The pharyngeal phase of swallowing controls deglutitive inhibition

The goal of this study was to determine which phase of swallowing causes deglutitive inhibition (DI). DI is inhibition of ongoing peristalsis by a new swallow. Pharynx and esophagus of decerebrate cats (<i>n =</i> 25) were instrumented to record esophageal peristalsis. Injecting saline into pharynx or esophagus activated primary (pharyngeal and esophageal phases) peristalsis repeatedly and randomly, or secondary (esophageal phase) peristalsis once, respectively. When a new primary peristalsis occurred during ongoing primary peristalsis, the occurrence of ongoing esophageal peristalsis was blocked when it was 1-10 cm from upper esophageal sphincter, then secondary peristalsis occurred 1.3 ± 0.1 s (<i>n =</i> 22) later at same location. This esophageal blockade occurred almost simultaneously [0.15 ± 0.01 s (<i>n =</i> 17) before] with activation of thyropharyngeus activation during the new pharyngeal phase. When ongoing primary peristalsis was at or below 13 cm from upper esophageal sphincter, the magnitude of primary esophageal peristalsis significantly decreased (102 ± 14 vs. 49 ± 8 mm Hg, <i>n =</i> 8, <i>P</i> < 0.01) during the new pharyngeal phase, but peristaltic progression was not altered. DI had same effects on secondary peristalsis. DI of ongoing peristalsis in distal esophagus occurred before or without new esophageal phase in every case (21 cases, <i>n =</i> 9), except one. DI is central inhibition of ongoing esophageal phase of swallowing by the new pharyngeal phase as short-term cessation of striated muscle peristalsis and longer-term reduction in smooth muscle peristaltic magnitude. Esophageal or oral phase of swallowing does not cause DI.<b>NEW & NOTEWORTHY</b> Deglutitive inhibition is caused by central inhibition of ongoing esophageal phase of swallowing during the new pharyngeal phase by short-term cessation of striated muscle peristalsis and longer-term reduction in smooth muscle peristaltic magnitude. The esophageal or oral phase of swallowing does not cause deglutitive inhibition. Deglutitive inhibition is pharyngeal phase central inhibition of the esophageal phase of swallowing.