In a study of adult monkeys who were exposed to moderate amounts of alcohol in utero, scientists have found that prenatal exposure to alcohol - even in small doses - has pronounced effects on the development and function later in life of the brain's dopamine system, a critical component of the central nervous system that regulates many regions of the brain.
Writing in the current issue of the journal Alcoholism: Clinical and Experimental Research, a team of researchers led by Mary L. Schneider, a University of Wisconsin-Madison professor of occupational therapy and psychology, reports that when a monkey exposes her fetus to alcohol by drinking, the dopamine system of her offspring is altered. Effects on that key neural system, according to the study's results, can manifest themselves up to five years after birth, when the monkeys are fully grown.
The influence of alcohol on the dopamine system, depending on the timing of exposure during gestation, varies, says Schneider, but illustrates yet another biological consequence of drinking while pregnant.
"It appears that there is no safe time to drink," says the Wisconsin researcher. "And because our study looked at the effects of lower doses of alcohol than most previous studies, the results suggest there is no safe amount of alcohol that can be consumed during pregnancy. Even moderate drinking can have effects that persist to adulthood."
The new study, conducted at UW-Madison's Harlow Center for Biological Psychology, looked at the effects of moderate drinking on the offspring of three groups of pregnant rhesus macaques, each of which were provided access to moderate amounts of alcohol during various stages of gestation. In addition, there was a control group not exposed to alcohol.
Working with UW-Madison professor of medical physics Onofre DeJesus, Schneider's group used PET scans to assess the function of the dopamine system of the adult monkeys exposed to alcohol in utero.
Dopamine is a key chemical messenger in the brain, helping it perform an array of functions ranging from simple movement to cognition to facilitating feelings of enjoyment and motivation. Perhaps the best-known dopamine-related pathology is Parkinson's disease, caused by the death of the brain cells that normally secrete the chemical. But abnormalities in the functioning of the system can also contribute to such things as addiction, issues of memory, attention and problem solving, and more pronounced conditions such as schizophrenia.
In the new study, Schneider's group used positron emission tomography or PET on the now-grown monkeys to evaluate the interplay of dopamine receptors and enzymes at work in the system. Schneider and her colleagues were able to see the chemical interplay in the brains of the monkeys exposed to alcohol in utero, and detected a range of effects, especially in the striatum, a region of the brain associated with cognition and other key functions.
"We're seeing receptors and enzymes that are important in producing dopamine, and what was surprising to us was that dopamine was altered in opposite directions" depending on when during gestation the monkey's developing brain was exposed to alcohol.