Expression of membrane and nuclear melatonin receptors in mouse peripheral organs

Previous studies have shown that melatonin acts through specific receptors, including MT1 and MT2 membrane receptors as well as a nuclear receptor belonging to the orphan nuclear receptor family. Therefore, the goal of this study was to determine whether melatonin receptors mRNA is expressed in mouse peripheral tissues. To study the different receptors subtype expression, we have used a reverse-transcription polymerase chain reaction (RT-PCR) procedure followed by Southern hybridization with specific digoxigenin-labeled probes. RT-PCR studies revealed the presence of both MT1 membrane receptors and ROR(alpha)1 nuclear receptors in all the peripheral tissues examined (brain, heart, lung, liver and kidney). Moreover, the expression of ROR(alpha)1 nuclear receptors was also demonstrated by Western-blot. In contrast, expression of MT2 membrane receptors was only observed in brain and lung. These results suggest that melatonin, acting through its different subtypes receptors, plays a role in the neuroendocrine regulation of peripheral tissues function. (C) 2004 Elsevier Inc. All rights reserved.