Transient accumulations of glycosaminoglycans in rat and chicken cerebellar cortex during development

Modifications of glycosaminoglycans at neuropile of rat and chicken cerebellum during development were histochemically studied. The application of Alcian Blue staining techniques and enzymatic degradations permitted to reveal in both species that in earlier stages of cerebellar development hyaluronic acid is present throughout neuropile of entire cerebellum but it accumulated preferentially at the medullary region and around precursory Purkinje cells where it showed a mucoid-like appearance. This substance was related with cell migration and aligning processes. At the middle of cerebellar development, around 2nd postnatal week in rat and 12-16 embryonary days in chick, a new polyanionic transient accumulation, presumably chondroitinsulphate, became present at the medullary region following the longitudinal axis of folium and limiting the forming granular layer, being this substance mainly related with polarity processes by controlling or guiding the growing cones of afferent fibers, which enter massively to cerebellar cortex. It disappeared as myelination progressed. Also from the middle stage of development onward, beside glycosaminoglycans, other polyanionic substances were present at the molecular and granular layer neuropile and at the cytoplasm of some nerve cells. These macromolecules were rather related with nerve cell differentiation and maturation.