Immunohistochemical localization of SNARE core proteins in intrapulpal and intradentinal nerve fibers of rat molar teeth.
OBJECTIVE
The present study was designed to elucidate whether three soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptor (SNARE) core proteins, syntaxin-1, synaptosomal-associated protein of 25kDa (SNAP-25), and vesicle-associated membrane protein-2 (VAMP-2), are present in the dental pulp of the rat molar at both the light and electron microscopic levels.


METHODS
Immunohistochemistry for protein gene product 9.5 (PGP 9.5), a pan-neuronal marker, syntaxin-1, SNAP-25, and VAMP-2 was performed on decalcified rat molars for light and electron microscopic analyses. Double-immunolabeling of PGP 9.5 and the SNARE core proteins, as well as combinations of the SNARE core proteins, was also carried out.


RESULTS
PGP 9.5-immunoreactive nerve fibers ran toward the coronal region, ramified at the subodontoblast layer, and formed the subodontoblastic nerve plexus. Most nerve fibers penetrated the predentin and dentin along the dentinal tubules. Most, if not all, nerve fibers displayed immunoreactivity for syntaxin-1, SNAP-25, and VAMP-2. Immunoelectron microscopic analyses confirmed the presence of immunoreactivity for the SNARE core proteins within the intradental axonal elements.


CONCLUSIONS
The present findings suggest that, since SNARE core proteins participate in the docking and exocytosis of synaptic vesicles in the central nervous system, they may contribute to vesicle exocytosis from the dental nerve fibers even though there are no apparent synapses.
Department of Oral Anatomy and Developmental Biology, Osaka University Graduate School of Dentistry, 1-8, Yamadaoka, Suita, Osaka, 565-0871, Japan.
Shiho
S
Honma
Department of Oral Anatomy and Developmental Biology, Osaka University Graduate School of Dentistry, 1-8, Yamadaoka, Suita, Osaka, 565-0871, Japan.
Kohki
K
Kadono
Department of Oral Anatomy and Developmental Biology, Osaka University Graduate School of Dentistry, 1-8, Yamadaoka, Suita, Osaka, 565-0871, Japan.
Akiyo
A
Kawano
Department of Oral Anatomy and Developmental Biology, Osaka University Graduate School of Dentistry, 1-8, Yamadaoka, Suita, Osaka, 565-0871, Japan. Electronic address: wakisaka@dent.osaka-u.ac.jp.
Satoshi
S
Wakisaka
D000818:Animals; D001369:Axons / Q000378:metabolism; D003782:Dental Pulp / Q000000981:diagnostic imaging / Q000294:innervation*; D003786:Dental Pulp Cavity / Q000294:innervation / Q000378:metabolism; D003804:Dentin / Q000033:anatomy & histology / Q000294:innervation / Q000648:ultrastructure; D005089:Exocytosis; D007150:Immunohistochemistry; D008297:Male; D016253:Microscopy, Immunoelectron / Q000379:methods; D008963:Molar / Q000294:innervation* / Q000648:ultrastructure; D009412:Nerve Fibers / Q000378:metabolism* / Q000648:ultrastructure; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009804:Odontoblasts / Q000166:cytology / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D050600:SNARE Proteins / Q000378:metabolism*; D013569:Synapses / Q000737:chemistry / Q000648:ultrastructure; D043222:Ubiquitin Thiolesterase / Q000378:metabolism
D009419:Nerve Tissue Proteins; D050600:SNARE Proteins; C489034:UCHL1 protein, rat; D043222:Ubiquitin Thiolesterase
Exocytosis; Intradentinal nerve; Intrapulpal nerve; SNAP-25; Syntaxin-1; VAMP-2