AJP - Gastrointestinal and Liver Physiology, Vol 259, Issue 2 245-G251, Copyright © 1990 by American Physiological Society
Determinants of upper esophageal sphincter pressure in dogs
P. Jacob, P. J. Kahrilas, G. Herzon and B. McLaughlin
Department of Medicine, Northwestern University Medical School, Chicago, Illinois.
Chronic experiments were done on six dogs fitted with EMG electrodes on
pharyngeal and esophageal musculature. Electromyographic activity of the
cricopharyngeus was recorded in awake and sedated animals with and without
manometric recordings as well as during esophageal distension. Intraluminal
upper esophageal sphincter (UES) pressure had two distinct components;
active contraction accompanied by cricopharyngeal EMG activity and passive
elasticity that persisted in the absence of EMG activity. Between swallows,
the cricopharyngeal EMG activity patterns observed were of either tonic
activity, no activity, or phasic activity with inspiratory bursts. The
activity level was markedly affected by anesthesia, phonating, whining,
panting, level of alertness, or changes in head posture. A brisk UES
contraction was elicited in response to passage of the manometric assembly
and to intraesophageal balloon distension. Persistent EMG augmentation
after stationing of the manometric sensor suggested that intraluminal
manometry tends to exaggerate resting sphincter pressure. We conclude that
electrical activity of the cricopharyngeus, and by inference UES pressure,
is markedly affected by many variables that are difficult to control during
clinical or experimental determinations of UES pressure.
