Color change: A non-invasive measure of melatonin action

Abstract

Research on melatonin's role in photoperiodic phenomena and the molecular mechanism of melatonin action would profit from understanding melatonin's action upon pigment cells and from incorporation of pigment cell and pelage parameters into experimental paradigms. Pigment cell activity is modified by melatonin through both direct and indirect mechanisms. Melatonin's influence upon physiological color change, i.e. the transfer of melanosomes in and out of melanophore processes, is the result of a direct effect upon the pigment cell. Melatonin's influence upon morphological color change, i.e. the transfer of pigment granules to surrounding cornified cells such as hair, is primarily mediated by melatonin-induced decreases in pituitary prolactin output, an indirect mechanism of action. Study of morphological color change is valuable to those interested in photoperiodic phenomena, whereas study of physiological color change is valuable to those interested in the molecular mechanism of melatonin action. This review details current concepts relevant to melatonin's role in both morphological and physiological color change. We also introduce the reader to pigment cell model systems available for study of melatonin action at the cellular level.