Neuropeptides as growth regulators.

The classical role of neuropeptides as fast-acting neurohumoral signallers has recently been challenged by the discovery that many neuropeptides are also growth factors stimulating slow-acting mitogenesis. Their mechanisms of action have been studied in cell culture, and their cell-surface receptors have been characterized pharmacologically using agonists and antagonists. We describe the mitogenic effects of bombesin, vasopressin, bradykinin and vasoactive intestinal peptide in murine fibroblasts. We suggest that the receptors for bombesin, vasopressin and bradykinin have more than one binding site, permitting modulation of transmitted signals. As these neuropeptide receptors share the ability to mobilize intracellular Ca2+, their common domain may be essential to G-protein coupling.