Effects of Biogenic Monoamines and Precursors on Stress Ulcers and Secretion in Stomach

Abstract

Abstract-Effectsof biogenic monoamines and their precursors on stress ulcers and secretion in stomach were investigated herein. Norepinephrine, 5-HT and their precursors prevented formation of stress ulcer at any level of endogenous monoamines in reserpine or iproniazid-treated rats. These same agents did not affect the stress induced decrease in the output of PSB but increased the pH value of gastric juice.It was reported that experimental ulcers were produced in the cat gastrointestinal tract by small doses of reserpine followed by electrical shock or hypothalamic stimulation and that the mechanism would involve a decrease in central monoamine level (1-6). It was also shown that reserpine or reserpine-like drugs caused gastric hemorrhage by a mechanism which involved release of catecholamines or serotonin (7,8).Recently, the present authors have demonstrated that formation of gastric ulcer in rats treated with a combination of reserpine and stress is due to endogenously liberated monoamines and that the decrease in gastric monoamine level prevents formation of the stress ulcer (9). Further studies have shown that the output of injected Pontamine Sky Blue 6BX (PSB) in the gastric juice is decreased by stress, probably due to sustained con tractions of gastric mucosal vessels resulted from liberation of monoamines and that there is a reciprocal relationship between the production of stress ulcer and the output of PSB (10).The present experiments were carried out to determine effects of exogenously admin istered monoamines and precursors on the production of stress ulcer at various level of endogenous monoamines as well as the effects on the output of PSB in the stomach, in order to correlate the two parameters.MATERIALS AND METHODS Stress ulcer: As described previously by Takagi and Okabe (11), male rats of Donryu strain (220-260 g) were immersed into a water bath at 23°C for 7 hr to the level of xiphoid . The animals were then sacrificed, the isolated stomach was inflated with about 10 ml water and placed in 0.5% formalin for 5 min, according to Brodie et al. (12). After washing, the stomach was incised along the greater curvature. Ulcerative changes were scored and expressed as ulcer index, according to grade and number as described by Takagi and Okabe (11).Determination of output of PSB (13) : Male Donryu strain rats (about 250 g) were