Stress effects on gastrointestinal transit in the rat

Previous investigations of stress effects on gastric emptying, orocaecal, and colonic transit in rats have produced conflicting results. Here one type of stressor, a 'passive avoidance' situation, was used to investigate its effects on gastric emptying, orocaecal and colonic transit. After the rats had been trained to eat a standard amount of semisolid food, gastric emptying was determined (n = 12) by the food remaining in the stomach after various periods of rest, or stress exposure. Orocaecal transit (n = 14) was determined by breath hydrogen measurements after the food had been labelled with 1 g lactose. Colonic transit (n = 18) was measured as the arrival time of coloured faeces after infusion of a carmine red solution into the caecum through a chronically implanted catheter. The stressor had differential effects on transit through the stomach, small bowel and colon: gastric emptying was delayed (p less than 0.05) after stress (t1/2 = 2.66 h after stress, 1.97 h at rest). Orocaecal transit was accelerated (p less than 0.05) after stress; transit time decreased from 124.3 min at rest to 86.2 min after stress. Colonic transit was accelerated (p less than 0.01) under stress, from 15.5 h to 1.29 h. It is concluded that gastrointestinal transit in different parts of the gastrointestinal tract is differently affected by central nervous stimuli.