Abstract
Summary
The effect of vasoactive intestinal polypeptide (VIP) on the lower esoph-ageal sphincter (LES) was studied in anesthetized opossums. Intravenous administration of VIP caused a dose-related fall in LES pressure. A dose of 8 μg/kg produced a “maximal” fall of 36.8 ± 2.9 mm Hg (80.5 ± 4.5%) in sphincter pressure. The effect of VIP (8 μg/kg) was not antagonized by tetro-dotoxin in the doses which antagonized neural activity in the LES. β-Adrenergic antagonist, propranolol, also failed to antagonize this inhibitory effect of VIP. These studies show that VIP exerts an inhibitory effect on the LES. Moreover, this inhibitory effect may be due to a direct action on the sphincter muscle.
The authors thank Elizabeth Howard and Kim Bain for technical assistance and Jean Harber for preparation of the manuscript.
These studies were supported by Grant AM18403 from the National Institute of Arthritis, Metabolism, and Digestive Diseases, and Center Award HL14187.
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