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 ?rst-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.