The researchers base their findings on analysis of gut tissue taken from rats subjected to either water avoidance stress, which involves placing the rat on a small platform surrounded by water, or sham stress for one hour a day for 10 consecutive days.
The stress sessions were designed to mimic psychological stress to produce the type of effects that would be seen in the human gut.
Half the rats were fed drinking water containing probiotic bacteria in the form of Lactobacillus helveticus and Lactobacillus rhamnosus for a period of seven days before and during the stress sessions.
Unlike sham stress, brief but repeated water deprivation made the gut "leaky" and boosted the adherence of harmful bacteria to the cells lining the gut wall.
Bacteria were also detected in the mesenteric lymph nodes, which drain fluid coming from the intestine, indicating that bacteria had entered the body and activated the immune system.
However, probiotic treatment minimised the changes in chemical signalling and prevented bacterial "stickiness" and movement to the mesenteric lymph nodes.
Chronic stress is known to be implicated in the development of irritable bowel syndrome and in the worsening of symptoms of inflammatory bowel disease, such as Crohn's disease and ulcerative colitis. It also sensitises the gut, producing allergies to certain foodstuffs.
The authors say that probiotics literally compete for space with harmful bacteria and dampen down inflammatory responses, and as such, offer a potentially promising approach to the management of intestinal problems caused by stress.
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