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Abstract
Stress in humans commonly results in gastrointestinal dysfunction, which is characterized
by its symptomatology because the etiology is completely unknown. We developed an
animal model in which to study the effects of stress on the gastrointestinal tract,
and characterized the model as a stressor by evaluating endocrine and analgesic responses
to mild restraint. Mild restraint (wrap restraint) elevated plasma levels of adrenocorticotropic
hormone and beta-endorphin, and caused analgesia. The different regions of the gastrointestinal
tract responded differently to the stress stimulus. Gastric emptying was not affected,
small intestinal transit was inhibited, and large intestinal transit was stimulated
by stress, and there was an associated increase in fecal excretion. Wrap-restraint
stress did not result in the formation of ulcers. There was a strong correlation between
stress-induced adrenocorticotropic hormone release and stress-induced intestinal dysfunction
over a 24-h period that suggested a circadian influence. However, neither exogenous
adrenocorticotropic hormone nor beta-endorphin had any effect on intestinal transit.
Furthermore, neither adrenalectomy nor hypophysectomy prevented the response of the
intestine to stress, suggesting that neither adrenal nor pituitary-derived factors
are responsible for mediating the effects of stress on the gut. We conclude that wrap-restraint
stress produces different effects on different regions of the intestine, suggesting
that the small and large intestines are independently regulated and can respond differently
to different stimuli. There were similarities between the intestinal effects of wrap-restraint
stress in rats and intestinal symptoms associated with stress and irritable bowel
syndrome in humans. Therefore, wrap restraint may be an appropriate animal model in
which to study stress-related intestinal dysfunction. The mechanisms by which stress
affects intestinal transit are still unresolved; however, the intestinal effects of
stress are not mediated by either pituitary or adrenally derived factors.