Effect of intragastric administration on the morphology of laboratory rats’ gastrointestinal tract

BACKGROUND: In preclinical studies on laboratory animals, oral administration with special probe for test substances is very in demand. Most studies are devoted to the psychophysiological and clinical-biochemical reaction of the animals body to this effect, but extremely few studies consider the effect of the manipulation itself on the development of pathology in the tissues of the gastrointestinal tract associated with the inevitable mechanical impact of the probe on the mucous membranes. AIM: To identify pathological changes in the organs of the gastrointestinal tract of laboratory rats that are associated with the effects of intragastric administration of the tested substances, and compare the data obtained with the frequency of spontaneous diseases. MATERIALS AND METHODS: The data of pathomorphological observations obtained from Wistar rats involved in the course of scientific work carried out at NPO Dom Pharmacy in the period from 2018 to 2021 were used. 1400 sentinel animals were analyzed, and the same number of intact rats. Intact animals were gavaged with a control substance (distilled water) for 14 days. RESULTS: In less than 5% of clinically healthy animals, inflammatory diseases of insignificant intensity and prevalence in all parts of the intestine can be detected. As a result of the anipulation of intragastric administration, an almost twofold increase in the number of cases of catarrhal esophagitis and gastritis, erosive and ulcerative lesions of the mucous membrane of the esophagus and stomach in its glandular part and hyperkeratosis in its non-glandular part was noted. CONCLUSIONS: The type and frequency of occurrence of the background pathology of the gastrointestinal tract of laboratory rats were determined. It has been proven that repeated traumatization of the mucous membrane associated with mechanical contact of a solid metal probe with the epithelium provokes the development of inflammatory diseases of the esophagus and stomach, without affecting the underlying parts of the intestine.