Abstract
Melatonin's pleiotropic actions begin from controlling day/night cycle and hypothalamic/pituitary axes to, for example, vasomotor effects, immunomodulation, antilipid effects, modulation of endocrine functions, direct and indirect antiapoptotic effects, interference with nitric oxide signaling, other antiexcitatory actions through ion channels and neurotransmitter systems, and most prominently the antioxidant activities which include expression of genes relevant to redox metabolism, including modulation of mitochondrial electron flux. Because of ubiquitous nature of the melatonin receptor, melatonin serves as pleiotropic molecule and its multiplicity of action goes beyond the established antioxidant activities. Melatonin exhibits pleiotropic effects essentially through four different mechanisms: binding to membrane receptors; nuclear receptors; intracellular proteins, and a receptor-independent radical scavenging function. The present review highlights some of the important pleiotropic effects of melatonin in human body.