Abstract
Depending upon the origin of the stimuli which signal the secretion of gastric juice, three distinct aspects of secretion have been elucidated: the cephalic, gastric and intestinal. The efferent cholinergic mechanism is involved in the cephalic phase of gastic secretion, because cutting of the vagi just above the stomach completely eliminates the secretion. On the other hand, participation of gastrin to the gastric phase of secretion and its chemical structure have recently been demonstrated (1). However, the gastric secretion mechanism is more complicated. It is possible that the intact cholinergic innervation (2) and the presence of endogenous monoamines in the gastric wall (3) are the prerequisite to the gastrin-induced gastric secretion. There are controversial reports regarding the effect of adrenergic stimuli on the gastric secretion (4-7). In the mucous membrane of the glandular portion of the rat stomach, dopa-decarboxylase activity is high (8), but the high activity is not explained by the number of mast cells (9) and adrenergic nerves (10, 11) in the gastric mucosa. The distribution of the enterochromaffin cells is also different from that of gastric dopa decarboxylase (8). Intraperitoneal injection of dopa or 5-hydroxytryptophan (5-HTP) to rats causes a marked increase in the concentration of dopamine and 5-hydroxytryptamine (5-HT) in the gastric mucosa, and the amines are located to an enterochromaffin-like cell system in the pyloric part of the gastric mucosa (8). However, the physiological significance of the uptake and decarboxylation of dopa or 5-HT remains to be settled. In the present experiments the distribution of the endogenous monoamines in the structures of the gastric wall of the rat was studied using a formaldehyde fluorescence technique (12, 13). The temporal changes of the monoamine fluorescence were also followed in the course of formation of the gastric ulcers in the Shay rat and the restraint, cold-exposed rat.
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