title: Morphology and somatotopy of the central arborizations of rapidly adapting glabrous skin afferents in the rat lumbar spinal cord.
abstract: The central arborizations in the dorsal horn of the spinal cord of 23 rapidly adapting (RA) A-beta primary afferent neurons innervating different regions of the glabrous skin of the hindpaw were studied by the intra-axonal injection of horseradish peroxidase in adult rats. A total of 284 arbors of the complex, simple, and blind-ending variety were recovered. The arbors of RA afferents innervating the toes, paw pads, and non-pad hindpaw differed from each other in branch pattern and dimensions. The simple and complex arbors, which are both bouton-containing, were distributed mainly in laminae III-V, although some complex arbors projected dorsally into lamina IIi. The hindpaw glabrous skin afferent terminals were located in the lumbar enlargement from caudal L3 to rostral L6. A crude somatotopic organization was observed such that toes 1-5 were represented successively in more caudal positions from mid-L4 to caudal L5. The paw pads were organized in a rostrocaudal sequence moving from the paw pads proximal to toe 1 across the foot to the paw pads proximal to toe 5, from caudal L3 to mid-L5. Non-pad hindpaw afferents were located in caudal L5. Overlap between toe, paw pad and non-pad afferent central fields was present, however, and the central terminals of afferents with non-adjacent peripheral receptive fields were shown to occupy the same region of the dorsal horn.
authors.affiliation: Department of Anatomy and Developmental Biology, University College London, England.
authors.forename: P
authors.initials: P
authors.lastname: Shortland
authors.forename: C J
authors.initials: CJ
authors.lastname: Woolf
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D001931:Brain Mapping / Q000379:methods*; D005260:Female; D005528:Foot / Q000294:innervation; D006614:Hindlimb; D008161:Lumbosacral Region; D008297:Male; D009411:Nerve Endings / Q000648:ultrastructure*; D009475:Neurons, Afferent / Q000648:ultrastructure*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012867:Skin / Q000294:innervation*; D013116:Spinal Cord / Q000502:physiology* / Q000648:ultrastructure; D013997:Time Factors; D014034:Toes / Q000294:innervation