title: Spinal afferent nerve endings in visceral organs: recent advances.
abstract: Spinal afferent neurons play a major role in detection and transduction of painful stimuli from internal (visceral) organs. Recent technical advances have made it possible to visualize the endings of spinal afferent axons in visceral organs. Although it is well known that the sensory nerve cell bodies of spinal afferents reside within dorsal root ganglia (DRG), identifying their endings in internal organs has been especially challenging because of a lack of techniques to distinguish them from endings of other extrinsic and intrinsic neurons (sympathetic, parasympathetic, and enteric). We recently developed a surgical approach in live mice that allows selective labeling of spinal afferent axons and their endings, revealing a diverse array of different types of varicose and nonvaricose terminals in visceral organs, particularly the large intestine. In total, 13 different morphological types of endings were distinguished in the mouse distal large intestine, originating from lumbosacral DRG. Interestingly, the stomach, esophagus, bladder, and uterus had less diversity in their types of spinal afferent endings. Taken together, spinal afferent endings (at least in the large intestine) appear to display greater morphological diversity than vagal afferent endings that have previously been extensively studied. We discuss some of the new insights that these findings provide.
authors.affiliation: Discipline of Human Physiology and Centre for Neuroscience, School of Medicine, Flinders University of South Australia, Adelaide, Australia nicholas.spencer@flinders.edu.au.
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 of South Australia, Adelaide, Australia.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Zagorodnyuk
authors.affiliation: Discipline of Human Physiology and Centre for Neuroscience, School of Medicine, Flinders University of South Australia, Adelaide, Australia.
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Brookes
authors.affiliation: Discipline of Human Physiology and Centre for Neuroscience, School of Medicine, Flinders University of South Australia, Adelaide, Australia.
authors.forename: Tim
authors.identifier: 0000-0002-3747-140X
authors.initials: T
authors.lastname: Hibberd
mesh_terms: D000818:Animals; D005727:Ganglia, Spinal / Q000378:metabolism / Q000502:physiology*; D007422:Intestines / Q000294:innervation; D051379:Mice; D009411:Nerve Endings / Q000378:metabolism / Q000502:physiology*; D017833:Visceral Afferents / Q000378:metabolism / Q000502:physiology*
keywords: dorsal root ganglia; nociception; pain; spinal afferent; visceral afferent