Barium Stimulation of Esophageal Smooth Muscle ∗

Abstract

Summary

This study reports the effect of BaCl₂ on circular smooth muscle from the distal esophagus of the cat. The magnitude of the contractile response is dose-related; the threshold concentration varies from 5 × 10^-5 to 5 × 10^-4 gm/ml and irreversible contracture occurs at concentrations of 5 × 10^-3 gm/ml or greater. The dose-response curve is not affected by atropine, hexamethonium, nicotine or the β-adrenergic stimulant, dl-isoproterenol. Thus, the response to barium is the result of a direct action on muscle rather than an indirect action through stimulation of motor elements of the esophageal intramural plexuses.