title: Peripheral and central anatomical organization of cutaneous afferent subtypes in a rat nociceptive intersegmental spinal reflex.
abstract: Stimulation of rat segmental dorsal cutaneous nerves (DCNs) evokes the nociceptive intersegmental cutaneus trunci muscle (CTM) reflex. The reflex consists of early and late responses, mediated by Aδ and C fibers, respectively, based on required stimulation strengths, and shows segmental differences in terms of amplitude and duration. We have now investigated whether the peripheral or central anatomy of nociceptive afferent subtypes in different DCNs also vary in a segmental manner. The numbers of different axon subtypes, determined by axon diameter, were analyzed across peripheral DCNs from T6 to L1. The central projections of T7 and T13 DCN afferents were traced using DCN injections of cholera toxin subunit B (CTB) for myelinated A fibers and isolectin B4 (IB4) for unmyelinated C fibers and both labels were quantified in the dorsal horns. Peripheral axon subtype numbers did not differ significantly across DCNs. Centrally, IB4+, but not CTB+, projection areas were different between T7 and T13, consistent with different segmental CTM neurogram responses. At both levels, A fibers projected to deeper layers of the dorsal horn than did C fibers. These termination sites are consistent with both mono- and polysynaptic connections between these afferents and the ascending propriospinal interneurons of the reflex. Also analyzed were the spatial distribution, the synaptic termination, and the glutamatergic transporter profiles of DCN A and C fibers and their relationship to calcitonin gene-related peptide (CGRP) staining in the dorsal horn.
authors.affiliation: Departments of Neurology and Physiology, Emory University School of Medicine, Atlanta, Georgia.
authors.forename: Hyun Joon
authors.identifier: http://orcid.org/0000-0002-6985-0690
authors.initials: HJ
authors.lastname: Lee
authors.affiliation: Biomedical Engineering, Georgia Institute of Technology/Emory University, Atlanta, Georgia.
authors.forename: Jason M
authors.initials: JM
authors.lastname: White
authors.affiliation: Departments of Neurology and Physiology, Emory University School of Medicine, Atlanta, Georgia.
authors.forename: Jumi
authors.initials: J
authors.lastname: Chung
authors.affiliation: Departments of Neurology and Physiology, Emory University School of Medicine, Atlanta, Georgia.|Spinal Cord Injury Clinic, Atlanta Veterans Administration Medical Center, Atlanta, Georgia.
authors.forename: Keith E
authors.initials: KE
authors.lastname: Tansey
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism; D002772:Cholera Toxin / Q000378:metabolism; D005260:Female; D037102:Lectins / Q000378:metabolism; D009413:Nerve Fibers, Myelinated / Q000502:physiology*; D036421:Nerve Fibers, Unmyelinated / Q000502:physiology*; D059225:Nociception / Q000502:physiology*; D051381:Rats; D020318:Rats, Long-Evans; D012018:Reflex / Q000502:physiology*; D012867:Skin / Q000294:innervation*; D013116:Spinal Cord / Q000033:anatomy & histology* / Q000502:physiology; D016708:Synaptophysin / Q000378:metabolism; D050598:Vesicular Glutamate Transport Protein 1 / Q000378:metabolism; D050599:Vesicular Glutamate Transport Protein 2 / Q000378:metabolism
chemical_list: D037102:Lectins; D016708:Synaptophysin; D050598:Vesicular Glutamate Transport Protein 1; D050599:Vesicular Glutamate Transport Protein 2; D002772:Cholera Toxin; D015740:Calcitonin Gene-Related Peptide
keywords: A fibers; C fibers; RRID: AB_10013220; RRID: AB_1113068; RRID: AB_1587626; RRID: AB_2307351; RRID: AB_2307443; RRID: AB_2314660; RRID: AB_2336933; RRID: AB_2340460; RRID: AB_2340472; RRID: AB_2340813; RRID: AB_2340846; RRID: AB_2492289; RRID: AB_887877; RRID: AB_95185; central projection; cholera toxin subunit B (CTB); cutaneus trunci muscle; isolectin B4 (IB4)