Irritable bowel syndrome (IBS) is most often associated with gastrointestinal symptoms in the small and large intestines. IBS has been classified into four subtypes depending on stool inconsistency i.e. 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 for which is the lack of useful experimental animal models.
According to what was published by “Neuroscience News”, citing the journal “Frontiers in Neuroscience”, studies, over the years, have suggested a link between emotional states and dysfunction in the gut, emphasizing the existence and importance of the so-called “gut axis” in determining emotional well-being and representation food.
The stress of social defeat
Recently, chronic social defeat stress (cSDS) and chronic temporary social defeat stress (cVSDS) are accepted as models for major depressive disorder (MDD) and post-traumatic stress disorder (PTSD).
To answer the question, “Can animal models of chronic temporary social defeat help us understand IBS in detail?” researchers from the Tokyo University of Sciences TUS, led by Professor Akiyoshi Saitoh of the School of Pharmaceutical Sciences, used mouse models to understand the effects of prolonged stress on disease. intestinal.
The researchers found that mice under stress showed higher intestinal transit and visceral pain-related behaviors, which are hallmarks of IBS.
physical or emotional pressure
Prof. Saitoh says that during the study, the focus was “on the model of chronic temporary social defeat, and the effect of emotional stress on intestinal diseases was evaluated, in addition to evaluating the model’s potential as a new animal model for Irritable 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.
Social interaction test
On the eleventh day, 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 testing the passage of a meal of charcoal through the intestine. The researchers also evaluated the mice for intestinal permeability, defecation frequency, and fecal content.
It was found that the transit rate of charcoal, which indicates passage through the intestines, was significantly higher in rats that were subjected to emotional stress compared to rats in the control group, which were not exposed to stress. But the effects were negligible in mice that were subjected to physical stress. The frequency of defecation and the water content of the stool were also increased in rats subjected to emotional stress.
Symptoms similar to Irritable Bowel Syndrome
These effects persisted for 1 month after exposure to stress, in addition to that there were no significant differences in pathological status and intestinal permeability between mice of the control group or the emotionally stressed group, indicating the absence of changes at the tissue level due to stress.
“The findings suggest that chronic stress in mice elicits 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 discovered that changes in gut motility in experimental animals improved when cVSDS model mice were treated with a clinically used drug for 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
Speaking 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 process of dealing with stress.
In addition, the study demonstrates, for the first time, that psychological stress induced by cVSDS alone can cause IBS-D-like symptoms in mice, so further research on the cSDS and cVSDS chronic social defeat models can elucidate in more detail. regarding pathophysiological conditions and thus the design of therapies for irritable bowel syndrome.