서순응형 치근막 일차구심성 신경섬유 종말부의 Subnucleus oralis에서의 시냅스 양상에 관한 전자현미경적 연구

ELECTRON MICROSCOPIC STUDY OF SLOWLY ADAPTING PERIODONTAL MECHANORECEPTIVE PRIMARY AFFERENT FIBERS WITHIN THE SUBNUCLEUS ORALIS OF THE CAT

단일축삭내 HRP 주입기법에 의해 서순응형 치근막 기계적자극수용기에서 오는 일차구심성 신경섬유증 무수축삭에 의해 연결되어 있는 종말지의 시냅양상 및 미세구조에 대한 연구결과는 다음과 같았다. 1. 표식된 stem collateral은 첫 bouton을 형성할 때까지는 수질을 함유하고 있었으며, 그 직경은 약 $0.81-1.38{\mu}m$이었고, 각 terminal bouton은 특징적으로 모두가 무수축삭에 의해 연결되어 있었다. 2. 대부분의 표식 bouton은 dome형태를 나타내었으며, 때때로 길쭉한 모양 혹은 둥근모양의 bouton도 다소 관찰되었으나 scalloped 형태 혹은 glomerulus 형태의 bouton은 전혀 나타나지 않았으며 각 표식 bouton은 균일한 형태 및 크기(직경 $47.60{\pm}3.58{\mu}m$)를 가진 밝은 타원 및 원형의 소포들을 함유하고 있었다. 3. 표식 bouton은 평균직경 $1.15{\pm}0.24{\mu}m$로서 비교적 작았고 평균 $1.11{\pm}0.31$개의 다른 neuronal propile과 시냅스를 이루었는데 그중 단 1개의 neuronal propile과 시냅스를 이루는 것이 89.4%, 2개의 neuronal propile과 시냅스를 이루는 것이 10.6%로서 대단히 단순한 형태의 시냅스를 이루는 것이 특징적으로 나타났으며, 그중 대부분(80.03%)이 dendritic shaft 혹은 spine과만 시냅스를 이루었으며 p-ending과 시냅스를 이루는 것은 6.1%였고 synaptic triad는 전혀 관찰되지 않았다.

It was revealed that the morphology and projection pattern of terminal arbors from single primary afferent are different among distinct fiber types, functional types and the different subdivision of trigeminal sensory nucleus complex(TSNC). But it was not identified the ultrastructural morphology and synaptic connections of terminal arbors from each primary afferent within TSNC. So we employed the intra-axonal horseradish peroxidase(HRP) injection technique to define the terminal arbors of primary afferent fiber from slowly adapting mechanoreceptors in the periodontal ligament of the cat, and examined 66 labeled terminal arbors within the rostrodorsomedial part(Vo.r) of the trigeminal nucleus oralis, electromicroscopically with 90nm serial sections. All the boutons labelled with HRP contained clear, spherical and uniform sized synaptic vesicles(diameter : $47.66{\pm}3.58nm$ ). Most of the labelled boutons were boutons en passant type and they were connected by unmyelinated axonal strand. In which neurofilament and microtubule was not developed but occasionally contained synaptic vesicle in contrast to the myelinated axon. The size of the labelled bouton was relatively small(long diameter : $1.46{\pm}0.24{\mu}m$, short diameter $0.85{\pm}0.26{\mu}m$, average diameter $1.15{\pm}0.24{\mu}m$) and the shape of which varied from dome to elongated shape, but scalloped glomerulus shape was not developed. Each primary ending in Vo.r made synapse with one or two neuronal propiles(average : $1.11{\pm}0.31$), of which, 89.4% of labelled boutons made synapse with only one neuronal pro pile, the remainder, 10.6% of labelled boutons, made synapse with two neuronal propile. So characteristically they made very simple synapse. Most of labelled boutons(80.03%) made asymmetrical synapse only with dendritic shaft or spine, and 6.1% of labelled boutons received symmetrical synapse from pleomorphic vesicle containing axonal ending(p-ending). So presynaptic inhibiton was relatively scarce. Synaptic triad, in which a p-ending is presynaptic both pre-and post-synaptic element of the axo-dendritic contact from the labelled primary ending was not observed.