Generation of calcium signal in mammalian oligodendrocytes is a result of two different mechanisms, namely: (i) transmembrane calcium influx via voltage-operated calcium channels, and (ii) calcium release from IP3-sensitive internal calcium stores. The oligodendrocytes express two types of voltage-operated calcium channels with different voltage-dependence. The expression of calcium channels undergoes marked changes during the development of the oligodendrocytes. The cytoplasmic calcium release from internal depots can be triggered by the activation of P2 metabotropic purinoreceptors.