Complex Neurobehavioral Testing of a Rat Model of the Irritable Bowel Syndrome

In albino Wistar rats, the irritable bowel syndrome (IBS) was induced by chronic restraint stress (restriction of the animals in plastic containers, 6 h per day during 7 days). In the Y-like maze, IBS rats demonstrated smaller numbers of spontaneous alternations (indices of immediate spatial memory; P < 0.05) than control animals. In the elevated plus maze, IBS rats showed a significantly reduced time spent in the open arms (P < 0.03) compared to the controls, suggesting anxiety-like effects. Moreover, episodes of stretching in this maze were more numerous in the IBS group (P < 0.05), also suggesting anxiogenic effects. Some depression-like behavior of IBS rats was observed in the forced swimming test, as was demonstrated by a significantly shorter mobility time, as compared to the control group (P < 0.05). In the radial 8-arm maze, however, chronic stress-induced IBS did not significantly affect the number of reference memory errors and time necessary for completing the task. Still, some working memory deficit was observed in the IBS group in this test, as the number of the respective errors was significantly greater (P < 0.05) in such rats vs. controls within some time intervals. In the open field test, suppression of locomotor activity (reduced number of square crossings), significantly increased number of rearings (suggesting higher anxiety), and altered fecal elimination in the IBS group were obvious (P < 0.05). Also, an increased time of grooming was observed in IBS rats in the above test (characterizing a higher anxiety level in the stress-exposed IBS group). When zoosocial behavior was tested in a three-chambered apparatus (10-min-long period of testing), rats of the IBS group spent significantly more time in the empty compartment (without a stranger rat) and less time in the compartment with a conspecific of the same age and weight (P < 0.01), which indicates decreased social motivation in the IBS group. Our results suggest that the aforementioned chronic stress-induced IBS model results in increased anxiety, depression, and suppressed social behavior. The IBS affects immediate and working memory (with nearly no effect, however, on reference memory).

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