Relation between electrical and mechanical activity in esophageal smooth muscle

Abstract

Experiments were performed in anesthetized opossums. Electrical and mechanical activity was recorded simultaneously from the esophageal body at 5, 3 and 1 cm above the lower esophageal sphincter (LES). Esophageal responses were evoked by electrical stimulation of vagal efferents or by induced swallowing. Electrical and mechanical activity was associated in 86% and dissociated in 14% of the 1200 responses examined. The frequency of dissociation was dependent on the site in the esophagus and the frequency of vagal efferent stimulation (P < 0.05). The interval between the onset of electrical and mechanical events, called electromechanical delay had a regional gradient: 5 cm above LES > 3 cm > 1 cm (P < 0.01). This delay was also dependent on the frequency of stimulation. The amplitude of spike burst and the number of spikes in a burst closely correlated with the amplitude of contraction. Electromechanical responses and dissociations are evidently dependent on the regional level in the esophagus and the frequency of vagal stimulation.