Structural Organization of the Fastigial Nucleus. In: Palay SL, Chan-palay V, editors. The Cerebellum—New Vistas. Berlin: Springer Berlin Heidelberg; 1982. pp. 233-49. [DOI: 10.1007/978-3-642-68560-6_12]

Fastigial nucleus projections in the midbrain and thalamus in dogs

Efferent connections to midbrain and thalamus from portions of the cerebellar fastigial nucleus were investigated using autoradiographic techniques. Bipolar stimulating electrodes were placed in the fastigial nucleus of anesthetized beagles and the area which produced maximal increases in blood pressure and heart rate was localized in each dog. A mixture of [3H]leucine and [3H]proline (4:1) was injected into that area and autoradiograms were prepared. Injections filled the rostral and various parts of the caudal fastigial nucleus. The rostral-caudal extent of injection sites were mapped in the horizontal plane from sequential coronal, thionin-stained sections and "primary" and "secondary" injection zones were defined according to specific criteria. Labeled axons reached the mesencephalon via the contralateral uncinate fasiculus. Ascending fibers assembled in a diffuse contingent at the prerubral level adjacent to the ventrolateral periaqueductal gray. The heaviest projections were contralateral to the injection site, but ipsilateral terminals were observed as well. In the midbrain, axons entered the contralateral and ipsilateral superior colliculus to branch repeatedly and terminate in the deep and intermediate layers. Additional terminals were observed bilaterally in the nuclei of the posterior commissure and pretectal areas at the midbrain-diencephalic junction. In the thalamus, labeled axons formed into three groups which terminated in: the contralateral paraventricular complex and medial dorsal nucleus; the contralateral central medial, paracentral, parafasicular and central lateral nuclei, and the contralateral ventral medial and ventral lateral nuclei. There was a sparse projection to the ipsilateral ventral lateral nucleus. The contralateral projection to the ventral medial and ventral lateral nuclei was marked by dense clusters of label ventral to the internal medullary lamina extending, in the dorsal ventral lateral nucleus, to its rostral pole. Projections to specific somesthetic thalamus or the hypothalamus were not observed. These ascending projections in the canine brain generally conform to those described in other nonprimate mammals. The fastigial nucleus presumably provides information concerning equilibrium and body proprioception to the superior colliculus and to thalamic nuclei including both specific motor relay and "nonspecific" midline and intralaminar nuclei, much the same as reported in the cat. The projection to the ventral medial and ventral lateral thalamic nuclei terminate in areas known to participate in the control of axial and proximal limb muscle activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Localization of serotonin immunoreactivity in the opossum cerebellum

We have used the indirect antibody peroxidase-antiperoxidase technique to analyze the course of serotonin (5-hydroxytryptamine; 5HT) fibers to the deep cerebellar nuclei; the distribution of serotonin within the nuclei; the continued course of 5HT fibers to the cerebellar cortex; and the lobular and laminar distribution of this indoleamine in the cerebellar cortex. Only rarely are fibers found in either the restiform body or the brachium pontis. However, a distinct bundle of serotoninergic axons is present in the medial aspect of the brachium conjunctivum. Axons arise from this bundle and course dorsally into the neuropil of the deep cerebellar nuclei. The densest immunostaining is present in posterior and ventral regions of all four cerebellar nuclei. Within the nuclei large (24% of total) and small (76% of total) varicosities are present. The average distance between varicosities on individual axons is 3.85 micron (S.D. = 1.2). The innervation of the cerebellar cortex is derived primarily from fibers that course through the deep nuclei. At levels caudal to the deep nuclei a single midsagittal band courses into lobules VIII and IX. In the cerebellar cortex, serotoninergic axons and varicosities are present in all lobules; however, the fiber density is not uniform. The densest distribution is present in vermal lobule VIII and the dorsal folia of lobule IX. Within the granule cell layer of lobules VIII and IX, immunoreactive elements form a midsagittal band, and to a lesser degree, two parasagittal bands. Beaded serotoninergic fibers course through the deep and middle portion of the granule cell layer and give rise to a plexus at the border between the Purkinje cell and granule cell layers. Within this plexus axons extend long distances in the transverse and sagittal planes. Long beaded axons oriented in the transverse plane of the folia are also present in the deep molecular layer. A few radial serotoninergic fibers ascend to the pial surface and give rise to very short tangential branches. In all three cortical layers, both large (19% of total) and small (81% of total) varicosities are present. The average distance between varicosities on individual fibers is 5.3 micron (S.D. = 2.2).(ABSTRACT TRUNCATED AT 400 WORDS)