Pharyngeal, esophageal, and proximal gastric responses associated with vomiting

The motor activities of the pharynx, esophagus, and proximal stomach associated with vomiting were characterized and quantified in 25 awake chronically instrumented dogs. These motor events were correlated temporally with motor responses of the gastrointestinal and respiratory tracts. Vomiting was stimulated by apomorphine or UK-14304, and motor activities of striated and smooth muscles were recorded by electromyography and strain-gauge transducers, respectively. We found responses that began 1) before retching: increased swallow frequency, relaxation of the lower esophageal sphincter (LES) and proximal stomach, and tonic contraction of the cricopharyngeus and cervical esophagus; 2) during retching: rhythmic relaxation and contraction of the pharynx and cervical esophagus 180 degrees out of phase with retching; and 3) during vomitus expulsion: relaxation of the pharynx and cervical esophagus but strong contraction of the geniohyoideus and a retrograde contraction of the cervical esophagus and pharynx. The increased pharyngoesophageal tone occurred in an all-or-none fashion independent of vomiting or the gastrointestinal correlates of vomiting. Cervical vagal blockade increased swallow frequency but did not alter the other pharyngoesophageal responses associated with vomiting. We concluded that the motor events of the pharynx and esophagus play a significant role in gastrooral evacuation during vomiting and that these motor events (except LES relaxation) are not controlled by subnodose vagal pathways.