Cerebellar Granule Cells and Their Response to Radiation

Abstract

The granular layer of the cerebellar cortex situated between the molecular and medullary layers is built up mainly of the perikarya of small interneurons, the granule cells intermingled with part of their own processes, mossy fiber terminals, fibers of passage and other less numerous intrinsic cells. Ultrastructurally they are characterized by a nucleus which occupies most of the cell body and a rim of cytoplasm. The nucleus exhibits some aggregates of chromatin and in some cells a nucleolus. In the cytoplasm very scarce organelles are observed (Fig.l). Their main synaptic connections are found, first, at the cerebellar glomerulus where granule dendrites are seen in postsynaptic position towards mossy fiber rosettes. Desmosomic attachments are observed between granule dendrites. Second, at the level of the molecular layer where parallel fiber terminals (ramifications of the peripheral axon ) are seen apposing Purkinje dendrite spines.