CHANGES OF EXPRESSION OF CALCITONIN GENE -RELATED PEPTIDE IN THE RAT TRIGEMINAL MOTOR NUCLEUS AFTER MANDIBULAR NERVE TRANSECTION / 神经解剖学杂志

The purpose of this study was to investigate the changes of calcitonin gene-related peptide (CGRP) expression in the trigeminal motor nucleus (Vmo) following mandibular nerve transection. The expression of CGRP and glial fibrillary acidic protein (GFAP) were detected at 3, 7, 14, 21, 28, 35 and 42 days post-axotomy (dpa) by using immunohistochemical and double-immunofluorescence histochemical methods. And the number of CGRP-positive surviving motoneurons was examined by using image analysis system. The present results showed that there was a "biphasic" up-regulation of CGRP-immunoreactivity at 3 and 35 dpa on the ipsilateral side of the Vmo, and significant changes were also observed on the contralateral side. Quantitative analysis revealed that there was almost no loss of motoneurons in the Vmo but there was an evident increase in GFAP expression around the Vmo neurons on the ipsilateral side after axotomy. The present results suggest that the up-regulation of CGRP may exert its trophic effects in both the acute stress reaction and the recovery of the injured motoneurons, and the activated astrocytes may be well involved in this process.

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 Analysis of GABA and/or Glycine Like Immunoreactive Synaptic Terminals on Masseter gamma-motoneurons for Jaw Closing Muscle of the Rat / 대한해부학회지

The distribution of GABA and/or glycine like immunoreactive nerve terminals on the soma of the masseteric gamma motoneurons were investigated using retrograde tracing of WGA-HRP (wheat germ agglutinin conjugated horseradish peroxidase) and postembedding immunogold labeling methods in serial ultrathin sections. Quantitative analysis of 140 nerve terminals apposing on somata of gamma motoneuron size less than 21 mm in average diameter was performed. The results obtained were as follows. 1. Synaptic covering % of apposing nerve terminals was 21.45+/-11.48% and packing density was 12.85+/-6.17. 2. Nerve terminals immunoreactive (IR) to GABA or glycine were F type containing pleomorphic vesicles with round shape predominant. Majority of nerve terminals immunonegative to GABA or glycine were S type containing spherical vesicles and few of them were F type. 3. 11.42+/-10.00% of examined nerve terminals were IR to GABA only, and 12.71+/-9.85% were IR to GABA and glycine, and 15.21+/-9.58% were IR to glycine only. 4. Synaptic covering % of nerve terminals IR to glycine only was highest (4.58+/-4.50%), followed in order by GABA and glycine (3.18+/-2.77%), and GABA only (2.38+/-2.06%). 5. Among all terminals, immunonegative nerve terminals (60.66+/-14.65%) were much more than nerve terminals immunoreactive to GABA and/or glycine (39.34+/-14.65%) These results show that inhibitory synaptic input and synaptic organization of the masseteric gamma motoneurons reveal characteristic features in contrast to that of alpha motoneurons and which may correlated to the electrophysi-ological characteristics of masseteric gamma motoneurons.

Synaptic connectivity and ultrastructrue of the masseteric muscle spindle afferent trigeminals according to geometric location in the trigeminal motor nucleus of the cat / 대한해부학회지

The purpose of this study was to investigate any relationship between the geometric factors of synaptic contacts of muscle spindle afferent terminals and masseteric motor neurons in the trigeminal motor nucleus. Terminals from the masseteric muscle spindle afferents were stained with intra-axonal injection of HRP and were examined electronmi-croscopically with serial sections at the central and peripheral regions of trigeminal motor nucleus of the cat. The number of terminals examined were 76 in peripheral and 105 in central region. The results obtained were as follows. 1. Most of the labeled terminals showed simple synaptic connectivity. Each terminals in peripheral and central region made synaptic contact with 1 to 5 neuronal profiles. Two or three labeled terminals were occasionally seen to make synaptic contact with the same dendrite. 2. The average number of postsynaptic proximal dendrite per labeled terminal was higher in the central region than in the peripheral region. In contrast, that of postsynaptic distal dendrite per labeled terminal was higher in the peripheral region than in the central region. 3. The average diameter of postsynaptic dendrites in the central region was larger than that in the peripheral region. This imply terminals in the peripheral region contacted with further distal part of the distal dendrite than that in the central region. These results indicate that synaptic connectivity associated with the spindle afferents from masseteric muscle is different according to their geometric location within the trigeminal motor nucleus and suggest that there will be precise interrelationship between the morphology, pattern of synaptic connectivity and functions of muscle spindle afferents.