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BioMed Research International
Volume 2014, Article ID 654710, 10 pages
Research Article

Regulation of Melanopsins and Per1 by α-MSH and Melatonin in Photosensitive Xenopus laevis Melanophores

1Department of Physiology, Institute of Biosciences, University of São Paulo, R. do Matão, Travessera 14, No. 101, 05508-900 São Paulo, SP, Brazil
2Department of Physiology, Institute of Biological Sciences, Federal University of Minas Gerais, 31270-901 Belo Horizonte, MG, Brazil

Received 26 January 2014; Revised 27 March 2014; Accepted 30 March 2014; Published 13 May 2014

Academic Editor: Mario Guido

Copyright © 2014 Maria Nathália de Carvalho Magalhães Moraes et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


α-MSH and light exert a dispersing effect on pigment granules of Xenopus laevis melanophores; however, the intracellular signaling pathways are different. Melatonin, a hormone that functions as an internal signal of darkness for the organism, has opposite effects, aggregating the melanin granules. Because light functions as an important synchronizing signal for circadian rhythms, we further investigated the effects of both hormones on genes related to the circadian system, namely, Per1 (one of the clock genes) and the melanopsins, Opn4x and Opn4m (photopigments). Per1 showed temporal oscillations, regardless of the presence of melatonin or α-MSH, which slightly inhibited its expression. Melatonin effects on melanopsins depend on the time of application: if applied in the photophase it dramatically decreased Opn4x and Opn4m expressions, and abolished their temporal oscillations, opposite to α-MSH, which increased the melanopsins’ expressions. Our results demonstrate that unlike what has been reported for other peripheral clocks and cultured cells, medium changes or hormones do not play a major role in synchronizing the Xenopus melanophore population. This difference is probably due to the fact that X. laevis melanophores possess functional photopigments (melanopsins) that enable these cells to primarily respond to light, which triggers melanin dispersion and modulates gene expression.