title: Architecture of vagal motor units controlling striated muscle of esophagus: peripheral elements patterning peristalsis?
abstract: Little is known about the architecture of the vagal motor units that control esophageal striated muscle, in spite of the fact that these units are necessary, and responsible, for peristalsis. The present experiment was designed to characterize the motor neuron projection fields and terminal arbors forming esophageal motor units. Nucleus ambiguus compact formation neurons of the rat were labeled by bilateral intracranial injections of the anterograde tracer dextran biotin. After tracer transport, thoracic and abdominal esophagi were removed and prepared as whole mounts of muscle wall without mucosa or submucosa. Labeled terminal arbors of individual vagal motor neurons (n=78) in the esophageal wall were inventoried, digitized and analyzed morphometrically. The size of individual vagal motor units innervating striated muscle, throughout thoracic and abdominal esophagus, averaged 52 endplates per motor neuron, a value indicative of fine motor control. A majority (77%) of the motor terminal arbors also issued one or more collateral branches that contacted neurons, including nitric oxide synthase-positive neurons, of local myenteric ganglia. Individual motor neuron terminal arbors co-innervated, or supplied endplates in tandem to, both longitudinal and circular muscle fibers in roughly similar proportions (i.e., two endplates to longitudinal for every three endplates to circular fibers). Both the observation that vagal motor unit collaterals project to myenteric ganglia and the fact that individual motor units co-innervate longitudinal and circular muscle layers are consistent with the hypothesis that elements contributing to peristaltic programming inhere, or are "hardwired," in the peripheral architecture of esophageal motor units.
authors.affiliation: Purdue University, Dept. of Psychological Sciences, West Lafayette, IN 47907-2081, United States. Electronic address: powleytl@psych.purdue.edu.
authors.forename: Terry L
authors.initials: TL
authors.lastname: Powley
authors.forename: Ravinder K
authors.initials: RK
authors.lastname: Mittal
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Baronowsky
authors.forename: Cherie N
authors.initials: CN
authors.lastname: Hudson
authors.forename: Felecia N
authors.initials: FN
authors.lastname: Martin
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: McAdams
authors.forename: Jacqueline K
authors.initials: JK
authors.lastname: Mason
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Phillips
mesh_terms: D000818:Animals; D004947:Esophagus / Q000294:innervation* / Q000502:physiology; D008297:Male; D009046:Motor Neurons / Q000166:cytology*; D018482:Muscle, Skeletal / Q000294:innervation*; D009197:Myenteric Plexus / Q000166:cytology; D010528:Peristalsis / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014630:Vagus Nerve / Q000166:cytology*
keywords: Deglutition; Enteric; Motor neuron; Myenteric plexus; NOS neurons; Peristalsis; Swallowing
references.citation: J Anat. 1990 Dec;173:169-76
references.pmid: 2074222
references.citation: Anat Rec. 2001 Jan 1;262(1):41-6
references.pmid: 11146427
references.citation: Neurogastroenterol Motil. 2012 Oct;24(10):e526-37
references.pmid: 22925069
references.citation: Cell Tissue Res. 2003 Mar;311(3):289-97
references.pmid: 12658437
references.citation: Neuropathol Appl Neurobiol. 2010 Apr;36(2):133-56
references.pmid: 20202121
references.citation: Clin Neurophysiol. 2001 Jun;112(6):955-64
references.pmid: 11377252
references.citation: Cell Tissue Res. 1997 Jan;287(1):113-8
references.pmid: 9011386
references.citation: J Anat. 1972 Jul;112(Pt 2):173-84
references.pmid: 5077190
references.citation: Am J Physiol Gastrointest Liver Physiol. 2006 Mar;290(3):G431-8
references.pmid: 16210472
references.citation: Z Zellforsch Mikrosk Anat. 1967;83(1):30-9
references.pmid: 4881661
references.citation: Brain Res. 2011 Aug 29;1409:93-103
references.pmid: 21708380
references.citation: J Comp Neurol. 1995 Oct 2;360(4):705-25
references.pmid: 8801261
references.citation: Physiol Rev. 1983 Apr;63(2):387-436
references.pmid: 6340133
references.citation: Neuroscience. 2008 May 15;153(3):733-50
references.pmid: 18407422
references.citation: Dysphagia. 1990;5(1):35-51
references.pmid: 2202557
references.citation: Physiol Rev. 1980 Jan;60(1):90-142
references.pmid: 6766557
references.citation: Am J Physiol. 1987 Aug;253(2 Pt 2):R361-70
references.pmid: 3618835
references.citation: Brain Res. 2011 Aug 29;1409:42-61
references.pmid: 21762884
references.citation: Histochem Cell Biol. 2005 Feb;123(2):117-30
references.pmid: 15729553
references.citation: Can J Appl Physiol. 1993 Dec;18(4):331-58
references.pmid: 8275048
references.citation: Auton Neurosci. 2013 Oct;177(2):129-42
references.pmid: 23583280
references.citation: J Auton Nerv Syst. 1998 May 28;70(1-2):92-102
references.pmid: 9686909
references.citation: Gastroenterology. 2008 Sep;135(3):796-802
references.pmid: 18675815
references.citation: Anat Rec. 1960 Jun;137:127-34
references.pmid: 24546072
references.citation: Adv Anat Embryol Cell Biol. 2006;185:1-73, back cover
references.pmid: 16573241
references.citation: Laryngoscope. 2002 Apr;112(4):589-602
references.pmid: 12150508