The distribution of recurrent purkinje collateral synapses in the mouse cerebellar cortex: An electron microscopic study

Myelinated fibers found in the lower molecular layer of the mouse cerebellum form synaptic enlargements of a uniform morphological appearance. Similar synapses have been observed to come from myelinated fibers in the upper granularlower Purkinje cell layer. Both have been interpreted as Purkinje collateral boutons. The study of the distribution of Purkinje collateral synapses revealed that one third formed the supraganglionic plexus in the lower molecular layer and two thirds formed an infraganglionic plexus in the lower Purkinje upper granular zone. In the molecular layer, basket cell somata and dendrites received the gratest number of Purkinje collaterals, while Purkinje dendrites and branchlets received relatively few. In the infraganglionic plexus, the Purkinje collaterals terminated on “very low basket” cells and upon a dense dendritic “thicket” belived to be contributed largely by basket cells.