Environmental and genetic effects on food-deprivation induced stomach lesions in male rats

The effects of food deprivation, nutritive and non-nutritive feeding and wheel running on gastric stress ulcers in rats

Feeding and housing conditions that induce gastric lesions were investigated. Rats were housed in activity wheels or in hanging cages and exposed to food deprivation, ad lib cellulose or 6 g of cellulose per day for 5 days. Food-deprived rats in both housing conditions had ulcers in the rumen but many rats also had mucosal ulcers. Cellulose prevented rumenal ulcers but produced a tendency toward more severe mucosal ulcers. Ulcers in wheel-housed rats were somewhat larger but the difference was not significant. In a second experiment, rats were fed 6 g/day laboratory chow or 6 g/day chow + ad lib cellulose until b.wt. reached a preset criterion. On the average, about 10 days on the feeding regimen were required to induce ulcers in these groups. None of the rats had rumenal ulcers. Mucosal ulcers were reliably larger in rats that received cellulose in addition to 6 g of chow. There was no difference in ulcer area between wheel-housed and cage-housed rats. The results indicate that solid bulk, regardless of its caloric value or amount, protects the nonglandular stomach whereas noncaloric bulk tends to aggravate ulcers in the glandular stomach. A small amount of chow delays the rate of b.wt. loss and consequently ulcer formation. Furthermore, wheel running is not necessary to produce mucosal ulcers when food intake is insufficient to maintain b.wt. and b.wt. at sacrifice seems to be a good predictor of ulcer formation.

Depressive behavior and stress ulcer in Wistar Kyoto rats

Wistar Kyoto (WKY) rats, as compared to several other rat strains, are hypoactive in the open field test and in the defensive burying test. WKY rats readily acquire a learned helplessness task as well as a passive avoidance tasks. WKY rats also reveal a greater susceptibility to restraint-induced stress ulcer. The behavioral tests suggest the presence of depressive behavior in WKY rats. When exposed to the Porsolt forced-swim test of 'behavioral despair', WKY rats are judged as exhibiting more depressive behavior. Desipramine not only reduced immobility in the forced-swim test, but also diminished the severity of restraint-induced stress ulcer. These data suggested a heightened activity of the hypothalamic-pituitary axis. Basal plasma ACTH levels did not differ between WKY rats and Wistar rats, but serial plasma ACTH response to restraint stress was significantly greater for WKY rats. These data suggest that depressive behavior is a characteristic of WKY rats and this strain is a valuable model for studying depression which may be induced by an exaggerated stress response.

The neurobiology of stress ulcers

We have reviewed the neurobiology of stress ulcers from animal models to potential pharmacotherapeutic mechanisms. The evidence strongly supports the hypothesis that certain stress-related gastric lesions are 'brain-driven' events which may be more effectively managed through central manipulations than by altering local, gastric factors. Recent advances in the use of anxiolytic and antidepressant drugs in the management of stress-related gastric mucosal injury further supports the contention that a brain-gut axis, which may have nervous, peptidergic and classic monoaminergic components, modulates the intricate and complicated pattern of communication between the brain and the stomach. Delineation of the precise pathways which make up this communication as well as their manipulation by various pharmacological agents will be the focus of future research endeavour.

Genetic and histological aspects of stomach lesions induced by systemic injection of phenylbutazone in the rat

Roman high-avoidance (RHA/Verh) rats, food-deprived (F-D) for 5 days, had higher stomach lesion scores than did F-D Roman low-avoidance (RLA/Verh) rats. F-D RLA/Verh rats which were injected i.p. with phenylbutazone (PBZ) 24 h before examination, however, had higher scores than did PBZ-treated, F-D RHA/Verh rats. Histologically, extensive edema and cellular infiltration (including numerous erythrocytes) were seen below the lesions, in the submucosa, denoting vascular damage. An attenuating influence of food on the ulcerogenic effects of PBZ, which were much more severe in F-D than in fed rats, was also indicated.