Researchers at the State University of New York (SUNY) Upstate Medical University have uncovered new evidence to explain why teenagers whose mothers drank alcohol during pregnancy are particularly at risk for heavy drinking and alcohol addiction: These youths may be primed for abuse because their developing senses came to favor alcohol's taste and smell in the womb.
In two studies funded by the National Institutes of Health and published in December's Behavioral Neuroscience (Vol. 121, No. 6), researchers at SUNY's Developmental Exposure Alcohol Research Center observed that infant rats appear to develop a nervous system that has adapted to whatever a mother consumes during pregnancy.
"There's a tremendous amount of neural plasticity available during development," says lead researcher Steven Youngentob, PhD, a professor of neuroscience and physiology at SUNY. "One of the ways animals learn about what is good to eat is through what mom ate during pregnancy and breastfeeding."
As the developing nervous system senses ethanol in amniotic fluid, it cultivates a liking to it in the same way it would to something healthy, such as milk or carrot juice, Youngentob explains.
"A normal adaptive process that should work to the advantage of the animal is actually working to the disadvantage of the animal in the context of a drug of abuse," he adds.
In one study, rats exposed to ethanol in the womb drank significantly more of it as youths-but not in adulthood-than did control animals, whose pregnant mothers ate only chow. In a second study, researchers again exposed the rats to ethanol by giving it to pregnant animals, and they tested the offspring 15 or 90 days after birth. When exposed to ethanol odor, the prenatally exposed rats were behaviorally more responsive to the odor than control rats were.
These effects faded by adulthood-the rat equivalent of 30 to 40 human years-because the rats had no further exposure to the alcohol. That's good news for at-risk teens, Youngentob points out: Steering at-risk adolescents away from alcohol could help head off addiction as adults.
But, he adds, "The even more basic message is that there is no time during pregnancy when it is safe to drink."