CONTROL OF LOWER ESOPHAGEAL SPHINCTER PRESSURE BY 2 SITES IN DORSAL MOTOR NUCLEUS OF THE VAGUS

Our purpose was to determine the central vagal sites for regulating changes in lower esophageal sphincter (LES) pressure in the cat. Injection of the retrograde tracer, horseradish peroxidase, into the LES resulted in labeling of cells in the dorsal motor nucleus of the vagus (DMV), with the largest number of cells appearing in two areas, one area rostral to obex (1.5-4.0 mm) and one area caudal to obex (-0.5 to -1.5 mm). In alpha-chloralose-anesthetized cats, L-glutamic acid was microinjected into these areas and LES pressure, intragastric pressure, and stomach motility were monitored. Microinjection of L-glutamic acid into the rostral area resulted in significant increases in LES pressure (18.6 +/- 4.9 mmHg; P < 0.05), pyloric motility (baseline minute motility increased from 5.7 +/- 2.2 to 14.5 +/- 3.9 postinjection; P < 0.05) and stomach pressure (baseline of 16.9 +/- 2.3 mmHg increased to 23.8 +/- 3.7 mmHg postinjection; P < 0.05). Microinjection of L-glutamic acid into the caudal area resulted in significant decreases in LES pressure (-14.3 +/- 5.8 mmHg; P < 0.05) and intragastric pressure (-7.5 +/- 2.2 mmHg; P < 0.05) with no significant changes in pyloric motility. Ipsilateral vagotomy abolished both sets of responses. These data indicate that excitatory and inhibitory control of LES and intragastric pressure are mediated by vagal efferent neurons located in two distinct sites in the DMV.