Recognition of a pharyngo-oesophageal sphincter inhibitory reflex in dogs and its role in deglutition.

The present study describes the 'pharyngo-oesophageal sphincter inhibitory reflex' and its clinical significance. The study was performed on twelve anaesthetized dogs. A balloon-tipped catheter was placed within the pharyngo-oesophageal sphincter (POS) and another in the pharynx. The POS response to distension of the pharynx with a balloon filled with 2, 4 or 6 ml of water was recorded before and after application of local anaesthetic to the POS, and after successive section of the anatomical constituents of the POS. Upon pharyngeal distension, POS pressure was reduced; the greater the distension, the greater the pressure reduction. The anaesthetized POS did not respond to pharyngeal distension. Section of the cricopharyngeus muscle did not influence the resting POS pressure or the POS response to pharyngeal distension. The POS pressure dropped significantly (P < 0.0001) and was unresponsive to pharyngeal distension after section of both the cricopharyngeus muscle and the oesophageal circular muscle bundles. This shows that the cricopharyngeus muscle is not involved in the upper oesophagus sphincter mechanism.