Sensitization and conditioning as contributors to gastrointestinal vulnerability

Electric shocks are stressful and if signalled can result in Pavlovian conditioning of the stress response. Stress arising from such shocks or conditioned psychological “threat” influences vulnerability to gastrointestinal disorders. Reviewed are our studies with rats showing that unconditioned stress experiences sensitize the glandular portion of the stomach to later restraint-in-water induced erosions, as an animal model of ulcer disease. These stress effects are not attributable to corticoids but may be opioid/endorphin dependent. The unconditioned stress-induced sensitization is reduced by allowing the rat either control over or prediction of the shocks even though the direct experience with shocks is identical. Elicitation of the conditioned stress response by a signal during the ulcer induction or even shortly afterwards increases gastric vulnerability to erosions. We are now finding parallel unconditioned stress effects on colonic erosions and increases in intestinal permeability induced by dextran sulphate sodium, as an animal model of inflammatory bowel disease. We conclude that psychological context of past trauma and/or current threat increases vulnerability to gastrointestinal disorders.