title: Morphological and functional changes in regenerated primary afferent fibres following mental and inferior alveolar nerve transection.
abstract: BACKGROUND
  It is important to know the mechanisms underlying pain abnormalities associated with inferior alveolar nerve (IAN) regeneration in order to develop the appropriate treatment for orofacial neuropathic pain patients. However, peripheral mechanisms underlying orofacial pain abnormalities following IAN regeneration are not fully understood.
  
  
  METHODS
  Head withdrawal threshold (HWT), jaw opening reflex (JOR) thresholds, single-fibre recordings of the regenerated mental nerve (MN) fibres, calcitonin gene-related peptide (CGRP), isolectin B4 (IB4), peripherin, neurofilament-200 (NF-200) and transient receptor potential vanilloid 1 (TRPV1) expression in trigeminal ganglion (TG) cells, and electron microscopic (EM) observations of the regenerated MN fibres were studied in MN- and IAN-transected (M-IANX) rats.
  
  
  RESULTS
  HWT to mechanical or heat stimulation of the mental skin was significantly lower in M-IANX rats compared with sham rats. Mean conduction velocity of action potentials recorded from MN fibres (n = 124) was significantly slower in M-IANX rats compared with sham rats. The percentage of Fluoro-Gold (FG)-labelled CGRP-, peripherin- or TRPV1-immunoreactive (IR) cells was significantly larger in M-IANX rats compared with that of sham rats, whereas that of FG-labelled IB4- and NF-200-IR cells was significantly smaller in M-IANX rats compared with sham rats. Large-sized myelinated nerve fibres were rarely observed in M-IANX rats, whereas large-sized unmyelinated nerve fibres were frequently observed and were aggregated in the bundles at the distal portion of regenerated axons.
  
  
  CONCLUSIONS
  These findings suggest that the demyelination of MN fibres following regeneration may be involved in peripheral sensitization, resulting in the orofacial neuropathic pain associated with trigeminal nerve injury.
authors.affiliation: Department of Physiology, Nihon University School of Dentistry, Tokyo, Japan.|Division of Functional Morphology, Dental Research Center, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Tsuboi
authors.affiliation: Department of Physiology, Nihon University School of Dentistry, Tokyo, Japan.|Department of Oral and Maxillofacial Surgery, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Honda
authors.affiliation: Department of Oral Anatomy, School of Dentistry, Kyungpook National University, Daegu, Korea.
authors.forename: Y C
authors.initials: YC
authors.lastname: Bae
authors.affiliation: Department of Physiology, Nihon University School of Dentistry, Tokyo, Japan.|Division of Functional Morphology, Dental Research Center, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Shinoda
authors.affiliation: Department of Physiology, Nihon University School of Dentistry, Tokyo, Japan.|Division of Functional Morphology, Dental Research Center, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Kondo
authors.affiliation: Department of Physiology, Nihon University School of Dentistry, Tokyo, Japan.|Division of Functional Morphology, Dental Research Center, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Katagiri
authors.affiliation: Department of Physiology, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Echizenya
authors.affiliation: Department of Physiology, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Kamakura
authors.affiliation: Department of Prosthodontics, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: J
authors.initials: J
authors.lastname: Lee
authors.affiliation: Department of Physiology, Nihon University School of Dentistry, Tokyo, Japan.|Division of Functional Morphology, Dental Research Center, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Iwata
mesh_terms: D000344:Afferent Pathways / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D000818:Animals; D004195:Disease Models, Animal; D005157:Facial Pain / Q000209:etiology / Q000378:metabolism / Q000503:physiopathology; D008297:Male; D008340:Mandibular Nerve / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D009412:Nerve Fibers / Q000378:metabolism / Q000502:physiology; D009416:Nerve Regeneration / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D061221:Trigeminal Nerve Injuries / Q000150:complications / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology