Internal Bacteria May Alter Brain Chemistry 
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 Internal Bacteria May Alter Brain Chemistry

Internal Bacteria May Alter Brain Chemistry

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Rachael Rettner
May 22, 2011

The role of gut bacteria in the body may extend beyond the stomach and
intestines all the way to the brain, a new study in mice suggests.

The results show disrupting the normal gut flora of the mice leads to
changes in the animals behavior, making them less timid and more
adventurous, as well as leading to changes in their brain chemistry.

Although its not clear if the same thing happens in humans, the
findings may explain why some gastrointestinal diseases, such as
irritable bowel syndrome, are often associated with disorders that can
affect behavior, including depression and anxiety.

It may be that those changes in gut bacteria not only contribute to
the generation of gut symptoms, like diarrhea or pain, but may also
contribute to this altered behavior that we see in those patients,
said researcher Stephen Collins, of the Farncombe Family Digestive
Health Research Institute at McMaster University in Ontario, Canada.

The study is published online in the journal Gastroenterology.

Bacteria and behavior

Previous studies have suggested gut bacteria may communicate with the
brain. For instance, some people with liver disease experience changes
in mental abilities that improve after they are given antibiotics.
Other studies have shown mice that dont have gut bacteria respond
differently to stress compared with those that do.

To further investigate the link, Collins and his colleagues first gave
healthy mice antibiotics to disturb their natural gut bacteria. The
mice became less anxious they were less hesitant to step off a
platform and more eager to explore. When their gut bacteria was
restored to normal, so was their behavior. Control mice that were
given water instead of antibiotics showed no changes in behavior. Mice
that didnt have any gut bacteria also showed no changes in behavior
when they received antibiotics.

Disrupting the contents of the gut also appears to affect brain
chemistry. Mice given antibiotics had an increased amount of a brain
protein called derived neurotrophic factor, or BDNF, in their brains
compared to control mice. Changes in the levels of BDNF have been
previously linked to depression and anxiety.

Next, the researchers carried out some gut bacteria swapping of sorts.
Different strains of mice are known to exhibit different behavior
patterns. Some are more anxious while others are aggressive and
hyperactive. The researchers took mice from both extremes and
exchanged their gut bacteria. They saw the behavior flipped as well
the anxious mice became more active and daring and the aggressive mice
became more passive.

Probiotics for the brain

The researchers suspect the bacteria are producing chemicals that can
access and influence the brain, Collins said.

If gut bacteria play some role in human behavior as well, its
possible therapies that aim to restore normal gut flora, such as
probiotics, may be helpful in correcting behavior and mood changes in
those with gastrointestinal diseases, Collins said.

Collins and his colleagues are now studying the gut bacteria
composition of patients with gastrointestinal disorders. They want to
see whether the content differs among those who have symptoms of
depression and anxiety compared with those who do not.

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Wed, 08 Jan 2014 09:25:36 GMT
 [ 1 post ] 

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