The experimental production of resistance to stress-induced stomach lesions in the rat

Stress ulceration in rats: impact of prior stress experience

The role of prior stress experience on the response of the organism to a later stressor has been studied in terms of the extent of gastric ulceration induced by the second stressor. These studies have focused largely on effects of prior stress (shock, restraint, activity) on the ulceration developing under later restraint and activity stress. The studies indicate that prior exposure to restraint stress provides some protection against later restraint ulcer development. Using shock as the prior stressor, the effects on later restraint stress are determined by the particular characteristics of the shock (controllability and predictability), and by contextual factors. Studies are lacking on the significance of these characteristics of shock for later activity stress ulcers. Further studies are required therefore on the significance of psychological characteristics of the prestress, and on the effects of these prestressors at different stages of the life cycle. The identification of these factors, and a clearer picture of the protective and exacerbating effect of prior stress will allow us to explore the physiological (central and peripheral) mechanisms underlying ulcer development and ulcer susceptibility.

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.

Restraint stress in biomedical research: a review

The use of restraint or immobilization for investigations of animal physiology, pathology and pharmacology has an extensive history. The major use of this technique has been as a "stressor" for the induction of stress response syndromes in animals. Many such syndromes have been characterized from the behavioral level to the neurochemical concomitants of stress. As a consequence of this particular use of the restraint procedure, much information concerning drug effects on stress response syndromes has been obtained. Indeed, many researchers in the area of gastrointestinal drugs routinely screen their new compounds in a restraint model of gastric stress ulcer. The purpose of this review is to present for researchers, a summary of the methods for, the parameters of, and known drug effects on, restraint-induced pathology. In our experience, this technique has proven to be a very useful one for the examination of both central and peripheral mechanisms of stress-related disorders, as well as for studying drug effects upon these disorders.

Serial stressors: prior exposure to a stressor modulates its later effectiveness on gastric ulceration and corticosterone release

Several studies have focused on the proactive effects of prior exposure to a stressor on ulcerogenic and endocrine responses to exposure to a similar final stressor. In the present study, we explored the effects of prior exposure of Møll-Wistar rats to water-restraint stress on gastric ulceration and corticosterone responses to a final stressor. The number of prior exposures to water-restraint challenge was varied from one to four, and the durations of the prior exposures varied from 30 min to 2 h. The duration of the final stress challenge was 75 min. The two indices of the stress response to the final stressor challenge yielded different results. For neither index was the duration of prior exposures a significant factor in modulating the response to the final challenge. For gastric ulceration, those animals receiving one prior exposure, but not four, exhibited less gastric ulceration than animals receiving no prior exposure. These animals also developed less ulceration than those receiving four prior exposures. For corticosterone, those animals receiving four prior exposures exhibited a lower adrenocortical response to the final stressor than did animals receiving no prior exposure, or only one prior exposure. The results indicate the complexity of proactive effects of earlier stress experience on responses to a final stressor challenge.

Interactions amongst factors which influence severity of gastric ulceration in rats

A number of factors have previously been demonstrated to influence the severity of stress-induced gastric ulceration in rats, including prior exposure to pre-shock and allowing animals a post-stress rest or recovery period. The primary purpose of this experiment was to investigate how one of these factors might modulate the expression of the other. Animals were pre-exposed to either signalled or unsignalled shock (using "learned helplessness" parameters), or no shock. They were later subjected to 2 hours restraint-in-water (immersion) stress, or appropriate handling control procedures. Half of the animals were sacrificed immediately on removal from the water-restraint, and half were sacrificed after a 2 hour recovery period in their home cages. Analysis of the severity and number of glandular stomach lesions indicated that animals subjected to the pre-shock exhibited greater ulceration than unshocked animals, as long as no post-stress rest period was allowed. Additionally, the effect of post-stress rest was masked by experience with pre-shock. This reciprocal modulation of treatment influences may offer suggestions for understanding discrepancies in the literature on the effects of these two modulating variables.

Prior stress and susceptibility to stress ulcer

Rats were exposed to daily sessions of either restraint plus cold, forced exercise, or grid shock for one month and then subjected to the ulcerogenic effects of either supine restraint plus cold, or activity-stress. Chronic stress generally protected against stress ulcer but the protection depended on the degree of similarity between the pre-treatment stressor and the ulcerogenic procedure. Pre-treatment with restraint plus cold provided protection which applied not only to supine restraint plus cold but also generalized to activity-stress. Foot-shock pre-treatment did not significantly reduce restraint ulcer but it significantly exacerbated activity-stress ulcer.