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Endogenous melatonin provides an effective circadian message to both the suprachiasmatic nuclei and the pars tuberalis of the rat
Author(s) -
Agez Laurence,
Laurent Virginie,
Guerrero Hilda Y.,
Pévet Paul,
MassonPévet Mireille,
Gauer François
Publication year - 2009
Publication title -
journal of pineal research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.881
H-Index - 131
eISSN - 1600-079X
pISSN - 0742-3098
DOI - 10.1111/j.1600-079x.2008.00636.x
Subject(s) - melatonin , pinealectomy , circadian rhythm , medicine , endocrinology , suprachiasmatic nucleus , pineal gland , per1 , pars tuberalis , biology , endogeny , per2 , light effects on circadian rhythm , pinealocyte , circadian clock , hypothalamus , receptor , melatonin receptor , clock , pituitary gland , hormone
The suprachiasmatic nuclei (SCN) distribute the circadian neural message to the pineal gland which transforms it into a humoral circadian message, the nocturnal melatonin synthesis, which in turn modulates tissues expressing melatonin receptors such as the SCN or the pars tuberalis (PT). Nuclear orphan receptors (NOR), including rorβ and rev‐erbα , have been presented as functional links between the positive and negative loops of the molecular clock. Recent findings suggest that these NOR could be the initial targets of melatonin’s chronobiotic message within the SCN. We investigated the role of these NOR in the physiological effect of endogenous melatonin on these tissues. We monitored rorβ and rev‐erbα mRNA expression levels by quantitative in situ hybridization after pinealectomy. Pinealectomy had no effect on NOR circadian expression rhythms in the SCN in 8‐day pinealectomized (PX) animals. However in animals PX for 3 months, significant desynchronization between per1 and per2 transcription patterns appeared. These results suggest that endogenous melatonin could sustain the circadian rhythmicity and the phase relationship between the molecular partners of the SCN circadian system on a long‐term basis. On the other hand, pinealectomy decreased the level and abolished the rhythmicity of NOR mRNA expression in the PT. These effects were partially prevented by daily melatonin administration in the drinking water. These results show that NOR can be regulated by the melatonin circadian rhythm in the PT and could be the link between the physiological action of melatonin and the core of the molecular circadian clock in this tissue.