Cerebellar Purkinje cells have the most elaborate dendritic trees among neurons in the brain. Purkinje cell dendrites receive numerous glutamatergic synaptic inputs from granule cells, forming a main component of cerebellar neuronal circuitry. Ryanodine receptor (RyR), an intracellular calcium release channel, mediates calcium-induced calcium release in many types of cells including cerebellar Purkinje and granule cells. In regard to the expression pattern of RyR subtypes in the cerebellum, Purkinje cells show high expression of RyR type 1 (RyR1) in addition to lower expression of RyR type 2 (RyR2), whereas granule cells highly express RyR2. The expression level of RyR type 3 is very low in both Purkinje and granule cells. Recently, we showed that Purkinje cell-specific knockdown of RyR1 using single-cell electroporation of siRNA inhibited dendritic differentiation of Purkinje cells in cerebellar cell cultures. In addition, knockdown of RyR2 expressed by granule cells using a transfection reagent also inhibited dendritic differentiation of Purkinje cells. In the present study, we analyzed the role of RyR2 expressed by granule cells in dendritic differentiation of Purkinje cells in detail. Ryanodine (10 μM), a blocker of RyR, reduced the elevation of intracellular calcium concentration in both Purkinje and granule cells in response to glutamate stimulation and markedly inhibited dendritic differentiation of Purkinje cells in cerebellar cell cultures. ELISA analysis showed that ryanodine reduced the levels of brain-derived neurotrophic factor (BDNF) in the culture medium. When we added BDNF in addition to ryanodine into cultures, the ryanodine-induced inhibition of dendritic differentiation of Purkinje cells was partially rescued. In contrast, nerve growth factor did not rescue the ryanodine-induced inhibition of dendritic differentiation of Purkinje cells. In addition, ryanodine reduced glutamate release from granule cells after depolarization. These results suggest that dendritic differentiation of Purkinje cells is promoted not only by RyR1 expressed by Purkinje cells themselves, but also by RyR2 expressed by granule cells, through secretion of BDNF and glutamate from granule cells.