The role of adrenergic receptors in the regulation of gastric motility in the rat.

Gastric motility was investigated under the effect of adrenergic receptor agonist and antagonist substances in albino rats of both sexes and weighing 150 to 180 g. Gastric evacuation was studied, after introducing 2 ml/100 g of Novobarium suspension in the stomach, by radioscopy and radiography. Epinephrine (Tonogen) was found to inhibit gastric motility, this inhibition being effective even after pylorotomy. The dominantly alpha adrenergic agonist phenylephrine (Sympathomim) had not any effect; the alpha blocker phenoxybenzamine (Dibenzyline) slightly depressed gastric evaluation. A marked inhibitory influence was noted with stimulating the beta receptors by isoproterenol (Prophylon), while propranolol (Inderal) slightly accelerated gastric evacuation by blocking beta receptors. A pretreatment by phenoxybenzamine of the animals did not affect epinephrine influence whereas a pretreatment by propranolol completely abolished the inhibitory effect of epinephrine on gastric motility. These results suggest the presence of a slight beta receptor tone in gastric motility at rest, and indicate further that epinephrine exerts its inhibitory effect on gastric motility via adrenergic beta receptors.