title: Dorsal motor nucleus of the vagus: a site for evoking simultaneous changes in crural diaphragm activity, lower esophageal sphincter pressure, and fundus tone.
abstract: The sphincter mechanism at the esophagogastric junction includes smooth muscle of the lower esophagus and skeletal muscle of the crural diaphragm (CD). Smooth muscle is known to be under the control of the dorsal motor nucleus of the vagus (DMV), while central nervous system (CNS) control of the CD is unknown. The main purposes of our study were to determine the CNS site that controls the CD and whether simultaneous changes in lower esophageal sphincter (LES) pressure and CD activity occur when this site is activated. Experiments were performed on anesthetized male ferrets whose LES pressure, CD activity, and fundus tone were monitored. To activate DMV neurons, L-glutamate was microinjected unilaterally into the DMV at three areas: intermediate, rostral, and caudal. Stimulation of the intermediate DMV decreased CD activity (-4.8 +/- 0.1 bursts/min and -0.3 +/- 0.01 mV) and LES pressure (-13.2 +/- 2.0 mmHg; n = 9). Stimulation of this brain site also produced an increase in fundus tone. Stimulation of the rostral DMV elicited increases in the activity of all three target organs (n = 5). Stimulation of the caudal DMV had no effect on the CD but did decrease both LES pressure and fundus tone (n = 5). All changes in LES pressure, fundus tone, and some DMV-induced changes in CD activity (i.e., bursts/min) were prevented by ipsilateral vagotomy. Our data indicate that simultaneous changes in activity of esophagogastric sphincters and fundus tone occur from rostral and intermediate areas of the DMV and that these changes are largely mediated by efferent vagus nerves.
authors.affiliation: Department of Pharmacology, Georgetown University Medical Center, Washington, DC 20007, USA.
authors.forename: Mark
authors.initials: M
authors.lastname: Niedringhaus
authors.forename: Patrick G
authors.initials: PG
authors.lastname: Jackson
authors.forename: Stephen R T
authors.initials: SR
authors.lastname: Evans
authors.forename: Joseph G
authors.initials: JG
authors.lastname: Verbalis
authors.forename: Richard A
authors.initials: RA
authors.lastname: Gillis
authors.forename: Niaz
authors.initials: N
authors.lastname: Sahibzada
mesh_terms: D000818:Animals; D003964:Diaphragm / Q000294:innervation / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D049630:Esophageal Sphincter, Lower / Q000294:innervation / Q000502:physiology*; D005289:Ferrets; D005748:Gastric Fundus / Q000294:innervation / Q000502:physiology*; D018698:Glutamic Acid / Q000494:pharmacology; D008297:Male; D008845:Microinjections; D009046:Motor Neurons / Q000187:drug effects / Q000502:physiology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D014630:Vagus Nerve / Q000187:drug effects / Q000502:physiology*; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D014660:Vasoactive Intestinal Peptide; D018698:Glutamic Acid; D019331:NG-Nitroarginine Methyl Ester