Evidence for melatonin synthesis in the rat brain during development
Article first published online: 12 DEC 2006
Journal of Pineal Research
Volume 42, Issue 3, pages 240–246, April 2007
How to Cite
Jimenez-Jorge, S., Guerrero, J. M., Jimenez-Caliani, A. J., Naranjo, M. C., Lardone, P. J., Carrillo-Vico, A., Osuna, C. and Molinero, P. (2007), Evidence for melatonin synthesis in the rat brain during development. Journal of Pineal Research, 42: 240–246. doi: 10.1111/j.1600-079X.2006.00411.x
- Issue published online: 12 DEC 2006
- Article first published online: 12 DEC 2006
- Received August 8, 2006; accepted November 8, 2006.
- embryonic development;
Abstract: Melatonin production is not restricted to the pineal gland. Several extrapineal sources of this indole such as retina, Harderian gland, and immune system are well documented. Melatonin of pineal origin is not present in the rat at early stages of development. To assess the potential capacity of local melatonin synthesis by the immature brain and to gain insight into the relationship between melatonin production by the brain (without the pineal gland) and pineal gland during rat development, the melatonin content as well as the expression and activity of the melatonin-synthesizing enzymes, N-acetyltransferase (NAT) and hydroxyindole-O-methyltransferase (HIOMT), were studied at fetal and postnatal stages. Moreover, melatonin-membrane receptor (MT1) expression was also analyzed. Both, the expression and activity of NAT and HIOMT were found in the brain with significant day/night differences in enzymes activities. Additionally, melatonin content was detected in all stages showing day/night differences depending on the stage of development. The brain nocturnal melatonin content was higher than diurnal content on postnatal day 16 and in adult rats which is in accordance with the pineal melatonin synthesis. To investigate the origin of this brain melatonin, pinealectomized rats were used and we found that the developing brain produced its own melatonin. Also, MT1 expression was detected in brain during development. These results demonstrate that, when the pineal is not yet producing melatonin, there is melatonin synthesis by the brain that could be used as protection from free radical damage and/or could exert some actions through MT1 receptors.