Study of cold + restraint stress gastric lesions in spontaneously hypertensive, Wistar and Sprague-Dawley rats

Digestive System 1

This chapter deals with the digestive system. The major and minor salivary glands and their secretions also represent and integral part of the protective mechanism of the oral cavity, and derangement of saliva production may lead to loss of integrity of the oral mucosa. Drug-induced abnormalities of taste sensation are also well-described phenomena occurring in man although human studies are necessary for the detection of these effects. Inflammation of the oral cavity may involve the buccal mucosa, the gingiva (gingivitis), the tongue (glossitis), and the peridontal tissues (peridontitis). Therapeutic agents can induce inflammatory lesions in the tongue. Moreover, a protective layer of mucus, a visco-elastic material containing high molecular weight glycoproteins produced by the major and minor salivary glands, covers the stratified squamous mucosa of the oral cavity. Salivary secretions also possess digestive enzyme activity although in herbivores and carnivores, it is usually low in contrast to high digestive enzyme activity in omnivorous species.

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.

Experimental stress ulcer and gastric catecholamine contents in spontaneously hypertensive rats

To determine the role of the sympathetic nervous system in the development of stress ulcer, we carried out experiments on spontaneously hypertensive rats (SHR) exposed to restraint and water immersion stress for 7 h. Normotensive Wistar-Kyoto rats (WKY) were used as controls. Catecholamine (CA) contents in gastric tissues, divided into mucosal and muscular layers of both antrum and corpus, were quantitated by high-performance liquid chromatographic electrochemical detection (HPLC-EC). The stress ulcer formation was much less frequently induced in SHR than in WKY. The noradrenaline (NA) contents in all regions of gastric tissues were higher in SHR than in WKY. The contents of adrenaline (A) and dopamine (DA), present in small quantities in gastric tissues showed no difference between SHR and WKY. After exposure to stress, the NA contents in mucosal and muscular layers of the gastric corpus decreased significantly in both SHR and WKY, whereas the value remained higher in the former. On the contrary, a remarkable increase of A contents (probably released from the adrenal medulla by the stress) was observed in all gastric tissues, of both SHR and WKY. Increase of the A contents in the mucosal layer was remarkable in the SHR. The DA contents increased in both strains. These results suggest that the peripheral sympathetic hyperfunction in the stomach in the SHR may have an inhibitory role in stress ulcer formation.

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.

Stress ulcer in normotensive and spontaneously hypertensive rats

Spontaneously hypertensive rats (SHR) and their normotensive progenitors, the Wistar-Kyoto (WKY) rats, were tested in the open-field arena and subsequently exposed to either cold-restraint stress or activity-stress. SHR rats were more active and judged less fearful in the open-field test. Changes in core body temperature, and adrenal and thymus weights did not differentiate between SHR and WKY rats in the cold-restraint procedure. A significant adrenal hypertrophy was observed for SHR rats in the activity-stress procedure. WKY rats were more susceptible to stress ulcer in both the cold-restraint and the activity-stress procedures. While running-wheel activity had been considered an important etiological variable for activity-stress ulcer, the lower activity demonstrated by the ulcer-prone WKY rats suggested that genetic variables might be more relevant to stress ulcer disease.

Altered patterns of mucin secretion in gastric hyperplasia in mice

Gastric hyperplasia occurred more frequently among densely housed mice than mice housed singly, and crowding stress may have been implicated in this increased prevalence. Affected stomachs had striking increases in sulfomucin secretion when compared with unaffected gastric mucosa. The mucin changes suggested incomplete maturation of mucous cells in this condition and were similar to those reported in association with early neoplastic or pre-neoplastic lesions in the stomach of both man and rodents.

Stress of immobilization: description and validation of a restraining technique for rats

Various techniques have been developed over the past several years to study the effects of the stress of immobilization on the rat. The technique proposed in this paper provides effective restraint. It has the added advantage that potentially contaminating effects of uncontrolled secondary stressors are limited. The technique was tested in five groups of rats which were subjected to 0, 1, 2, 3, or 4 periods of immobilization, respectively, each lasting 12 hr. with 12-hr. intermittent rest periods. Results attested to the effectiveness of the technique in that, when compared to appropriate controls, an hypertrophy of the adrenals and the testicles was observed, accompanied by concomitant losses of whole body weight, in the experimental animals. The treatment had no effect on the thymus, and no gastric ulcers were produced. The relative mildness of the effects is interpreted less as a sign of the inadequacy of the technique than as an indication that not all parameters were examined during the periods of immobilization.

Physiological and biochemical concomitants of restraint stress in rats

Restraint stress of 30 min increases plasma CS and lowers hypothalamic NE. Restraints of longer durations are associated with an attenuation of these changes. Daily repetitive restraint enhances the CS response on the second day and progressively diminishes it on subsequent days. Whole brain NE increases on the first day and decreases on Day 2 to 5. The CS response to acute restraint is similar in 5 different normotensive rat strains, but is enhanced in the genetically hypertensive SH rat, its normotensive backbreed WKY, and the DOCA hypertensive Sprague-Dawley rat. Comparison with other stressors (electric foot shock and novel environment) indicate that the responses to restraint are different at least in time course, if not qualitatively.