Ryotaro Matsushima

Pretectal projections to the inferior olive in the rabbit

Abstract Direct pretectal projections to limited regions of the inferior olivary nucleus were found in the rabbit by means of the Nauta-Gygax and Fink-Heimer methods. The lesions were produced stereotaxically in the pretectal region of five rabbits. They encroached commonly upon the nucleus tractus opticus, the rostral half of the nucleus olivaris pretectalis, and involved some of the nucleus pretectalis posterior and anterior. Degeneration in the inferior olivary nucleus was found ipsilaterally in the dorsal cap and in the medial and dorsal aspects of the β-nucleus. Degeneration in the dorsal cap was marked and that in the β-nucleus was slight. Degenerated fibers terminating within these regions of the inferior olivary nucleus appeared to descend the brain stem ipsilaterally, mainly through the medial portions of the tegmentum, with no tendency to form compact fascicles. Based on the present and previous findings, it is presumed that the pretecto-olivary fibers provide a link of the pathways for the visual inputs to the vestibular nuclei and cerebellum.

Topographical representation of peripheral branches of the facial nerve within the facial nucleus: A HRP study in the cat

Representation of peripheral branches of the facial nerve within the facial nucleus of the cat was examined by utilizing retrograde axonal transport of horseradish peroxidase (HRP), which was injected into groups of muscles supplied by each of the main peripheral branches of the facial nerve. The cervical branch was represented in the ventromedial division of the facial nucleus, the posterior auricular branch in the medial division, the temporal branch in the intermediate division, the zygomatico-orbital branch in the dorsal division, the superior labial branch in the lateral division and the inferior labial branch in the ventrolateral division.

Topographical arrangement of hypoglossal motoneurons: An HRP study in the cat

Myotopical localization of hypoglossal motoneurons and representation of the main branches of the hypoglossal nerve within the hypoglossal nucleus were examined in the cat by the HRP method. The hypoglossal nucleus is divided cytoarchitectonically into the ventromedial and dorsolateral divisions; the medial and lateral branches of the hypoglossal nerve are represented respectively in the ventromedial and dorsolateral divisions. The genioglossus motoneurons are located in the ventrolateral part of the ventromedial division, and the geniohyoid motoneurons are in the most ventral part of the ventromedial division. The hypoglossus and styloglossus motoneurons are located in the lateral and dorsolateral parts of the dorsolateral division.

Topographical representation of masticatory muscles in the motor trigeminal nucleus in the rabbit: A HRP study

Myotopical localization of masticatory motoneurons was studied in rabbit by means of the horseradish peroxidase (HRP) method. As described by Meessen and Olszewsky [6], the motor trigeminal nucleus of rabbit is divided into 3 divisions; caudoventromedially alpha, rostroventromedially beta and dorsolaterally gamma nuclei. Within the alpha nucleus, the anterior digastric motoneurons are located ventromedially and the mylohyoid motoneurons dorsolaterally. Lateral pterygoid motoneurons are situated in the beta nucleus. Within the gamma nucleus, the temporal, masseter and medial pterygoid muscles are represented medially, centrally and ventrolaterally, respectively.

Direct amygdaloid projections to the dorsal motor nucleus of the vagus nerve: a light and electron microscopic study in the rat

The projections from the central nucleus of the amygdala to the dorsal vagal complex were examined in the rat by means of anterograde and retrograde axonal transport of wheat germ agglutinin-horseradish peroxidase and anterograde degeneration. Light microscopic findings confirmed that the amygdala projects to the dorsal motor nucleus (DMV) and the nucleus of the solitary tract. Electron microscopic experiments demonstrated degenerating axosomatic and axodendritic terminals in the DMV following electrolytic lesions in the central nucleus of the amygdala.

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.

Distribution of axons exhibiting both enkephalin- and serotonin-like immunoreactivities in the lumbar cord segments: an immunohistochemical study in the cat

Axons exhibiting both enkephalin- and serotonin-like immunoreactivities were observed by the double immunofluorescence method in the lumbar cord segments of the cat. Double-labeled axons were seen most frequently in laminae I, IIa and the lateral part of lamina V. They were also distributed in other parts of the dorsal horn and lamina X (especially in the dorsal part), but rarely found in laminae VII, VIII and IX. After cervical hemicordotomy the vast majority of double-labeled axons disappeared from the spinal gray ipsilateral to the lesion.

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.

Amygdalospinal projections in the macaque monkey

Injection of horseradish peroxidase into the cervical cord in the macaque monkey led to the retrograde labeling of neurons in the caudal part of the central nucleus of the amygdala ipsilateral to the spinal half where the injection was made. Although the number of labeled neurons in the amygdala was small, they were constantly found in 7 macaque monkeys (3 Japanese monkeys, 3 crab-eating monkeys and 1 rhesus monkey) which were injected with the enzyme into the upper and middle cervical cord segments.

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.