Irritable bowel syndrome (IBS) is most often associated with gastrointestinal symptoms in the small and large intestines. IBS has been classified into four subtypes according to stool inconsistency, such as IBS with constipation IBS-C, with diarrhea IBS-D, mixed IBS-M, or unclassified IBS.
However, there is a lack of understanding in the scientific literature regarding the mechanisms and treatments of IBS, one reason being the lack of useful experimental animal models.
According to what was published by “Neuroscience News”, quoting the journal “Frontiers in Neuroscience”, studies, over the years, have suggested a link between emotional states and dysfunctions at the intestinal level, underlining the existence and importance of so-called “intestinal axis” in determining emotional well-being and the representation of food.
The stress of social defeat
Recently, chronic social failure stress (cSDS) and chronic temporary social failure stress (cVSDS) are accepted as models for major depressive disorder (MDD) and posttraumatic stress disorder (PTSD).
To answer the question: ‘Can animal models of chronic temporary social defeat help us understand IBS in detail?’, the TUS researchers, led by Professor Akiyoshi Saitoh of the School of Pharmaceutical Sciences, used mouse models to understand the effects of prolonged stress on intestinal disease.
The researchers found that mice under stress displayed higher intestinal transit and visceral pain-related behaviors, which are the hallmarks of IBS.
physical or emotional pressure
The professor. Saitoh says that during the study, the focus was “on the temporary chronic social defeat model, and the effect of emotional stress on intestinal disease was evaluated, as well as assessing the model’s potential as a new animal model for cases of Irritability Bowel Syndrome”.
In their study, the researchers subjected mice to physical or emotional stress: the experimental animals were subjected to physical or psychological aggression for 10 minutes a day for 10 consecutive days.
Proof of social interaction
On day 11, a social interaction test was performed to assess the stress conditions of the experimental animals. Fatigue was also estimated by quantifying the amount of corticosterone in plasma and by testing the passage of a charcoal meal through the gut. The researchers also evaluated the mice for intestinal permeability, defecation frequency, and fecal content.
It found that the transit rate of coal, which indicates its passage through the intestines, was significantly higher in rats subjected to emotional stress than in control rats, which were not exposed to stress. But the effects were negligible in mice subjected to physical stress. Defecation frequency and stool water content also increased in rats subjected to emotional stress.
Symptoms similar to irritable bowel syndrome
These effects persisted for 1 month after stress exposure, and there were no significant differences in pathological status and intestinal permeability between mice in the control group or in the emotionally stressed group, indicating no tissue-level changes due to stress. stress .
“The results suggest that chronic stress in mice causes IBS-D-like symptoms, such as chronic intestinal aggravation and abdominal hyperalgesia, without the presence of intestinal lesions,” says Professor Saitoh.
Surprising note
Interestingly, the researchers found that the changes in intestinal motility in the test animals improved when the cVSDS model mice were treated with a drug used clinically for irritable bowel syndrome (IBS).
The study highlights the advantage of the cVSDS chronic temporary social defeat model over traditional methods of inducing IBS-D-like symptoms through exposure to repetitive psychological stress.
The role of the cerebral cortex
Talking about the mechanisms of these effects, Prof. Saitoh says: ‘From the gut-brain axis, it is suggested that the cerebral cortex plays an important role in determining the phenotype of emotionally stressed mice.’ The insular cortex is part of the upper central nervous system that controls digestive functions and is involved in the stress management process.
Furthermore, the study demonstrates, for the first time, that psychological stress induced by cVSDS alone can cause IBS-D-like symptoms in mice, thus further research on cSDS and cVSDS models of chronic social defeat can clarify in more detail. conditions and thus the design of therapies for irritable bowel syndrome.
