1995 Fiscal Year Final Research Report Summary
Basic morphological studies on the tooth pain transmission.
| Project/Area Number |
06671814
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Morphological basic dentistry
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| Research Institution | Tokushima University |
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Principal Investigator |
HIURA Akio Tokushima University, School of Dentistry, Associate Professor, 歯学部, 助教授 (00106353)
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| Co-Investigator(Kenkyū-buntansha) |
ISHIZUKA Hiroshi Tokushima University, School of Dentistry, Professor, 歯学部, 教授 (50057494)
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| Project Period (FY) |
1994 – 1995
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| Keywords | Incisor pulp / Trigeminal ganglion / WGA-HRP / Unmyelinated fiber / Capsaicin / NADPH-diaphorase / Plexus of Raschkow |
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| Research Abstract |
We traced the trigeminal sensory neurons with HRP injected into the pulp of mouse lower incisors. Two adult ICR mice were anesthetized with Nembutal. The lower incisor on one side was then cut with a dental disk in the region of tooth eruption from the mandible. Ten microliter of 5% WGA-HRP dissolved in saline was injected into the pulp cavity by microsyringe. The animals were reanesthetized 48 hours later and perfused through the left cardiac ventricle first with saline and then with 200ml of 1% glutaraldehyde-0.5% paraformaldehyde in phosphate buffer(pH7.4). The ipsilateral trigeminal ganglion and brain stem were dissected out, re-fixed in the same fixative for 2 hours at 4ﾟC,and stored in buffered 10% sucrose solution at 4ﾟC.Frozen sections were cut at 30 mum with a Cryostat and rinsed in a solution of 3,3', 5,5'-tetramethylbenzidine and 0.3% H_2O_2. Large diameter of trigeminal ganglion neurons (total : 917 cells) from two animals were measured with ocular micrometer. The size of the mouse trigeminal ganglion neurons varied from 7 to 40 mum in diameter, having a peak between 20 and 25 mum. The HRP-labelled neurons were large, being 20-35mum in diameter. No HRP-incorporated neurons were seen in the brain stem, especially in the mesencephalic nucleus. These results directly or indirectly indicate that larger sensory neurons may give rise to unmyelinated fibers.
Recently, since NO is thought of as a sensory neurotransmitter, we studied the distribution of the ANDPH-diaphorase (NADPH-d, NO synthetic enzyme) in the pulps of lower incisor and molar of the rat. As a result, many NADPH-d positive nerve fibers were seen in the plexus of Rushkow and dentinal tubules, running through the odontoblastic layr. Thus, the results suggest that the pain perception in the dentin and pulp is closlely related to NO-positive nerve fibers.
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