Effect of bilateral vagosympathetic nerve blockade on response of the dog upper esophageal sphincter (UES) to intraesophageal distention and acid.

The present study in dogs was performed to elucidate (a) the upper esophageal sphincter responses to intraesophageal distention and acid perfusion and (b) the effect of bilateral nerve blockade on these responses. Balloon distention (5-40 cm3) at 5, 10, 15, and 20 cm below the sphincter produced up to a 400% increase in sphincter pressure. The threshold for this response increased, and the maximum sphincter response decreased as distention was performed more distally in the esophagus. Perfusion of acid (0.1-0.4 N HCl) at the level of the upper esophageal sphincter and at 5, 10, and 15 cm below, produced a similar increase in sphincter pressure. The maximum response to acid occurred on perfusion at the sphincter and the response decreased progressively with perfusion distally. Bilateral nerve blockade produced (a) no change in resting sphincter pressure or in the sphincter response to swallowing, (b) a partial reduction in the maximum sphincter response to distention, and (c) abolition of the response to acid. A significant portion of the afferent pathway for the response of the upper esophageal sphincter to distention and virtually all the afferent pathways for the response to acid are carried in the vagosympathetic trunks presumably via the recurrent laryngeal nerves.