Masanori Uemura-Sumi

The distribution of hypoglossal motoneurons in the dog, rabbit and rat.

SummaryThe distribution of motoneurons innervating the extrinsic tongue muscles was studied in the dog, rabbit and rat using the horseradish peroxidase technique. In these mammals, hypoglossal motoneurons were clustered in roughly ventral (or media) and dorsal (or lateral) groups. Axons of hypoglossal motoneurons in the ventral (or medial) group passed via the medial branch of the hypoglossal nerve, and those in the dorsal (or lateral) group by way of the lateral branch of the hypoglossal nerve. Motoneurons supplying the geniohyoid or genioglossus muscle were distributed, respectively, in the ventral or lateral aspect of the ventral (or medial) cluster of hypoglossal motoneurons. Hyoglossus and styloglossus motoneurons were located in the lateral aspect of the dorsal (or lateral) cluster. The area of distribution of hypoglossus motoneurons overlapped with that of styloglossus motoneurons. It seems likely that motoneurons innervating intrinsic tongue muscles form the remainder of the hypoglossal nucleus. The largest motoneurons in the hypoglossal nucleus were distributed in the cluster of geniohyoid motoneurons. Thus, in the present study a somatotopic arrangement of motoneurons innervating the extrinsic tongue muscles was found, in keeping with previous studies using the retrograde cell degeneration technique.

Amygdaloid pathway to the trigeminal motor nucleus via the pontine reticular formation in the rat

The connections of the amygdala with the trigeminal motor nucleus were studied by light and electron microscopy. Horseradish peroxidase (HRP) experiments showed that the pontine reticular formation, ventromedial to the spinal trigeminal nucleus at the level rostral to the genu of the facial nerve, receives fibers from the central nucleus of the amygdala ipsilaterally and sends fibers to the trigeminal motor nucleus contralaterally. Electron microscopic observations were carried out on the pontine reticular formation after electrolytic lesions in the central nucleus of the amygdala and HRP injections into the contralateral trigeminal motor nucleus were made on the same animal. These experiments using the combined degeneration and HRP technique clearly demonstrated that degenerating amygdaloid fibers made synaptic contacts with retrogradely labeled neurons.

Representation of the main branches of the facial nerve within the facial nucleus of the Japanese monkey (Macaca fuscata).

The facial nucleus of the Japanese monkey was divided cytoarchitectonically into the ventral, medial, intermediate, dorsal and lateral divisions. When horseradish peroxidase (HRP) was applied to the inferior labial, cervical or posterior auricular branch of the facial nerve, HRP-labeled neurons were seen in the lateral, ventral or medial division of the facial nucleus, respectively. After applying HRP to the anterior auricular-zygomatico-orbital branch, labeled neurons were observed mainly in the intermediate and dorsal divisions. HRP applied to the superior labial branch labeled neurons within the dorsal and lateral divisions.

Distribution of axons showing calcitonin gene-related peptide- and/or substance P-like immunoreactivity in the sensory trigeminal nuclei of the cat.

Distribution of axons with calcitonin gene-related peptide (CGRP)-like and/or substance P (SP)-like immunoreactivity (LI) within the sensory trigeminal nuclei was examined in the cat before and after trigeminal rhizotomy. Axons with CGRP-LI or SP-LI were seen throughout the principal sensory trigeminal nucleus (Vp) and spinal trigeminal nuclei, including the medullary dorsal horn (MDH). They were densely distributed particularly in the dorsolateral part of the dorsal subnucleus of the Vp, ventromedial marginal zone of the ventral subnucleus of the Vp, dorsomedial and ventromedial parts of the oral spinal trigeminal nucleus, ventromedial and lateral marginal zones of the interpolar spinal trigeminal nucleus, and lamina I, outer part of lamina II and lamina V of the MDH. Most of the CGRP-LI axons exhibited SP-LI, while many SP-LI axons did not show CGRP-LI. After trigeminal rhizotomy, almost all CGRP-LI axons disappeared from the ipsilateral sensory trigeminal nuclei, while a considerable number of SP-LI axons remained intact throughout the nuclei; these SP-LI axons did not show CGRP-LI. The results indicate that CGRP-LI axons within the sensory trigeminal nuclei exhibit SP-LI and are of peripheral origin, and that SP-LI axons without CGRP-LI are of central origin.

Correlation of the main peripheral branches of the facial nerve with the cytoarchitectonic subdivisions of the facial nucleus in the guinea pig

SummaryCorrelation of the main peripheral branches of the facial nerve with morphological subdivisions of the facial nucleus was examined in the guinea pig by the retrograde horseradish peroxidase method. The facial nucleus of the guinea pig was divided cytoarchitectonically into the dorsolateral, lateral, intermediate, medio-intermediate, medial, and ventromedial divisions; the ventromedial division was further divided into the major, dorsal and lateral parts. Six main branches of the facial nerve were identified; the zygomatico-orbital, cervical, posterior auricular, anterior auricular, superior labial, and inferior labial branches. After applying HRP to the main branches of the facial nerve, the pattern of distribution of HRP-labelled neuronal cell bodies within the facial nucleus was examined: the dorsolateral division, dorsal part of the ventromedial division, major part of the ventromedial division, lateral part of the ventromedial division, or medial division contained the cell bodies of respectively the zygomatico-orbital, cervical, posterior auricular, anterior auricular, or superior labial branches, while each of the lateral, intermediate, and medio-intermediate divisions contained the cell bodies of both the superior labial and inferior labial branches.

Representation of the tensor veli palatini muscle in the trigeminal motor nucleus of the Japanese monkey (Macaca fuscata)

Distribution of motoneurons supplying the tensor veli palatini (TVP) muscle was examined in the Japanese monkey (Macaca fuscata) by the retrograde horseradish peroxidase (HRP) method. Neurons labeled with HRP which was injected into the tensor veli palatini muscle were seen in the ventromedial aspects of the dorsolateral division of the trigeminal motor nucleus, at all rostrocaudal levels of the trigeminal motor nucleus. The vast majority of these TVP motoneurons were distributed around the margin, especially the dorsal margin, of the cluster of motoneurons which innervate the lateral pterygoid muscle.