Mouse study backs up human observations showing long-term changes.
Banishing bacteria from the body with antibiotics around birth may cause haywire signals in the brain and lasting behavioral changes, a series of studies suggests.
In the latest study, involving only mice, researchers found that low doses of penicillin given to pups before and after birth spurred changes in their blood-brain barrier and brain chemistry. The mice grew up to be more aggressive and have impaired social behavior, researchers reported Monday in Nature Communications.
That study backs up earlier work in mice, as well as in humans, showing that the microbes residing in our guts can, indeed, spark changes in our brains. In one small, notable study from 2014, researchers found that eating two servings of bacteria-loaded yogurt a day for four weeks altered brain chemistry in a dozen healthy women. This January, New Zealand researchers published a study involving 871 kids that found a correlation between getting antibiotics in the first year of life and having more behavioral problems and symptoms of depression when the kids reached the ages of seven and 11.
While the evidence for the so-called “gut-brain axis” mounts, it’s still unclear how exactly antibiotics and gut microbes interfere with our noggins. Antibiotics certainly don’t directly cause these changes. And gut microbes aren’t moving on up to better, brainier digs. Instead, researchers hypothesize that antibiotics and other disturbances in the microbial force could alter the brain and our behavior via chemical signals that sway the immune system, metabolism, and the brain itself. Gut microbes have been caught making most of the neurotransmitters our brains use to regulate themselves, including GABA, serotonin, dopamine, and norepinephrine. Gut microbes also make short-chain fatty acids, such as butyrate, propionate, and acetate, which can be involved in energy balance and metabolism. And, the intestinal-dwellers can influence cytokines, chemical signals used by the immune system.
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