Stress ulcers in rats: the role of food intake, body weight, and time of day.

Rats were housed in activity wheels (n = 32) or in hanging cages (n = 32) for 2 weeks. Food intake of rats in hanging cages was curtailed to match body weight to that of the activity group. All rats then received 6 g of food at one of four different times of day (n = 8, each mealtime) for 4 consecutive days and were sacrificed 24 h after the last meal. Twenty-three rats in the activity group and 13 rats in the hanging cage group had ulcers in the glandular portion of the stomach. Ulcers were significantly larger and more numerous in the activity group, and activity levels were highly correlated with area of ulceration. In both groups, terminal body weight was also significantly correlated with area of ulceration. No statistically reliable mealtime effects were observed because of large within-group variability. Because many rats in hanging cages developed ulcers in the absence of wheel running, the results suggest that restricted food supply and loss of body weight are initiating factors in ulcer formation, while excessive wheel running contributes to the severity of ulcerations in the glandular stomach.

Activity-stress ulcers in rats: the role of preentrainment to meal time.

Rats housed in activity wheels (A-W) or hanging cages (H-C) received food restriction to 4 h/day for 15 days. Food was given at fixed times to entrain the feeding entrainable oscillator or at irregular times to prevent entrainment. One half of the rats received food in the light phase, the other half in the dark phase of the light-dark cycle. Food was then reduced to 6 g/day for 4 days for A-W rats or 7 days for H-C rats. Stomachs were removed 24 h after the last meal and the ulcerated area was quantified. Twenty one of 32 A-W rats and 19 of 32 H-C rats had ulcers in the glandular stomach. Ulcers were significantly larger in A-W rats (p < 0.01). Activity levels (in A-W rats), % body weight loss and terminal body weight (in both groups) were significantly correlated with the area of ulcers. There was no significant time of day effect on the ulcer severity. However, an unexpected finding was that for A-W rats, those fed at fixed times had larger ulcers than those fed at irregular times (p < 0.01) while H-C rats showed an expected trend in the opposite direction. One possible explanation for this result is that for A-W rats, the reduced food supply at an expected time of day generated a greater stress response than in rats whose feeding time was unpredictable.

Diet-induced obesity attenuates anticipation of food access in rats.

Rats were housed in hanging cages and given ad lib access to food (control), approximately 20 g food/day (lean), or a palatable high-fat diet (fat). After body weights diverged, rats were transferred to activity wheels. When food access was reduced to 2 h/day, all control and lean rats displayed anticipatory activity (AA), while only two of eight fat rats anticipated the meals. Baseline activity levels and nonanticipatory wheel running were only marginally reduced in fat rats. In a second experiment, conducted entirely in activity wheels, rats were maintained on curtailed food or a high-fat diet until body weights diverged. Food access was then reduced to 2 h/day and the diets were reversed. Lean rats given restricted access to the high-fat diet gained weight and four of eight rats showed AA. Fat rats switched to chow lost weight and all eight rats displayed AA. The results indicate that body weight changes induced by diet manipulations result in a striking and rather selective reduction in the anticipation of daily meals. This effect is ascribed to a modulation of the output of a circadian pacemaker that entrains running-wheel activity to daily meals.

New methods to detect the effect of alteration in gastric pH and intestinal transit by metoclopramide and propantheline using a continuous gastric pH probe and hydrogen breath analysis.

UNLABELLED: The effects of oral doses of metoclopramide (M, 10 mg) and propantheline (P, 30 mg) on alteration in gastric pH and emptying were determined using a continuous pH probe (Digitrapper, Synectics) and hydrogen breath analysis (HBA, QuinTron) in eight male subjects. The four phases consisted of HBA, HBA and pH probe, and HBA and pH probe and either P or M. Baseline pH measurements were recorded for 60 min prior to dosing with 10 g of lactulose in three of the periods. Dosing with P or M was given 30 min before administration of lactulose. HBA and continuous gastric pH were measured for 120 min. M produced earlier and higher peak hydrogen concentration than control (p less than 0.0001). P decreased peak hydrogen and increased gastric pH from approximately 2.0 to 4.0 (p less than 0.0001). CONCLUSIONS: 1) HBA can be used to detect alterations of intestinal motility; 2) The gastric pH probe produces a small increase in intestinal motility; and 3) The combination of the gastric pH probe and HBA could be a useful technique to simultaneously evaluate gastric pH and gastrointestinal motility.