Calretinin-like immunoreactivity in the Ruffini endings, slowly adapting mechanoreceptors, of the periodontal ligament of the rat incisor.
The distribution and ultrastructural localization of calretinin (CR)-like immunoreactivity (-LI) were investigated in the lingual periodontal ligament of rat incisors. Some thick nerve fibers within the nerve bundle displayed CR-LI; these CR-like immunoreactive (-IR) nerve fibers entered the alveolar half of the lingual periodontal ligament of the incisor where dendritic terminal arborization was exhibited. Thin and beaded CR-IR nerve fibers were rarely observed in the periodontal ligament. Observations of adjacent sections immunostained with protein gene-product 9.5 (PGP 9.5) revealed that most, if not all, PGP 9.5-IR nerve terminals showing a dendritic arborization expressed CR-LI. Immunoelectron microscopic observations showed that electron-opaque immunoreaction products were localized in the axoplasm of the axon terminals, except for the mitochondria, which were surrounded by Schwann sheaths and multiple-layered basal lamina. Neither cell bodies, the cytoplasmic extension of terminal Schwann cells, nor other cellular elements such as periodontal fibroblasts exhibited CR-LI. The present findings suggest that Ruffini endings, an essential mechanoreceptor in the periodontal ligament and categorized as a slowly adapting mechanoreceptor, express CR-LI, and that CR may participate in the Ca2+ homeostasis against external stimuli in the periodontal Ruffini endings.
Ochi
K
K
Department of Oral Anatomy, Niigata University School of Dentistry, Japan. ochi@dent.niigata-u.ac.jp
Wakisaka
S
S
Youn
S H
SH
Hanada
K
K
Maeda
T
T
D000818:Animals; D064032:Calbindin 2; D007180:Incisor / Q000502:physiology*; D008297:Male; D008465:Mechanoreceptors / Q000378:metabolism* / Q000648:ultrastructure; D016253:Microscopy, Immunoelectron; D010513:Periodontal Ligament / Q000294:innervation*; D051381:Rats; D017207:Rats, Sprague-Dawley; D064030:S100 Calcium Binding Protein G / Q000378:metabolism*
C576512:Calb2 protein, rat; D064032:Calbindin 2; D064030:S100 Calcium Binding Protein G