The role of calcium signaling in early axonal and dendritic morphogenesis of rat cerebral cortex neurons under non-stimulated growth conditions

The effects of depolarizing stimuli on neurite outgrowth have been shown to depend on an influx of extracellular calcium. However, the role of calcium under non-stimulated growth conditions is less well established. Here we i nvestigated the contribution of calcium signaling to early neuronal morphog enesis of rat cerebral cortex neurons at three levels by blocking L-type vo ltage sensitive calcium channels, by depleting intracellular calcium or by blocking myosin light chain kinase. Detailed quantitative morphological ana lysis of neurons treated for 1 day revealed that depletion of intracellular calcium strongly decreased the density of filopodia, arrested axonal outgr owth and strongly decreased dendritic branching. preventing calcium influx through L-type voltage sensitive calcium channels and blocking of myosin li ght chain kinase activity selectively decreased dendritic branching. Our ob servations support an essential role for basal intracellular calcium levels in axonal elongation. Furthermore, under non-stimulated conditions calcium entry through L-type voltage sensitive calcium channels and myosin light c hain kinase play an important role in dendritic branching. (C) 2001 Elsevie r Science B.V. All rights reserved.