Three-dimensional reconstruction and synaptic architecture of cerebellar glomeruli in the rat.

Cerebellar glomeruli of simple type were studied by quantitative morphological and stereological methods. It has been found that in one glomerulus the centrally located mossy terminal forms synaptic contacts with about 50 granule cell dendrites, all deriving from distinct granule cells. The three-dimensional reconstruction of the glomeruli revealed that the terminal portion of the dendrites, the so called digits, are elongated, thin processes. Synaptic contacts by mossy terminals are established exclusively on the dendritic digits. Although these digits are the main postsynaptic targets for the Golgi axon terminals as well, these inhibitory endings might also synapse with the proximal portion of the granule cell dendrites.