Quantitative ultrastructural analysis of the neurofilament 200-positive axons in the rat dental pulp.
BACKGROUND
Previous studies have suggested that myelinated axons lose their myelin and become thinner in their peripheral course to the target organ. In this study, we investigated the morphologic changes of pulpal myelinated axons between their root portion (radicular pulp) and their terminal area (peripheral pulp).


METHODS
Sections of pulp of the rat upper molar teeth were immunostained for the marker of myelinated axons neurofilament (NF) 200. The proportion of NF200+ myelinated and unmyelinated fibers and their sizes were analyzed by using quantitative electron microscopy.


RESULTS
The axon area, myelin thickness, and fraction of NF200+ myelinated axons of all NF200+ axons were significantly lower in peripheral than in radicular pulp. In addition, large unmyelinated axons were frequently observed in peripheral pulp.


CONCLUSIONS
These results suggest that pulpal innervation originates predominantly from myelinated axons, and the myelinated axons undergo extensive morphologic changes during their course from the radicular to the peripheral pulp.
Paik
Sang Kyoo
SK
Department of Oral Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, Korea.
Lee
Dae Seop
DS
Kim
Jae Young
JY
Bae
Jin Young
JY
Cho
Yi Sul
YS
Ahn
Dong Kuk
DK
Yoshida
Atsushi
A
Bae
Yong Chul
YC
D000818:Animals; D001369:Axons / Q000378:metabolism / Q000648:ultrastructure*; D003782:Dental Pulp / Q000166:cytology / Q000294:innervation*; D008297:Male; D009186:Myelin Sheath / Q000648:ultrastructure; D009413:Nerve Fibers, Myelinated / Q000648:ultrastructure*; D036421:Nerve Fibers, Unmyelinated / Q000648:ultrastructure; D016900:Neurofilament Proteins / Q000032:analysis*; D051381:Rats; D017207:Rats, Sprague-Dawley
D016900:Neurofilament Proteins; C051774:neurofilament protein H