Discusses the modulation of the repulsive and attractive guidance of axons by extracellular guidance factors by extracellular second messengers cyclic nucleotides and calcium. Factors that may induce the attraction of Xenopus spinal neuron growth cones; Overview of the signaling on deleted-in-colorectal-cancer; Roles of cyclic adenosine monophosphate in netrin-1-mediated growth-cone guidance.