The mechanism of action of gastrin on the lower esophageal sphincter.

Gastrin I or pentagastrin caused contraction of the lowe esophageal sphincter in anesthetized oppossums. The contraction was not modified, either qualitatively or quantitatively, by 30 or 1000 mug per kg atropine pretreatment. Moreover, neural block with tetrodotoxin did not influence the effect of gastrin on the sphincter pressure. H2 receptor antagonist, metiamide, did not modify the magnitude of the contractile response of the lower esophageal sphincter to gastrin I. These studies show: a) gastrin does not cause sphincter contraction by stimulating cholinergic neurons: and b) gastrin does not exert an inhibitory effect on the sponcter pressure by stimulating H2 receptors. We suggest that gastrin may contract the lower esophageal sphincter by a direct action on the sphincter muscle.