Calcium-binding protein immunocytochemistry in organotypic cultures of cerebellum.

Vitamin D-dependent calcium-binding protein is known to be present in specific classes of neurons including Purkinje cells of the rat and chick. Explant cultures of newborn mouse cerebellum consisting of cerebellar cortex and deep nuclear region were fixed at maturity (20 days in vitro). Paraffin sections were reacted with the antiserum to purified chick duodenal calcium-binding protein. The Purkinje cell of these cultures reacted in its entirety--neuronal soma, dendrite, axon and terminals (in the deep nuclear region). The results verified many of the findings of our previous morphological studies. Qualitatively similar results were obtained with cultures maintained either in medium containing serum and embryo-extract or in a defined medium. There is not yet sufficient data to indicate whether this protein in the neurons in culture is dependent upon an exogenous source of vitamin D. This immocytochemical marker should prove useful to identify a specific neuron-type in culture.