Some fine structural features of the neural elements composing the cerebellar nuclei in the cat.

Abstract

AbstractAll cerebellar nuclear areas examined contained neurons of several sizes. The smallest have cell bodies ranging from 8–15 μ in diameter in which the cytoplasm is sparse and the granular endoplasmic reticulum randomly distributed. The larger neurons range in diameter from 25–40 μ and the granular reticulum is highly organized and forms Nissl bodies.Axo‐somatic terminals occur on all neurons seen in the cerebellar nuclei but are randomly distributed and not usually juxtaposed on the cell surface. Several types of axo‐dendritic terminals were encountered. Those on small dendritic branches are characterized by asymmetric accumulations of electron dense material in the postsynaptic cytoplasm. They are also usually bounded by astrocytic glial processes. Terminals on large dendrites show long lengths of membrane apposition and discontinuity of synaptic contacts. A number of dendrites displayed spines upon which terminations occurred. Terminal boutons were also observed to arise from nodes of Ranvier.The neuropil surrounding the neurons of the cerebellar nuclei is filled with myelinated fibers of varying diameter, the smallest of which are about 0.4 μ. The latter often occupy positions close to the surface of neuronal cell bodies and dendrites. Only few unmyelinated fibers were observed.