Calcium-binding proteins in primate cerebellum

Single and double antigen localization procedures were used to study the distribution of the calcium-binding proteins calretinin, calbindin and parvalbumin in the cerebellum of the squirrel monkey (Saimiri sciureus). The immunostaining experiments have revealed that each of the three calcium-binding proteins occurred, either alone or in various combinations, in many neuronal types of the monkey cerebellum, including the Purkinje cells. Immunoreactivity for calbindin was detected in virtually all Purkinje cells, whereas immunoreactivity for calretinin and parvalbumin was encountered only in some subpopulations of Purkinje cells. In the vermal region, parvalbumin immunostaining appeared in the form of typical weak and strong alternating parasagittal bands. Calretinin immunoreactivity was found in virtually all neurons and fiber systems related to the granular layer, including the monodendritic cells, the granule cells and their parallel fibers, the Golgi and Lugaro cells and the mossy fibers. The Golgi cells also displayed calbindin and parvalbumin immunoreactivity. Parvalbumin was found to labeled both the climbing and mossy fibers, as well as the basket and stellate cells lying in the molecular layer. These results reveal that virtually all the different neuronal types in the primate cerebellum contain at least one of three calcium-binding proteins investigated in the present study. Furthermore, calretinin appears to be a particularly reliable molecular maker for all the neuronal elements associated with the granular layer in the primate cerebellum.