Identification of synapses formed in the cerebellar cortex by purkinje axon collaterals: an electron microscope study

Summary Purkinje axon collaterals and their synaptic terminals can be identified on the basis of three criteria: (1) They are the only myelinated axons of local elements, hence any myelinated axon persisting in chronically isolated folium is a Purkinje axon or its collateral; (2) They are the only known transfolial axons, so that axons and synapses found in the state of secondary degeneration after lesions placed into neighbouring folia of the cerebellar cortex are Purkinje axon collaterals and synapses; (3) The peculiar axonal tubular systems described by Andres (1965) are specific for Purkinje axons and their synaptic endings, which offers an additional clue for their identification. Using these three criteria numerous synapses of Purkinje axon collateral endings have been identified on the large Golgi neurons, both cell bodies and principal dendrites, and on the bodies of basket neurons. No evidence of the termination of Purkinje axon collaterals on other Purkinje cells could be detected.