Characterization of Dopamine Receptor Subtypes Involved in Experimentally Induced Gastric and Duodenal Ulcers in Rats

Abstract

There are conflicting reports about the role of dopamine in gastric and duodenal ulcers. This investigation was undertaken to characterize the specific subtypes of dopamine receptor involved in gastric and duodenal ulceration. Administration of dopamine D1 agonist fenoldopam and dopamine D2 antagonist sulpiride elicited a significant decrease in acid secretion, total acid output, pepsin output and histamine content in the gastric juice, and reduced ulcer-index values, in pylorus-ligated rats. However, dopamine D1 receptor antagonist SCH 39166 ((-)-trans-6,7,7a,8,9,13b-hexahydro-3-chloro-2-hydroxy-N-methyl-5H -benzo (d) naptho -(2,1-b) azepine) and the D2 receptor agonist quinpirole led to significant augmentation of these parameters compared with respective controls. In the restraint plus water-immersion stress model the score for intraluminal bleeding and the cumulative gastric lesion length was significantly lower for rats treated with fenoldopam and sulpiride. The opposite effects were observed after pretreatment of rats with SCH 39166 and quinpirole. In the cysteamine-induced duodenal ulcer model the mean ulcer area and the score for intensity were significantly lower for fenoldopam and sulpiride and higher for SCH 39166 and quinpirole. Our data suggest that the dopamine D1 and D2 receptors have opposite effects on gastric and duodenal ulcers. Whereas stimulation of dopamine D1 receptors inhibits the formation of gastric and duodenal ulcers, stimulation of dopamine D2 receptors has a pro-ulcerogenic effect.

Antioxidant and Antiinflammatory Activities of Oregano Extract

“…The number of mice in each group was 8. Counting the number of bleeding points was a convenient and appropriate method to estimate the degree of injury in the mouse stomach, because the data obtained with this method showed a significant positive correlation with the data obtained using the ranking method reported by Desai et al 12) in 93 random samples of mice subjected to coldimmobilization stress (γ = 0.77, p < 0.05, F-test). Mouse Model of Contact Hypersensitivity ---Contact hypersensitivity was induced by the following procedures.…”

Pharmacodynamic interaction of Boerhaavia diffusa with omeprazole in experimentally induced ulcers inrats

“…The administration of Indomethacin results in the production of gastric mucosal damage mainly in the glandular portion of the stomach. Indomethacin is known as a prominent inhibitor of prostaglandin synthesis that in turn damages the mucosal barrier; the damage in the mucosal barrier causes the permeation of sodium ions from the mucosa in to the lumen [32].…”

The possible involvement of dopamine D3 receptors in the regulation of gastric emptying in rats

“…It has been shown that dopamine D 4 and dopamine D 1 and/or D 5 receptor mRNA are expressed in the gastrointestinal tract in rats (Hunyady et al, 2001;Vaughan et al, 2000). However, no reports investigating the role of these dopamine receptors (D 1 , D 5 and D 4 ) in the modulation of gastrointestinal motility in rats have been published, though studies have shown that dopamine D 1 and/or D 5 receptors have mucosal protective effects in the gastrointestinal tract (Desai et al, 1999;Mezey et al, 1999) and the dopamine D 4 receptor antagonist clozapine reduces gastric acid secretion (Glavin and Hall, 1994). These results indicate that dopamine D 1 and/or D 5 and D 4 receptors do not play an important role in the process of normal gastric emptying in rats.…”