Increase of CGRP-containing nerve fibers in the rat periodontal ligament after luxation.
The distribution of calcitonin gene-related peptide (CGRP) was examined in the periodontal ligament (PDL) after experimental luxation injury of the rat first molar tooth. The luxational injury increased the number of CGRP-immunoreactive (IR) nerve fibers. At 3-7 days, numerous CGRP-IR nerve fibers appeared throughout the injured PDL. These nerve fibers terminated as free nerve endings within resorption cavities. Immunohistochemistry for receptor activity modifying protein 1 (RAMP1) also demonstrated that the subunit of CGRP receptor was expressed by periodontal cells adjacent to the alveolar bone in the intact and injured PDL. RAMP1-IR cells were divided into two types; small cells with single nucleus and large cells with 2-6 nuclei. After the luxational injury, both types of RAMP1-IR cells abundantly appeared within resorption cavities. As a result, the treatment increased the number of large RAMP1-IR cells at 3-7 days and small RAMP1-IR cells at 7 days. In addition, a double immunofluorescence analysis demonstrated that CGRP-IR nerve fibers were seen away from RAMP1-IR cells in the intact PDL. After the traumatic injury, however, CGRP-IR nerve fibers appeared in the close vicinity of small and large RAMP1-IR cells at 5-7 days. The morphology and distribution of RAMP1-IR cells suggest that they contain osteoblasts and osteoclasts. By affecting osteoclasts and osteoblasts, CGRP may have effects on bone remodeling in the luxated PDL.
Division of Orthodontics and Dentofacial Orthopedics, Tohoku University Graduate School of Dentistry, Sendai, Japan.
Tessei
T
Nagayama
Masahiro
M
Seiryu
Toru
T
Deguchi
Mitsuhiro
M
Kano
Toshihiko
T
Suzuki
Teruko
T
Takano-Yamamoto
Hiroyuki
H
Ichikawa
D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000096:biosynthesis*; D008297:Male; D009412:Nerve Fibers / Q000378:metabolism* / Q000473:pathology; D010513:Periodontal Ligament / Q000166:cytology / Q000378:metabolism* / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D058262:Receptor Activity-Modifying Protein 1 / Q000096:biosynthesis; D014084:Tooth Avulsion / Q000378:metabolism* / Q000473:pathology
C545508:Ramp1 protein, rat; D058262:Receptor Activity-Modifying Protein 1; D015740:Calcitonin Gene-Related Peptide