Plenty of studies have shown that mothers who smoke while pregnant could harm their baby’s brain development. But a new study from UC San Diego has found smoking while breastfeeding could be damaging newborns, too.

Researchers at UC San Diego Medical School gave newborn mice high levels of nicotine through their mothers' milk — the equivalent of one to two packs a day. Those babies ended up wanting more of the drug, said Davide Dulcis, a psychiatry professor at UC San Diego Medical School and the lead researcher.

"They were placed in cages with two bottles, one bottle with just water, and the other with nicotine saline solution," he said. "So it’s a voluntary intake, whether they drink from the water bottle or the saline solution. And what we found was the mice that were exposed to nicotine early on, they would quickly develop a preference for nicotine saline solution compared to their siblings that weren’t exposed before."

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These mice were more likely to have addictive tendencies, Dulcis said. He said the finding could also apply to human newborns of mothers who are heavy smokers or nicotine users.

That’s because when he looked at the brains of mice exposed to nicotine, there were more dopamine cells. These are known for producing feelings of pleasure or happiness. He said those cells' higher electrical activity indicated the cells would respond to nicotine when the mice reached adulthood.

So, the brains were creating a type of reward response for nicotine use. And it made the mice more likely to develop a desire for the drug as they grew up.

"In mice, we can actually look at new places in the brain and pinpoint exactly where we should look in humans to find out the mechanisms that might be involved in addiction," said Dulcis.

He added that he thinks this research could help scientists create drugs that could block addictive behaviors in humans, especially in children.

And, he said the research shows it's not just smoking while breastfeeding that could have damaging impacts on the baby, but also nicotine patches and vaping.

By Reporter Shalina Chatlani A new study from UC San Diego Medical School found addictive tendencies in mice that were exposed to nicotine in their early days. You can hear this story and other local news every morning by subscribing to San Diego News Matters, KPBS’ daily news podcast. Subscribe via iTunes, Google Play or your favorite podcatcher.

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Shalina Chatlani

Science and Technology Reporter

I cover all things science and technology — from the biotech industry in San Diego to rooftop solar energy on new homes. I'm interested in covering the human side of science and technology, like barriers to entry for people of color or gender equity issues on biotech boards.

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