Yukihiko Yasui

Non-dopaminergic neurons in the substantia nigra project to the reticular formation around the trigeminal motor nucleus in the rat.

The dorsolateral part of the substantia nigra (SN) of the rat was observed to send projection fibers to the reticular formation (RF) around the trigeminal motor nucleus (Vm), bilaterally with a clear-cut ipsilateral dominance, by the anterograde and retrograde tracing techniques with PHA-L and WGA-HRP. A combination of retrograde tracing and immunohistochemistry for tyrosine hydroxylase (TH) revealed that no SN neurons sending their axons to the RF around the Vm showed TH-like immunoreactivity.

Non-dopaminergic projections from the substantia nigra pars lateralis to the inferior colliculus in the rat

The substantia nigra pars lateralis (SNI) of the rat was found, by the anterograde and retrograde tracing methods, to send projection fibers to the peripheral shell region surrounding the central nucleus of the inferior colliculus (IC), bilaterally with a clear-cut ipsilateral dominance. SNI neurons sending their axons to the IC were distributed throughout the entire rostrocaudal extent of the SNI. None of these SNI neurons showed tyrosine hydroxylase-like immunoreactivity.

Descending projections from the subparafascicular thalamic nucleus to the lower brain stem in the rat

SummaryIn the course of our study on the neuronal connections of the subparafascicular nucleus (SPF) in the rat, descending projections from the SPF to the lower brain stem were examined by using the anterograde tracer PHA-L (Phaseolus vulgaris leukoagglutinin) and retrograde tracer WGA-HRP (horseradish peroxidase conjugated to wheat germ agglutinin). When PHA-L was injected into the magnocellular and/or parvicellular division of the SPF (SPFm and/or SPFp), presumed terminal labeling was seen, bilaterally with an ipsilateral dominance, in the mesencephalic and pontine central gray matter, peripheral shell regions of the inferior colliculus, cuneiform nucleus, and superior olivary complex (mainly in the superior paraolivary nucleus, and additionally in the nuclei of the trapezoid body). A few labeled axon terminals were also seen in the cochlear nuclei bilaterally with a contralateral dominance. In the second set of experiments, WGA-HRP was injected into the inferior colliculus, superior olivary complex, or cochlear nuclei. When WGA-HRP was injected into the peripheral shell regions of the inferior colliculus or the superior olivary complex, many labeled neuronal cell bodies were seen in the SPFm bilaterally with an ipsilateral dominance, and a moderate number of labeled neuronal cell bodies were observed in the SPFp (lateral SPF) bilaterally with an ipsilateral dominance. When WGA-HRP was injected into the cochlear nuclei, a moderate number of labeled neuronal cell bodies were observed in the SPFm and SPFp bilaterally with a contralateral dominance. The results indicate that the SPFm and SPFp (lateral SPF) of the rat send a considerable number of projection fibers to the lower brain stem. The target regions of these projection fibers include the auditory relay nuclei, such as the inferior colliculus, superior olivary complex, and cochlear nuclei.

The subparafascicular thalamic nucleus of the rat receives projection fibers from the inferior colliculus and auditory cortex

The sources of afferent fibers to the subparafascicular thalamic nucleus (SPF) of the rat were investigated by the retrograde WGA-HRP and anterograde PHA-L methods. Layer V of the areas 3, 1 and 2 of the temporal cortex as well as the dorsal and external cortices of the inferior colliculus were found to send projection fibers to the whole rostrocaudal extent of the SPF bilaterally with a clear-cut ipsilateral dominance. The results indicate that the SPF of the rat may constitute a relay nucleus in the central auditory pathways.

Direct projections from the globus pallidus to the inferior colliculus in the rat.

A retrograde and anterograde wheat germ agglutinin-horseradish peroxidase (WGA-HRP) study in the rat indicated that some neurons in the globus pallidus (GP) sent their axons ipsilaterally to the inferior colliculus (IC). These neuronal cell bodies were located in the ventrolateral portions of the caudal part of the GP, and their axons were distributed mainly in the peripheral region of the external cortex of the IC.

Single retina ganglion cells sending axon collaterals to the bilateral superior colliculi: a fluorescent retrograde double-labeling study in the Japanese monkey (Macaca fuscata)

Single retinal ganglion cells projecting bilaterally to the superior colliculi (SC) by way of axon collaterals were revealed in the Japanese monkey (Macaca fuscata). After injecting Fast blue into the SC on one side and Diamidino yellow into the SC on the opposite side, some retinal ganglion cells were double-labeled with both tracers. Most of them were large cells (more than 25 microns in diameter), and were localized in a narrow strip around the vertical meridian of the retina on each side. This retinal area roughly corresponds to the reported strip of nasotemporal overlap, where both crossed and uncrossed retinofugal projections arise.

Neurons in the intertrigeminal region of the rat send projection fibers to the superior colliculus

A retrograde WGA-HRP and anterograde PHA-L study in the rat indicated that many neurons in the intertrigeminal region (ITR) sent their axons to the superior colliculus (SC), bilaterally with a clear-cut contralateral dominance. These neurons were small to medium in size and their axons terminated in the lateral part of the SC, especially in the stratum griseum intermedium.

Pallidal Afferents to the Neurons in the Anterior Thalamic Reticular Nucleus Projecting to the Centromedian Nucleus

The thalamic reticular nucleus is a thin layer of neurons interposed between the internal capsule laterally and the external medullary lamina medially, and covers the rostral and lateral aspects of the thalamus. This nucleus receives inputs from collaterals of both corticothalamic and thalamocortical axons (Jones, 1985). Cells of this nucleus in turn send their axons back into the thalamus, and innervate both relay cells and local GABAergic interneurons (for review see Steriade and Deschenes, 1984).

Immunohistochemical and electron microscopic studies of substance P in guinea pig nasal glands

The distribution of substance P-like immunoreactive (SP-IR) nerve endings in the nasal gland of the guinea pig was studied by using histochemical techniques to detect mucous glycoprotein and immunohistochemical techniques for SP, in combination with electron microscopy. Most nasal glands were negative for both AB and periodic acid-Schiff (PAS) staining. The SP-IR nerve fibers were found to form a network around these glands. The SP-IR nerve endings were located in the region between interdigitated cytoplasmic folds of acinar cells and along the cell surface, as well as in the intercellular spaces of proximal ducts. The acini which closely contacted with SP-IR nerve endings were serous in type. Our results suggest that substance P may contribute to the regulation of serous gland secretion in the guinea pig nasal mucosa.