NEW STRUCTURAL ASPECTS OF THE SYNAPTIC CONTACTS ON PURKINJE-CELLS IN AN ELASMOBRANCH CEREBELLUM

Nerve fibre contacts on Purkinje cell perikarya in the cerebellum of t he small-spotted dogfish (Scyliorhinus canicula) were studied using th e Cajal reduced silver technique, Golgi methods and electron microscop y. Silver staining revealed axons with thick swellings close to the ba se of Purkinje cells. Golgi methods demonstrated the presence of 'pinc ushions' of somatic spines on Purkinje cells. Electron microscopy reve aled flattened fibres that formed extensive synaptic contacts with the Purkinje cell 'pincushions'. It is proposed, on the basis of the ultr astructural features, that these fibres are climbing fibres. Their pos sible significance in terms of the evolution of cerebellar circuitry i s discussed.