure to alcohol during development can be teratogenic, damaging the brain and altering behavioral development.

Sources:

Lewis, MJ. "Alcohol reinforcement and neuropharmacological therapeutics." Alcohol and Alcoholism March 1996

Petrov, ES, et al. "Reinforcement From Pharmacological Effects of Ethanol in Newborn Rats." Alcoholism: Clinical & Experimental Research October 2003

Wilkie, H et al. "Reinforcing mood effects of alcohol in coping and enhancement motivated drinkers." Alcoholism: Clinical & Experimental Research May 2005

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