[The effects of exogenous and endogenous dopamine on the gastric microcirculation and their action sites in rat stomach].
The effect of exogenous and endogenous dopamine on the gastric microcirculation and their action sites on stomach were investigated by laser Doppler flowmetry, histochemistry, electron microscopy and radioautography. The effects of graded doses of dopamine on the gastric mucosal blood flow were different from those on the systemic blood flow, implying that there may exist a dopaminergic control of gastric mucosal blood flow independent from the systemic circulation. By histochemical observations of the horseradish peroxidase (HRP) infused preparations, HRP was found to be distributed mainly to the arterioles and venules at the base of the gastric mucosa with a high dose of dopamine which may contributed to open the arterio-venular shunt either at the base of mucosa or in the submucosa. Pretreatment with monoamine oxidase inhibitor and/or 6-hydroxydopamine caused changes in the levels of endogenous catecholamine (dopamine, noradrenaline and adrenaline) in the stomach wall. An imbalanced catecholamine in the stomach wall, particularly an increase in DA, decreased gastric mucosal blood flow. Radioautographic studies revealed that D1-receptors are located mainly on the arterioles in the lower part of the mucosa and submucosa, while D2-receptors are located mainly on the muscularis mucosae and on the collecting venules. Tyrosine hydroxylase (TH) positive nerve fibers possibly corresponding to the dopaminergic fiber were evident in the vicinity to the arterioles, venules, and muscularis mucosae. Some TH-positive fibers were extended to the true capillaries in the mucosa. Dopamine beta-hydroxylase positive fibers were noted near the arterioles and venules both in the submucosa and the lower portion of mucosal layer. Based on the above results, the dopaminergic mechanisms are considered to be involved in the regulation of the gastric mucosal microcirculation through the dopaminergic nerves.
Nishizaki
Y
Y
Department of Internal Medicine, School of Medicine, Keio University.
D000818:Animals; D001012:Aorta, Abdominal / Q000502:physiology; D001345:Autoradiography; D002395:Catecholamines / Q000502:physiology; D004298:Dopamine / Q000494:pharmacology / Q000502:physiology*; D005753:Gastric Mucosa / Q000098:blood supply* / Q000187:drug effects / Q000378:metabolism; D017078:Laser-Doppler Flowmetry; D008297:Male; D008833:Microcirculation / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D012039:Regional Blood Flow
D002395:Catecholamines; D004298:Dopamine