Neuroendocrine signalling: Natural variations on a Ca2+ theme

This special issue on Ca2+ signalling in neuroendocrine cells is an opportunity to assess, through a range of first-class review articles, the complex world of endocrine signalling, a complexity that is probably best captured by calling it “diversity in unity”. The unity comes from the fact that all the endocrine cells are excitable cells, able to generate action potentials and are using Ca2+ as an essential informational molecule, coupling cell stimulation with the activation of secretion, through the exocytotic process. The 'diversity' element, illustrated by almost all the reviews, stems from the modalities employed to achieve the increase in cytosolic Ca2+ signal, the balance between the participation of Ca2+ entry through the plasma membrane voltage-operated Ca2+ channels and the release of Ca2+ from intracellular Ca2+ stores, and the cross-talk between the Ca2+ and cyclic AMP signalling pathways.