title: Characteristics of sensory DRG neurons innervating the lumbar facet joints in rats.
abstract: The rat L5/6 facet joint, from which low-back pain can originate, is multisegmentally innervated from the L1 to L5 dorsal root ganglions (DRGs). Sensory fibers from the L1 and L2 DRGs are reported to non-segmentally innervate the paravertebral sympathetic trunks, whilst those from the L3 to L5 DRGs segmentally innervate the L5/6 facet joint. In the current study, characteristics of sensory DRG neurons innervating the L5/6 facet joint were investigated in rats, using a retrograde neurotransport method, lectin affinity- and immuno-histochemistry. We used four markers: (1) calcitonin gene-related peptide (CGRP) as a marker of small peptide containing neurons, (2) the glycoprotein binding the isolectin from Griffonia simplicifolia (IB4) or (3 the purinergic P2X(3) receptor for small, non-peptide containing neurons, and (4) neurofilament 200 (NF200) for small and large myelinated fibers. IB4-binding and CGRP and P2X(3) receptor containing neurons are typically involved in pain sensation, whereas NF200 is associated with pain and proprioception. Neurons innervating the L5/6 facet joints, retrogradely-labeled with fluoro-gold (FG), were distributed throughout DRGs from L1 to L5. Of FG-labeled neurons, the ratios of NF200 immunoreactive (IR) neurons and CGRP-IR neurons were 37% and 35% respectively. The ratio of IB4-binding and P2X(3) receptor-IR neurons was 10%, significantly less than the ratio of CGRP-IR neurons to FG-labeled neurons. The ratios of IB4-binding and P2X(3) receptor-IR neurons were significantly higher, and that of CGRP-IR neurons was significantly less in L1 and L2 DRGs than those in L3, L4 or L5 DRGs. Under physiological conditions in rats, DRG neurons transmit several types of sensations, such as proprioception or nociception of the facet joint. Most neurons transmitting pain are CGRP-IR peptide-containing neurons. They may have a more significant role in pain sensation in the facets via peptidergic DRG neurons.
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8670, Japan.
authors.forename: Tetsuhiro
authors.initials: T
authors.lastname: Ishikawa
authors.forename: Masayuki
authors.initials: M
authors.lastname: Miyagi
authors.forename: Seiji
authors.initials: S
authors.lastname: Ohtori
authors.forename: Yasuchika
authors.initials: Y
authors.lastname: Aoki
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Ozawa
authors.forename: Hideo
authors.initials: H
authors.lastname: Doya
authors.forename: Tomoko
authors.initials: T
authors.lastname: Saito
authors.forename: Hideshige
authors.initials: H
authors.lastname: Moriya
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Takahashi
mesh_terms: D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism; D002452:Cell Count; D005456:Fluorescent Dyes; D005727:Ganglia, Spinal / Q000166:cytology* / Q000502:physiology; D006023:Glycoproteins / Q000378:metabolism; D007596:Joints / Q000294:innervation*; D008159:Lumbar Vertebrae / Q000294:innervation*; D008297:Male; D016900:Neurofilament Proteins / Q000378:metabolism; D009475:Neurons, Afferent / Q000166:cytology* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D018048:Receptors, Purinergic P2 / Q000378:metabolism; D058477:Receptors, Purinergic P2X3; D013266:Stilbamidines; D013564:Sympathetic Nervous System / Q000166:cytology / Q000502:physiology
chemical_list: C049774:2-hydroxy-4,4'-diamidinostilbene, methanesulfonate salt; D005456:Fluorescent Dyes; D006023:Glycoproteins; D016900:Neurofilament Proteins; C546409:P2rx3 protein, mouse; C546410:P2rx3 protein, rat; D018048:Receptors, Purinergic P2; D058477:Receptors, Purinergic P2X3; D013266:Stilbamidines; C473590:isolectin B4-binding glycoprotein, mouse; C051774:neurofilament protein H; D015740:Calcitonin Gene-Related Peptide