Effect of first part of duodenum on gastric emptying in dogs: response to acid, fat, glucose, and neural blockade
Cooke, A.R.; Clark, E.D.
Gastroenterology 70(4): 550-555
1976
ISSN/ISBN: 0016-5085 PMID: 1254139 Document Number: 99999
In 5 dogs, each with a gastric and a duodenal fistula (5 cm distal to the pylorus), a test meal was instilled into the stomach and collected at 1- or 2-min intervals for 10 or 20 min from the duodenal fistula. As the test meal emptied from the stomach it bathed the first 5 cm of duodenum and thus stimulated the appropriate receptor. A Foley catheter with an inflated balloon prevented passage into the lower part of the duodenum. Test meals of hypertonic glucose, 15%, or sodium oleate 20 or 80 mmolar emptied at the same rate as water when allowed to bathe the first 5 cm of duodenum, whereas test meals of 100 mmolar HCl were slowed. In studies with neural blocking agents, the emptying of water meals was slowed with subcutaneous atropine sulphate 0.03 or 0.15 mg/kg, intravenous hexamethonium chloride 10 mg/kg, and norepinephrine bitartrate 0.04 mg/kg. The emptying of 100-120 mmolar HCl meals was slowed by subcutaneous atropine sulphate 0.03 or 0.15 mg/kg, intravenous norepinephrine bitartrate 0.04 mg/kg, and the intravenous alpha -receptor blocking agents phenoxybenzamine HCl 2 mg/kg and phentolamine 2 mg/kg, was unaffected by intravenous hexamethonium chloride 10 mg/kg, and was unchanged or slightly slowed by the beta -receptor blocker propranolol at 1.0 or 2.0 mg/kg, respectively. In contrast, acid test meals were emptied at the same rate as water when dogs were treated with intravenous guanethidine monosulphate 2 mg/kg or intramuscular reserpine 1 mg/kg, indicating that the acid inhibition was mediated by an adrenergic mechanism. The emptying of water meals was unchanged by these 2 drugs. It is suggested that the first 5 cm of duodenum contain receptors for inhibition of emptying of acid but not for fat or hypertonic glucose. The neural blocking studies indicate that the inhibitory effect of acid in the first part of the duodenum is an adrenergic mechanism which appears to be neither alpha - nor beta -receptor-mediated.