cerebellum, development, synaptogenesis, synaptophysin.The aim of the present work was to perform a qualitative and quantitative evaluation of synaptogenesis in the developing rat cerebellum (2-45 days after birth) by immunohistochemical detection of the marker synaptophysin (Syn). Syn expression was detected in postmitotic neurons in the external granular layer and migrating precursors of cerebellar granular neurons. The width of the synaptogenesis zone in the molecular layer increased throughout the study period, and this was accompanied by a decrease in Syn immunore-activity. There was also a reduction in the number of Syn-immunopositive synapses around the perikarya of Purkinje cells from day 7 to day 15. The inner granular layer showed Syn-immunopositive dots, whose sizes increased from day 2 to day 45, which was associated with the formation of cerebellar glomeruli. The nucleus interpositus of the cerebellum showed an increase in the number and size of axosomatic synapses around neuron perikarya throughout the study period. Uneven groupings of Syn-positive axodendritic syn¬apses appeared in the neuropil
