Processing Mechanism of Sensory Information Originated from the Oral Cavity in the Trigeminal Nucleus Oralis / 대한해부학회지

To analyze the synaptic characteristics of axon terminals originated from the tooth pulp in the trigeminal nucleus oralis, labeling of tooth pulp afferents with wheat-germ agglutinin conjugated horseradish peroxidase and morphometric analysis with electron microscopic photographs were performed. The results obtained from 23 labeled endings were as follows. All of the labeled boutons contained clear and round synaptic vesicles (dia. 45~55 nm). 3 (13.64%) out of 23 labeled endings have 20~105 dense cored vesicles and do not make synaptic contacts with p-endings. But remaining 20 labeled endings (86.36%) almost do not have dense cored vesicles and 12 of them make synaptic contacts with p-endings. The mean number of synaptic contacts was 2.61+/-2.06 and the postsynaptic profiles were usually middle or distal dendrite and dendritic spine (1.74+/-1.36) rather than soma or proximal dendrite. The mean number of synaptic contacts with pendings was 0.87+/-1.01. And the frequency of the synaptic triads were 0.39+/-0.58. The vesicle density was 993.23+/-267.41/mum(2). The volume of labeled bouton was 3.54+/-2.20 mum(3) and highly correlated (P < 0.01) with surface area (11.78+/-4.92 mum(2), r = 0.95), total apposed surface area (2.90+/-1.56 mum(2), r=0.72), total active zone area (0.61+/-0.37 mum(2), r = 0.82), mitochondrial volume (0.75+/-0.53 mum(3), r = 0.94), the number of synaptic vesicles (2621.30+/-1473.61, r= 0.91) and the number of synaptic contacts (r = 0.76). These results suggest that there are two groups of tooth pulp afferent terminals according to the presence of dense cored vesicles in the trigeminal nucleus oralis. And the sensory processing mechanism of each groups may be different. And the "size principle" of Pierce & Mendell (1993) is also applicable to these terminals.

Quantitative Ultrastructural Analysis of Periodontal Afferent Terminals in the Trigeminal Motor Nucleus / 대한해부학회지

Little is known about processing mechanism of sensory input from the periodontal ligaments to the trigeminal motor nucleus for the control of chewing force and modulation of chewing pattern. Low threshold mechanoreceptive periodontal afferent was labeled with horseradish peroxidase by use of intra-axonal injection technique and investigated with electron microscopy. Quantitative ultrastructural analysis was performed on the 39 serially reconstructed labeled boutons in the trigeminal motor nucleus in cat. Labeled bouton contained clear spherical vesicles and one or two large dense cored vesicles. Most of labeled boutons were dome or round shape. All the analysed labeled boutons were presynaptic to dendritic shaft or distal dendrite and those presynaptic to soma or proximal dendrite were not observed. A large number of labeled boutons (46.2%) were postsynaptic to one or two presynaptic pleomorphic vesicle containing endings. Synaptic triad, in that a presynaptic ending which is presynaptic to the labeled bouton, in turn, is presynaptic to dendrite that is postsynaptic to the labeled bouton, was observed in 10.3% of the labeled boutons. Most of the labeled boutons showed simple synaptic organization, in that 64.1% of the labeled boutons made synaptic contacts with one or two neuronal profiles. One (2.6%) of the 39 analyzed labeled boutons showed synaptic contacts with 5 or more neuronal profiles. Labeled bouton volume, mitochondrial volume, apposed surface area and active zone area showed wide variation. These ultrastructural parameters were positively correlated with bouton volume. The values for apposed surface area and active zone area with presynaptic p-endings, in contrast to those with postsynaptic dendrites, showed narrow range and had little correlation with bouton volume. The present study revealed characteristic features on ultrastructural parameters of labeled boutons from periodontal afferent which is involved in periodontal masseteric reflex, and that influence on the postsynaptic trigeminal motoneurons showed wide variability.

Quantitative and Ultrastructural Analysis of Afferent Terminals from Tooth Pulp in the Trigeminal Principal Sensory Nucleus / 대한해부학회지

To analyze the synaptic characteristics of axon terminals originated from tooth pulp in the trigeminal principal sensory nucleus, and find morphological evidence that p-endings on these terminals use GABA as neurotransmitter, labeling of tooth pulp afferents with wheat -germ agglutinin conjugated horseradish peroxidase, postembedding immunocytochemistry and morphometric analysis were performed. The results obtained were as follows. The labeled boutons contained clear and round synaptic vesicles, and the mean number of synaptic contacts was 4.21 +/- 2.58. The postsynaptic profiles were usually middle or distal dendrites and dendritic spines rather than soma or proximal dendrites. The mean number of synaptic contacts with p -endings was 2.62 +/- 2.01. The volume of labeled bouton was 4.39 +/- 3.08 micro meter 3 and highly correlated (P<.01) with surface area (r = 0.96), total apposed surface area (r = 0.84), total active zone area (r = 0.84), mitochondrial volume (r = 0.95), the number of synaptic vesicles (r = 0.92), the number of synaptic profiles (r = 0.76) and the number of synaptic p -endings (r = 0.67). The p -endings contained pleomorphic synaptic vesicles. The volume of p -ending was 0.91 +/- 0.47 micro meter 3 and highly correlated (P<.01) with surface area (r = 0.94), total apposed surface area (r = 0.76), total active zone area (r = 0.62), mitochondrial volume (r = 0.70) and the number of synaptic vesicles (r = 0.94). P -endings were GABA immunoreactive. These results suggest that tooth pulp afferent terminals in trigeminal principal sensory nucleus may be related to complex processing of sensory information and presynaptic p -endings using GABA as neurotransmitter, are important in this sensory processing. The "size principle" of Pierce and Mendel (1993) is also applicable to tooth pulp afferent terminals and presynaptic p -endings.