Regulation of developing myelin sheath elongation by oligodendrocyte calcium transients in vivo

How action potentials regulate myelination by oligodendrocytes is uncertain. We show that neuronal activity raises [Ca²⁺]_i in developing oligodendrocytes in vivo and that myelin sheath elongation is promoted by a high frequency of [Ca²⁺]_i transients and prevented by [Ca²⁺]_i buffering. Sheath elongation occurs ~1 h after [Ca²⁺]_i elevation. Sheath shortening is associated with a low frequency of [Ca²⁺]_i transients but with longer duration [Ca²⁺]_i bursts. Thus, [Ca²⁺]_i controls myelin sheath development.