Peripherin- and CGRP-immunoreactive nerve fibers in rat molars have different locations and developmental timing.
Developing rat molars gain mature sensitivity to electric stimulation at 4-5 weeks after eruption, but the related mechanisms are incompletely understood. Preliminary studies showed weak co-localization of calcitonin gene-related peptide (CGRP) immunoreactivity (IR) with peripherin (PER) or neurofilament protein (NF) in rat molar nerve fibers, while the latter two co-localized extensively.


OBJECTIVE
Our goal was to compare timing and location of PER-IR and CGRP-IR innervation in rat first molars during tooth maturation.


METHODS
We used single and double immunocytochemistry to study molars of rats aged 10 days to 1 year. Neural patterns were compared with odontoblast maturation stages, dentinogenesis, formation of cell-free and cell-rich zones, and root closure.


RESULTS
Spatial and temporal patterns showed that most CGRP-IR and PER-IR have different terminal domains in teeth. PER-IR fibers were well established among immature odontoblasts prior to tooth eruption, but CGRP-IR fibers were absent. Two weeks after eruption of first molars, many CGRP-IR beaded fibers entered dentin, the larger PER-IR fibers began shifting away from odontoblasts towards the pulp, and the symmetrical PER-IR pulpal pattern was being established. The CGRP-IR fibers continued to increase their asymmetric dentinal innervation until root growth was completed, during which time odontoblasts matured, the cell-free and cell-rich zones appeared, and roots closed.


CONCLUSIONS
Sensory maturation of rat molars coincides with closed root apices, extensive innervation of dentin by CGRP-IR nerve fibers, and the appearance of the mature avascular odontoblast layer next to cell-free and cell-rich zones in the pulp horns.
Veerayutthwilai
Orapin
O
Oral Biology, University of Washington, Seattle, WA 98195, USA.
Luis
Nadyne A
NA
Crumpton
Rosa M
RM
MacDonald
Glen H
GH
Byers
Margaret R
MR
D000818:Animals; D015415:Biomarkers / Q000032:analysis; D015740:Calcitonin Gene-Related Peptide / Q000032:analysis*; D003804:Dentin / Q000254:growth & development / Q000294:innervation; D003810:Dentinogenesis / Q000502:physiology; D007150:Immunohistochemistry; D007381:Intermediate Filament Proteins / Q000032:analysis*; D008562:Membrane Glycoproteins / Q000032:analysis*; D008963:Molar / Q000254:growth & development* / Q000294:innervation*; D009412:Nerve Fibers / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000032:analysis*; D016900:Neurofilament Proteins / Q000032:analysis; D009804:Odontoblasts / Q000502:physiology; D009805:Odontogenesis / Q000502:physiology; D064531:Peripherins; D051381:Rats; D017207:Rats, Sprague-Dawley; D014078:Tooth Eruption
D015415:Biomarkers; D007381:Intermediate Filament Proteins; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D016900:Neurofilament Proteins; D064531:Peripherins; D015740:Calcitonin Gene-Related Peptide