title: Different types of spinal afferent nerve endings in stomach and esophagus identified by anterograde tracing from dorsal root ganglia.
abstract: In visceral organs of mammals, most noxious (painful) stimuli as well as innocuous stimuli are detected by spinal afferent neurons, whose cell bodies lie in dorsal root ganglia (DRGs). One of the major unresolved questions is the location, morphology, and neurochemistry of the nerve endings of spinal afferents that actually detect these stimuli in the viscera. In the upper gastrointestinal (GI) tract, there have been many anterograde tracing studies of vagal afferent endings, but none on spinal afferent endings. Recently, we developed a technique that now provides selective labeling of only spinal afferents. We used this approach to identify spinal afferent nerve endings in the upper GI tract of mice. Animals were anesthetized, and injections of dextran-amine were made into thoracic DRGs (T8-T12). Seven days post surgery, mice were euthanized, and the stomach and esophagus were removed, fixed, and stained for calcitonin gene-related peptide (CGRP). Spinal afferent axons were identified that ramified extensively through many rows of myenteric ganglia and formed nerve endings in discrete anatomical layers. Most commonly, intraganglionic varicose endings (IGVEs) were identified in myenteric ganglia of the stomach and varicose simple-type endings in the circular muscle and mucosa. Less commonly, nerve endings were identified in internodal strands, blood vessels, submucosal ganglia, and longitudinal muscle. In the esophagus, only IGVEs were identified in myenteric ganglia. No intraganglionic lamellar endings (IGLEs) were identified in the stomach or esophagus. We present the first identification of spinal afferent endings in the upper GI tract. Eight distinct types of spinal afferent endings were identified in the stomach, and most of them were CGRP immunoreactive. J. Comp. Neurol. 524:3064-3083, 2016. © 2016 Wiley Periodicals, Inc.
authors.affiliation: Discipline of Human Physiology and Centre for Neuroscience, School of Medicine, Flinders University, Adelaide, 5001, South Australia, Australia.
authors.forename: Nick J
authors.initials: NJ
authors.lastname: Spencer
authors.affiliation: Discipline of Human Physiology and Centre for Neuroscience, School of Medicine, Flinders University, Adelaide, 5001, South Australia, Australia.
authors.forename: Melinda
authors.initials: M
authors.lastname: Kyloh
authors.affiliation: Discipline of Physiology, School of Medicine, University of Adelaide, Adelaide, 5000, South Australia, Australia.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Beckett
authors.affiliation: Discipline of Human Physiology and Centre for Neuroscience, School of Medicine, Flinders University, Adelaide, 5001, South Australia, Australia.
authors.forename: Simon
authors.initials: S
authors.lastname: Brookes
authors.affiliation: Discipline of Human Physiology and Centre for Neuroscience, School of Medicine, Flinders University, Adelaide, 5001, South Australia, Australia.
authors.forename: Tim
authors.initials: T
authors.lastname: Hibberd
mesh_terms: D000344:Afferent Pathways / Q000166:cytology; D000818:Animals; D004947:Esophagus / Q000166:cytology* / Q000294:innervation*; D005260:Female; D005727:Ganglia, Spinal / Q000166:cytology*; D007150:Immunohistochemistry; D008297:Male; D008810:Mice, Inbred C57BL; D009092:Mucous Membrane / Q000166:cytology / Q000294:innervation; D056325:Neuronal Tract-Tracers; D009475:Neurons, Afferent / Q000166:cytology*; D013270:Stomach / Q000166:cytology* / Q000294:innervation*; D013904:Thoracic Vertebrae
chemical_list: D056325:Neuronal Tract-Tracers
keywords: RRID: AB_2314156; dorsal root ganglia (DRGs); esophagus; nociception; pain; primary afferent; sensory nerve; spinal afferent; stomach; viscera