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Effects of metiamide and propranolol on gastric secretion in anesthetized dogs
Abstract:
The effects of metiamide, a histamine H2-receptor antagonist, and propranolol, a beta-adrenergic blocking agent, on gastric secretion were studied in anesthetized dogs. Metiamide, 1.45 mg/kg i.v., markedly inhibited the gastric secretion induced by a continuous i.v. infusion of tetragastrin (8 microng/kg-hr), histamine dihydrochloride (160 microng/kg-hr), or methacholine bromide (100 microng/kg-hr). Propranolol 0.5 or 1.0 mg/kg i.v. produced a significant potentiation of tetragastrin-induced gastric secretion but no influence of the secretion induced by methacholine. Propranolol at 5 or 10 mg/kg i.v. produced a slight reduction of the tetragastrin-induced secretion and a significant reduction of methacholine-induced secretion. Histamine-induced gastric secretion was not affected by propranolol at either 1 and 10 mg/kg i.v. These findings lend support to the hypothesis that interactions among histamine, gastrin and acetylcholine receptors do occur though the degree would not be the same in all directions.
Insights
Metiamide (H2-receptor antagonist) inhibited gastric secretion. Propranolol (beta-blocker) had mixed effects, potentiating or reducing secretion depending on the stimulant, suggesting receptor interactions.
Area of Science:
- Pharmacology
- Gastroenterology
- Physiology
Background:
- Histamine H2-receptor antagonists and beta-adrenergic blockers are crucial in modulating physiological processes.
- Gastric secretion is regulated by complex interactions involving various signaling pathways.
Purpose of the Study:
- To investigate the effects of metiamide and propranolol on gastric secretion in anesthetized dogs.
- To explore potential interactions between histamine, gastrin, and acetylcholine pathways in gastric acid production.
Main Methods:
- Administered metiamide (histamine H2-receptor antagonist) and propranolol (beta-adrenergic blocking agent) intravenously to anesthetized dogs.
- Stimulated gastric secretion using tetragastrin, histamine dihydrochloride, and methacholine bromide.
- Quantified changes in gastric secretion in response to drug administration and secretagogue stimulation.
Main Results:
- Metiamide significantly inhibited gastric secretion induced by tetragastrin, histamine, and methacholine.
- Low-dose propranolol potentiated tetragastrin-induced secretion but did not affect methacholine-induced secretion.
- High-dose propranolol reduced tetragastrin and methacholine-induced secretion, while histamine-induced secretion remained unaffected.
Conclusions:
- Findings support the hypothesis of receptor interactions among histamine, gastrin, and acetylcholine pathways.
- The degree of interaction between these receptor systems in regulating gastric secretion is complex and direction-dependent.