The effect of differential vagal nerve cooling on feline esophageal function

Studies were performed on four cats to examine the effects of differential vagal nerve cold blockade on the upper esophageal sphincter, esophageal peristalsis, and swallow-induced lower esophageal sphincter relaxation. Reversible vagal nerve blockade was accomplished by cooling the cervical nerve trunks. Pressures were measured using multi-lumen manometry tubes. Upper esophageal sphincter pressure (resting and response to intraesophageal balloon distention), primary peristalsis, secondary peristalsis induced by intraesophageal balloon distention, and swallow-induced lower esophageal sphincter relaxation were evaluated at each temperature level, with vagal cooling from 20 degrees C to 0 degree C by 0.5 degree C decrements. Primary and secondary peristalsis were abolished at the same temperature. Swallow-induced lower esophageal sphincter relaxation was abolished at the same temperature that peristalsis was abolished. Upper esophageal sphincter pressure decreased by at least 25% at the same temperature that secondary peristalsis was abolished. Balloon distention-induced increase in upper esophageal sphincter pressure was not abolished prior to the decrease in resting pressure and, in the majority of experiments, was not abolished at any time during differential cooling. Prolonged complete vagal nerve blockade experiments demonstrated transient abolition and then return of balloon distention-induced reflex upper esophageal sphincter contraction. We conclude that: 1) differential vagal cooling does not allow separation of the contribution of different vagal fibres such as afferent vs efferent or excitatory versus inhibitory; 2) there is dual afferent innervation from the proximal cervical esophagus, allowing persistence of intraesophageal balloon distention-induced upper esophageal sphincter contraction during prolonged vagal cervical trunk blockade.