An experimental gastric ulcer of the rat produced with anticholinergic drugs under stress

[An overview of acetic acid ulcer models and their utility for drug screening]

Since Takagi et al. reported an experimental chronic gastric ulcer model [acetic acid ulcers induced by submucosal injection of acetic acid (Type 1)], we further modified the methodology and subsequently devised three more models. The second model involves inducing ulcers by serosal application of an acetic acid solution (Type 2) and the third model achieves ulcer induction by intragastric application of an acetic acid solution (Type 3). The forth model was modification of the third model by giving the acetic acid solution and the same volume of air to make one ulcer in the stomach (Type 4). In general, animals accepted the procedures without problems and no undesirable effects were noticed. More importantly, this experimental animal model allows production of ulcers that highly resemble human ulcers in terms of both pathology and healing. Indeed, relapse is even endoscopically observed for 360 days after ulceration. The ulcers produced not only respond well to various anti-ulcer medications, such as antisecretory and mucosal protective drugs and growth factors, but also demonstrate appropriate responses to ulcerogenic agents such as NSAIDs. In addition, we have recently demonstrated that H. pylori infection resulted in delayed ulcer healing and recurrence of healed acetic acid ulcers induced in Mongolian gerbils. The present article gives a brief summary of the ulcer history before establishment of acetic acid ulcers and characteristic features of acetic acid ulcer, including both their merits and shortcomings.

Autonomic drug effects and gastric secretion in a new experimental model of stress ulcers in rats

A psychological procedure which does not involve the application of physical stimulation was used to produce gastric ulcers experimentally. Ulceration was induced in rats by exposing the animals to the aggressive attacks of rats treated with 6-hydroxy-dopamine (6-OHDA). Gastric secretion and the effects of autonomic drugs on ulcer formation were investigated. Atropine methylbromide did not significantly inhibit the occurrence of erosions. Phentolamine or hexamethonium bromide significantly inhibited the production of erosions, and combined administration of an anticholinergic agents and alpha-blocking agent led to a complete inhibition, with no notable behavioral change. In case of pylorus ligation, gastric secretion during exposure to attack of 6-OHDA-treated rats was significantly less than that in the controls. We suggest that the sympathetic nervous system plays an important role in the production of gastric erosions, as induced by the methods reported in this study.

Physiological and morphological changes in the gastrointestinal tract induced by hypothalamic intervention: an overview

Neural control and modulation of gastric secretion is well established. The role of the parasympathetic vagal system as a final motor pathway in gastric acid secretion is clearer than the involvement of the sympathetic nervous system. Both portions of the autonomic nervous system, however, appear to play an important role in the pathogenesis of at least experimentally induced gastric erosions. With respect to higher neural control there are numerous reports of hypothalamic effects on gastric secretion, motility, and morphology, yet the results of many of these reports appear equivocal. This ambiguity can be attributed in part to species differences, time course of observations, and differences in stimulation and lesion parameters. However, a mcal description of the sites of central lesions and stimulation. Implications of several of the studies concerning hypothalamic involvement in gastric functions are reviewed and recent methodological advances including neural fiber transection, relatively specific neural cell damage with neurotoxins (e.g., 6-OHDA, kainic acid), histochemistry and intracerebral infusions of gut hormones are suggested as alternative approaches to studying brain-gut relationships.