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.

Re-examination of the topographical distribution of motoneurons innervating the digastric muscle in the rabbit and guinea pig.

The topographical distribution of motoneurons innervating the digastric muscle in the rabbit and guinea pig was re-examined by the retrograde tracing method of HRP (horseradish peroxidase). Motoneurons innervating the anterior belly of the digastric muscle of the rabbit and guinea pig constituted a longitudinal cell column in the ventromedial part of the motor nucleus of the trigeminal nerve. Motoneurons innervating the posterior belly of the digastric muscle were localized in the accessory facial nucleus. No motoneurons supplying the digastric muscle were found within the main facial nucleus.

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.

Localization of motoneurons innervating the stylohyoid muscle in the monkey, cat, rabbit, rat and shrew.

The distribution of motoneurons innervating the stylohyoid muscle was examined in the Japanese monkey (Macaca juscata), cat, rabbit, rat and house musk shrew (Suncus murinus) using the retrograde tracing method of horseradish peroxidase. The enzyme was injected into the stylohyoid muscle after ligating the central cut ends of the main peripheral branches of the facial nerve supplying the superficial facial muscles, or the trunk of the glossopharyngeal nerve supplying the pharyngeal muscles. In the monkey, cat and rabbit, stylohyoid motoneurons were identified in the reticular formation dorsomedial, dorsal or rostrodorsal to the main facial nucleus, and in the dorsomedial or dorsal border region, central part and ventral border region of the main facial nucleus. On the other hand, in the rat and shrew, stylohyoid motoneurons were found in the reticular formation dorsal or dorsomedial to the main facial nucleus and in the dorsal or dorsomedial border region of the main facial nucleus, but not in the central part and ventral border region of the main facial nucleus.

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.

Somatotopic organization of facial nucleus of rabbit. With particular reference to intranuclear representation of perioral branches of the facial nerve.

Somatotopic organization of the facial nucleus was examined in the rabbit by the retrograde HRP (horseradish peroxidase) method; HRP was applied to the peripheral branches of the facial nerve. The facial nucleus is cytoarchitectonically divided into 5 division: the ventromedial, medial, dorsal, lateral and intermediate divisions. The ventromedial division contains neurons supplying the cervical branch. The medial division supplies the anterior auricular branch as well as the posterior auricular branch. The dorsal division is small and contains motoneurons innervating the periorbital regions through the zygomatico-orbital branchlets as well as the anterior auricular branch. Motoneurons innervating the perioral regions are numerous and distributed in the lateral and intermediate division; each of the lateral and intermediate divisions supplies both superior labial and inferior labial branches.

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

The 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 medial) 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. Hypoglossus 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.

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 cerebellar neurons projecting directly to the spinal cord: an HRP study in the Japanese monkey and the cat.

Distribution of cerebellar neurons which send their axons to the spinal cord was examined in 7 Japanese monkeys (Macaca fuscata) and 10 cats by the horseradish peroxidase (HRP) method; retrograde HRP-labeling of cerebellar neurons was observed after HRP injection into the spinal cord. The vast majority of cerebellospinal neurons were located in the fastigial nucleus (FN), posterior interpositus nucleus (PIN), and intermediate medullary region (IMR) between the FN and PIN. These neurons were suggested to send fibers to the cervical and upper thoracic cord segments in the monkey, or to the cervical cord segments in the cat. A few cerebellospinal neurons were also found in the anterior interpositus nucleus (AIN) and the dentate nucleus (DN).

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

Correlation 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.

The structure of the nucleus of the lateral olfactory tract.

The nucleus of the lateral olfactory tract (NLOT) was studied in rats with the rapid Golgi method. The nucleus is in the rostral part of the amygdala and has three distinct layers. Layer I is a superficial, fibrous layer; layer II, an intermediate, cell-dense layer; and layer III, a loosely textured cell and fiber layer. The commissural component of the stria terminalis forms at the apex of layer III. Layer II contains pyramidal and stellate cells; the former is more abundant. The apical dendrites of the pyramidal cells bow outward, point ventrally, and extend through layer I to the pial surface. The apical and basilar dendrites weave a dendrite capsule around layer II, except along its border with layer I. Most pyramidal cell axons go dorsally through layer III into the commissural component of the stria terminalis. The axons normally give off long, thin collaterals that travel rostrally into the forebrain. Other, shorter collaterals remain near the parent cell. Stellate cells have spine-poor dendrites that radiate throughout layers I and II. Their axons generate a dense terminal field that is confined to layer II. A special group of neurons, the border neurons, occur along the junction between layers I and II. Many of them look like modified pyramidal cells, and some look like horizontal cells. The axons of the latter ramify among the pyramidal cell apical bouquet dendrites in layer I. Along the perimeter of layer I, near the pial surface, are rounded cell bodies that have moderately spiny dendrites and axons that project dorsally. Layer III neurons are the largest cells in the NLOT. Three types of large cells were identified: large spiny neurons, large nonspiny neurons, and pyramidal cells, which were least common. The dendrites of all three neuron types reach beyond layer III into layer II or the adjacent anterior amygdala. Their axons were not followed far. They travel dorsally and give off a few collaterals, some of which enter layer II. Also in layer III, mainly in its apical region, are small nonspiny cells. Their dendrites and axons appear to be limited to layer III. The afferent fibers in layer I generally run parallel to the pial surface. They have a few short collaterals and boutons en passant. One afferent group in layer I is made up of thick axons that enter via the rostral edge of the layer.(ABSTRACT TRUNCATED AT 400 WORDS)

The zona incerta: another source of centrifugal fibers to the main olfactory bulb.

Neurons in the ipsilateral anteropolar division of the zona incerta were retrogradely labeled following injections of horseradish peroxidase in the main olfactory bulb. In addition, labeled cell bodies were found in the dorsal hypothalamus. Fewer and less densely labeled neuron cell bodies were seen in the contralateral zona incerta and dorsal hypothalamus. Most of the cells had a characteristic fusiform shaped soma, but a small number of the hypothalamic cells had spherical or conical shaped cell bodies.

Identification of motoneurons supplying the tensor veli palatini muscle in the guinea pig and cat: an horseradish peroxidase study.

Identification of motoneurons supplying the tensor veli palatini muscle was attempted by the horseradish peroxidase (HRP) method in the guinea pig and cat. After HRP injection into the tensor veli palatini muscle, HRP-labeled neurons were seen in the regions closely medial to the cluster of the lateral pterygoid motoneurons in the dorsolateral division of the trigeminal motor nucleus. In the guinea pig the tensor veli palatini motoneurons were observed at the level of the whole rostrocaudal extent of the trigeminal motor nucleus, while in the cat they were seen at the level of the rostral two-thirds of the nucleus.

Localization of motoneurons innervating the tensor tympani muscles: an horseradish peroxidase study in the guinea pig and cat.

Motoneurons innervating the tensor tympani muscle were identified in the adult guinea pig and cat by the horseradish peroxidase (HRP) method. After HRP injection into the tensor tympani muscle, HRP-labeled neurons were seen in the regions outside the cytoarchitectonically-defined confines of the trigeminal motor nucleus; in the regions rostral to the rostral pole of the nucleus, as well as in the regions ventral and ventrolateral to the nucleus at the levels of the rostral half (guinea pig) or the rostral two-thirds (cat) of the nucleus. The tensor tympani motoneurons were generally smaller than the masticatory motoneurons.

A retino-pulvinar projection in the macaque monkey as visualized by the use of anterograde transport of horseradish peroxidase.

A direct retino-pulvinar connection was found in the Japanese monkey (Macaca fuscata) by the anterograde horseradish peroxidase (HRP) method. HRP injected into the vitreous cavity of one eye labeled a few small clusters of optic fiber terminals in the medial border regions of the inferior pulvinar nucleus bilaterally, with a contralateral predominance.

Localization of masticatory motoneurons in the trigeminal motor nucleus of the guinea pig.

The myotopical arrangement of masticatory motoneurons was examined in the guinea pig by the horseradish peroxidase method. The trigeminal motor nucleus was composed of dorsolateral and ventromedial divisions; the former was seen in the whole rostrocaudal extent of the nucleus, while the latter was present at levels of the caudal two thirds of the nucleus. The jaw-closer motoneurons were located in the dorsolateral division, and the jaw-opener motoneurons (mylohyoid and anterior digastric motoneurons) were seen in the ventromedial division.

Direct projections from the extrathalamic forebrain structures to the neocortex in the macaque monkey.

Extrathalamic direct projections from the subcortical forebrain structures to the neocortex were examined in the macaque monkey by the horseradish peroxidase method. The enzyme, when injected into discrete regions in the neocortex, labeled cell bodies of extrathalamic forebrain neurons in the basal nucleus of Meynert, nucleus of the diagonal band, medial septal nucleus, hypothalamus, claustrum and dorsolateral part of the basal amygdaloid nucleus. Neurons in the basal nucleus of Meynert, lateral hypothalamus and claustrum appeared to send their axons widely, but not diffusely, to the neocortex.

Extrageniculate projections to the visual cortex in the macaque monkey: an HRP study.

Extrageniculate projections to the visual cortex were examined in the macaque monkeys by the horseradish peroxidase (HRP) method. Extrageniculate neurons sending fibers to the visual cortex were found in the lateral and inferior pulvinar nuclei, paracentral thalamic nucleus, claustrum, basal nucleus of Meynert, lateral part of the basal amygdaloid nucleus, lateral hypothalamus, locus coeruleus, and dorsomedial and midline regions of the pontine tegmentum.

Topographical representation of the hypoglossal nerve branches and tongue muscles in the hypoglossal nucleus of macaque monkeys.

Representation of the hypoglossal nerve branches and tongue muscles was examined in the hypoglossal nucleus of macaques by the horseradish peroxidase method. The nucleus was divided cytoarchitectonically into the medial and lateral divisions at rostral levels, and into the mediodorsal, medioventral, ventral and laterodorsal divisions at caudal levels. The medial, mediodorsal, medioventral and ventral divisions supplied the medial branch. The lateral and laterodorsal divisions supplied the lateral branch. The geniohyoid motoneurons (MN) composed the ventral division. The genioglossus MN were clustered dorsally in the medial division. The hyoglossus and styloglossus MN were located most laterally in the laterodorsal division.