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Prenatal Exposure to Nicotine Spells Trouble Later

Study suggests lasting brain damage and susceptibility

FRIDAY, April 23, 2004 (HealthDayNews) -- Women who smoke during pregnancy expose their unborn babies to nicotine that may inflict lasting brain damage, new research claims.

These children may also be more prone to pick up the smoking habit as teens, said Theodore Slotkin, a professor of pharmacology, psychiatry, and neurobiology at Duke University Medical Center. He is the lead author of the new study, which appears in the May issue of Neuropyschopharmacology. Philip Morris USA supported the research, although the scientists have no financial ties to the tobacco company.

The studies involved animals, but Slotkin said the findings apply to humans. His team focused on animals to try to prove a biological link between smoking during pregnancy and later cognitive problems and addiction, he added.

"We already know that the offspring of women who smoke during pregnancy are more likely to become smokers in adolescence themselves," he said. "Those relationships are statistical. But there are always theories about socioeconomic factors [that lead people to become addicted to cigarettes] and other things that play in. That's why we went to the animal studies. They're all living in the same tenement. We are trying to establish a biological basis for that statistical relationship."

Slotkin's team administered nicotine or a placebo to pregnant rats. Then, their offspring got a secondary exposure to nicotine or a placebo during their "preteen" or "teen" years.

Those rats exposed to nicotine before birth had a loss of brain cells and a decline in brain activity that lasted throughout adolescence and into adulthood. "The prenatal exposure gives you permanent deficits in the way certain circuits work -- those that control memory, learning and mood," Slotkin said.

Worse yet, it seems that nicotine exposure during adolescence may be potentially more addictive because the compound seems to compensate for those cognitive losses.

Nicotine mimics the action of acetylcholine, a chemical brain messenger that plays a crucial role in learning and memory, Slotkin explained. "The way those pathways are affected, if you administer nicotine [later], you restore function," he said.

That might explain why some teens seem to get hooked on tobacco after only a few cigarettes, Slotkin said. They may have been exposed in the womb and are trying to compensate for the damage in the brain circuits that control memory, learning and mood.

The new study adds to a growing body of research about what happens to the offspring of smokers, said Dr. Joseph DiFranza, a professor of family medicine at the University of Massachusetts who researches tobacco addiction and reviewed the paper for the journal.

It's long been known, he said, that "children of women who smoke have behavioral problems" compared with those whose mothers don't smoke. Experts have wondered if the children just inherit some of the same genes or if nicotine exposure in utero might play a role.

Slotkin's study demonstrates that there may be structural damage to the brain that persists in offspring of women who smoke during pregnancy, DiFranzia said.

The research by Slotkin "may help to explain why children of smokers are particularly prone to use tobacco products," added Neil Grunberg, a professor of medical psychology, clinical psychology, and neuroscience at the Uniformed Services University in Bethesda, Md.

"Although these studies are done in a rat model, the findings are likely to generalize to humans," he said. "If so, then pregnant women should be advised that smoking during pregnancy may increase the likelihood that their children will smoke later in life and also may have long-term biological actions in these offspring."

Despite the fact that there has been a drop in maternal smoking in recent years, the researchers noted that about 25 percent of Americans have mothers who smoked during pregnancy.

More information

For more information on maternal smoking and its adverse effects, visit the National Institute on Drug Abuse. For information on teen smoking, visit the American Cancer Society.

SOURCES: Theodore Slotkin, Ph.D., professor, pharmacology, psychiatry and neurobiology, Duke University Medical Center, Durham, N.C.; Joseph DiFranza, M.D., professor, family medicine, University of Massachusetts, Worcester; Neil Grunberg, Ph.D., professor, medical psychology, clinical psychology and neuroscience, Uniformed Services University, Bethesda, Md.; May 2004 Neuropsychopharmacology
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