Human esophageal response to rapid swallowing: muscle refractory period or neural inhibition?

The peristaltic response of the normal human esophagus to 10 repeated water swallows separated by varying time intervals (5, 10, 15, 20, and 30 s) between swallows was studied. Pressures measured during the shorter time intervals were of lower amplitude than those at 30-s swallowing intervals throughout the esophagus, with the distal esophagus showing the greatest effect. Frequency of peristalsis was decreased throughout the esophagus with rapid swallowing, especially distally at the 5- and 10-s time intervals. There was no significant change in wave velocity or duration at these time intervals. These data suggest that there is a refractory period in the distal (smooth muscle) esophagus. A series of paired swallows separated by 5 s resulted in a significant decrease in amplitude of the first swallow, and this was more marked in the distal esophagus. These data indicate that there is an inhibition of the progression of peristalsis by a subsequent swallow, probably through a neural mechanism. These studies show that repeated liquid swallows may effect peristalsis by two mechanisms: refractoriness of esophageal smooth muscle and a neural inhibitory discharge.