Matsuo Matsushita

Brainstem projections from the lateral hypothalamic area in the rat, as studied with autoradiography

Descending projections from the lateral hypothalamic area to the brainstem were studied, using [3H]-amino acid autoradiography, in the rat. Two main ipsilateral paths were reorganized. One is the periventricular fiber system projecting to the midbrain central gray. The other is a fiber system which eventually descends the central tegmental field, projecting strongly to the dorsal raphe nucleus, medial and lateral parabrachial nuclei, nucleus reticularis parvocellularis, solitary nuclei and dorsal motor nucleus of the vagus nerve. Sparse projections were observed to the nuclei raphe magnus, obscurus and pallidus, group B3 (or the ventrolateral subpial group) and spinal trigeminal nucleus.

Identification and distribution of the spinal and hypophyseal projection neurons in the paraventricular nucleus of the rat. A light and electron microscopic study with the horseradish peroxidase method.

SummaryThe distribution of labeled neurons in the paraventricular nucleus of the hypothalamus (PVN) was studied following injections of horseradish peroxidase (HRP) into the spinal cord (C8 to T1) or the hypophysis in the rat. Injections were also made in the spinal cord in another group of animals, which were subjected to water deprivation for a period of 3 days, and the PVN of these animals was examined with the electron microscope.Spinal projection neurons (paraventriculospinal tract, PVST, neurons) formed two groups; the dorsal and the ventral groups. They were located within the parvocellular part of the PVN and fused into one at the caudal level. The neurons of the dorsal group were well assembled whereas those of the ventral group were intermingled with paraventriculohypophyseal tract (PVHT) neurons, which were concentrated in the magnocellular part. Electron microscopic observations revealed that HRP-labeled neurons after spinal injections did not contain neurosecretory granules and that they were not affected by water deprivation. On the other hand, neurons containing a number of neurosecretory granules displayed a significant degree of dilatation of the endoplasmic reticulum as the result of water deprivation. These neurons contained no HRP granules.The present findings suggest that the PVST neurons are distinct from the PVHT neurons and that the neuronal groups of both systems form different cell columns within the nucleus.

Cells of origin of the spinocerebellar tract in the rat, studied with the method of retrograde transport of horseradish peroxidase.

Following injections of horseradish peroxidase into the cerebellum, the distribution of labeled neurons was studied in the whole length of the spinal cord of the rat. To find the ascending side of the axons, injections were made following hemisections at C1 or between C1 and C2. Labeled spinocerebellar tract neurons were classified into two groups according to the axonal course in the spinal cord; one is composed of neurons with uncrossed ascending axons and the other, neurons with crossed ascending axons. Neurons of origin of the uncrossed tracts were located in the medial part of lamina VI of C2 to C8, the central part of lamina VII of C4 to C8, lamina V of C7 to L3 and Clarkes column. Neurons of origin of the crossed tracts were found in the central cervical nucleus of C1 to C3, the intermediate zone and the ventral horn of the lower thoracic and the lumbar segments (T11 to L3), and in the dorsal horn, the medial part of lamina VII and the ventrolateral part of the ventral horn of the sacral and caudal spinal cord. In comparison with our previous results in the cat, it was suggested that the spinocerebellar system in the rat is organized in the same fashion as in the cat, in terms of the location and the intraspinal axonal course of the cells of origin.

Olivary projections to the cerebellar nuclei in the cat

SummaryProjections from the inferior olive to the cerebellar nuclei have been studied in the cat using Nautas silver technique. 1. Numerous degenerating terminals occur after lesions in the inferior olivary complex in the medial nuclei of both sides; the degeneration is considerably less in the subnucl. medialis parvicellularis of both sides. In the interpositus nuclei of both sides degenerating terminals are also abundant, especially in their dorsal and lateral parts. In the lateral nucleus a number of degenerating terminals are seen on both sides restricted to dorsal and lateral parts of the nuclei. Degeneration is scanty in the subnucl. lateralis parvicellularis. 2. Projection of the olivocerebellar fibers to the cerebellar nuclei is always bilateral. The fibers originate in the inferior olive and ascend mainly through the contralateral, however, some also through the ipsilateral restiform body. The olivocerebellar fibers that have crossed in the medulla terminate in the medial and the interpositus nuclei of both sides. It is suggested that the degenerating terminals found in the cerebellar nuclei are derived from collaterals of the olivocerebellar tract fibers.

The cells of origin of the trigeminothalamic, trigeminospinal and trigeminocerebellar projections in the cat.

Using the retrograde horseradish peroxidase technique, we have examined the distribution of labeled thalamic-, spinal- and cerebellar-projecting neurons in the trigeminal sensory nuclei of the cat. Injections into the nucleus ventralis posterior of the thalamus resulted in labeling of neurons in lamina I (subnucleus zonalis), the deeper part of lamina IV (the subnucleus magnocellularis) of the nucleus caudalis and in lamina V (the lateral extension of the nucleus medullae oblongatae centralis) on the contralateral side. A very large number of labeled small neurons were observed mainly in the caudal part of the nucleus interpolaris and in the ventral division of the principal sensory nucleus on the contralateral side and in the dorsal division of the principal sensory nucleus on the ipsilateral side. Injections into the known projection areas of the cerebellar cortex labeled mainly ipsilaterally the trigeminocerebellar neurons in a restricted ventrolateral area of lamina IV of the nucleus caudalis at its rostral level and in lamina V. Many labeled neurons were also observed in the nucleus interpolaris. Although the distribution overlapped with that of the trigeminothalamic neurons, the greatest majority were concentrated in its rostral part where the trigeminothalamic neurons were very small in number. In addition, labeled neurons were observed in the rostral part of the nucleus oralis and the ventralmost part of the ventral division of the principal sensory nucleus. No labeled neurons were observed in the dorsal division of the principal sensory nucleus and the mesencephalic nucleus. The trigeminospinal neurons were labeled mainly ipsilaterally following injections into the upper cervical cord. They were located in laminae I and III, the deeper part of lamina IV of the nucleus caudalis and in lamina V. Only scattered labeled neurons were found in the nucleus interpolaris. The number of labeled neurons increased in the nucleus oralis at the level of the superior olive. They tended to be distributed around or dorsal to the group of the trigeminothalamic neurons at the caudal part of the principal sensory nucleus. No neurons of the principal sensory nucleus appeared to project to the spinal cord. Based on the large size and location, the trigeminospinal neurons could be differentiated from the other projection neurons in the nucleus oralis. The present study demonstrates that the trigeminal sensory nuclei are composed of groups of neurons with different projections, since the main aggregations are localized at different levels. However, it should be examined whether the neuronal groups, which are labeled from the different structures in similar locations, are composed of individual neurons projecting to more than one of these structures.

A direct hypothalamic projection to the superior salivatory nucleus neurons in the rat. A study using anterograde autoradiographic and retrograde HRP methods

The location of the superior salivatory nucleus and terminal labelings of the hypothalamic descending fibers were demonstrated in the nucleus reticularis parvocellularis using HRP and the autoradiographic techniques, respectively. When both techniques were used in the same animals, some HRP-labeled neurons were seen among the accumulations of silver grains, suggesting pericellular terminations. The present study demonstrates that the hypothalamic efferents project directly to the superior salivatory nucleus innervating salivary and lacrimal glands.

Ascending and descending internuclear connections of the trigeminal sensory nuclei in the cat. A study with the retrograde and anterograde horseradish peroxidase technique

The distribution of cells of origin of ascending and descending internuclear connections in the trigeminal sensory nuclei was studied by the retrograde horseradish peroxidase technique in the cat. The termination of collaterals of these ascending axons was also studied by the anterograde transport of horseradish peroxidase. Following injections of horseradish peroxidase into the ventral part of the principal sensory nucleus and the adjacent reticular formation many small neurons were labeled ipsilaterally in the whole area of the caudal portion of the nucleus interpolaris and in laminae III and IV of the nucleus caudalis. Labeled neurons were also found in laminae I and V. Injections limited to either nucleus oralis, the ventral part of the principal sensory nucleus and the medial parabrachial nucleus labeled similar types of neurons in the above regions with a topographic relationship; neurons in the dorsal part of the nuclei caudalis and interpolaris project, dorsally, to rostral portions of the trigeminal sensory nuclei while those in the ventral part of the nuclei caudalis and interpolaris project ventrally. Anterograde labeling of axons arising from the nucleus caudalis demonstrates that the axons ascend in the intranuclear bundles and the adjacent reticular formation, and give off collaterals to the nuclei interpolaris and oralis, and the ventral part of the principal sensory nucleus. Injections limited to the nucleus caudalis labeled small neurons in the rostral portion of the nucleus oralis and the caudal portion of the nucleus interpolaris. The present study suggests that these ascending and descending internuclear connections of the trigeminal sensory nuclei may modulate transmission of afferent inputs to various projection sites, such as thalamus, superior colliculus, cerebellum and spinal cord.

A direct projection from the hypothalamus to the area postrema in the rat, as demonstrated by the HRP and autoradiographic methods

A direct hypothalamic afferent to the area postrema was found in the rat. After an injection of tritiated amino acids into the hypothalamus, labeled fibers and terminals were observed in the entire part of the area postrema, with dense patches of silver grains present in places. Cells of origin of this novel projection were identified with the retrograde horseradish peroxidase (HRP) method in the dorsal hypothalamic area at the most rostral level of the dorsomedial hypothalamic nucleus.

Spinocerebellar projection fields in the horizontal plane of lobules of the cerebellar anterior lobe in the cat: an anterograde wheat germ agglutinin-horseradish peroxidase study

Using the anterograde transport of wheat germ agglutinin-horseradish peroxidase in the cat, the projection fields of the spinocerebellar tracts were studied in the horizontal plane of lobules of the anterior lobe. The central cervical nucleus projected to 3 longitudinal areas in zone A and the medial part of zone B. The T4-T7 segments projected to two major longitudinal areas in zones A and B, and small areas in zones C1-D. The L2-L4 segments projected densely to longitudinal areas in zone A and broad band-like areas in zones B-D. The L5 and L6 segments projected mainly to less demarcated areas in apical parts of zones B-D. The findings suggest that the basic pattern of projection proper to each spinocerebellar tract is consistent in all lobules of termination.

The location of spinal projection neurons in the cerebellar nuclei (cerebellospinal tract neurons) of the cat. A study with the horseradish peroxidase technique.

The distribution of spinal projection neurons was studied in the cerebellar nuclei of the cat following injections of horseradish peroxidase (HRP) into the cervical, thoracic and lumbar cord. HRP-positive (labeled) neurons were found in the medial (fastigial) and the posterior interpositus nuclei on the side contralateral to the cervical injection, being most numberous in cases with injections between the C2 and the C3 segments. In the medial nucleus (M) labeled neurons were distributed in the central to the caudal portions, and there was a conspicuous group of labeled small neurons extending from the ventrolateral part to the intermediate zone between the M and the anterior interpositus nucleus. With an increasing number of medium-sized neurons, this neuronal group persisted caudally in a similar position, ventromedial to the posterior interpositus nucleus (IP). Labeled large neurons were seen in the medial third of the IP. In the two cases labeled neurons of medium and small sizes were equal in number, and the neurons of the IP constituted about 10% of the total number of the spinal projection neurons. The present study suggests that the neurons of the M and the IP, including those of the intermediate group located between the two, project the bulk of the crossed descending fibers as far caudally as the C2 and the C3 segments.