Neuronal turning depends on the source, not the absolute level, of released calcium.
Axon guidance cues, such as netrin-1, stimulate growth cone turning by altering intracellular calcium levels. However, no simple correlation exists between the location of calcium increase within the growth cone and the direction of movement. Previous data suggested that the type of cell adhesion matrix influences the direction of movement.
Ooashi et al. tested the effects of calcium release in dorsal root ganglia neurons by uncaging NP-EGTA in a small region of the growth cone. Axons grown on N-cadherin or on L1 immunoglobulin superfamily protein turned toward the side of calcium release and exhibited an increase in cAMP. Blocking cAMP caused the cell to turn away from the stimulus....
