Suprachiasmatic control of melatonin synthesis in rats: Inhibitory and stimulatory mechanisms
Por:
Perreau-Lenz S., Kalsbeek A., Garidou M.-L., Wortel J., Van Der Vliet J., Van Heijningen C., Simonneaux V., Pévet P., Buijs R.M.
Publicada:
1 ene 2003
Resumen:
The suprachiasmatic nucleus (SCN) controls the circadian rhythm of melatonin synthesis in the mammalian pineal gland by a multisynaptic pathway including, successively, preautonomic neurons of the paraventricular nucleus (PVN), sympathetic preganglionic neurons in the spinal cord and noradrenergic neurons of the superior cervical ganglion (SCG). In order to clarify the role of each of these structures in the generation of the melatonin synthesis rhythm, we first investigated the day- and night-time capacity of the rat pineal gland to produce melatonin after bilateral SCN lesions, PVN lesions or SCG removal, by measurements of arylalkylamine N-acetyltransferase (AA-NAT) gene expression and pineal melatonin content. In addition, we followed the endogenous 48 h-pattern of melatonin secretion in SCN-lesioned vs. intact rats, by microdialysis in the pineal gland. Corticosterone content was measured in the same dialysates to assess the SCN lesions effectiveness. All treatments completely eliminated the day/night difference in melatonin synthesis. In PVN-lesioned and ganglionectomised rats, AA-NAT levels and pineal melatonin content were low (i.e. 12% of night-time control levels) for both day- and night-time periods. In SCN-lesioned rats, AA-NAT levels were intermediate (i.e. 30% of night-time control levels) and the 48-h secretion of melatonin presented constant levels not exceeding 20% of night-time control levels. The present results show that ablation of the SCN not only removes an inhibitory input but also a stimulatory input to the melatonin rhythm generating system. Combination of inhibitory and stimulatory SCN outputs could be of a great interest for the mechanism of adaptation to day-length (i.e. adaptation to seasons).
Filiaciones:
Perreau-Lenz S.:
Netherlands Inst. for Brain Research, Meibergdreef 33, 1105 AZ Amsterdam, Netherlands
Neurobiologie des Rythmes, UMR ULP-CNRS 7518, Strasbourg, France
Kalsbeek A.:
Netherlands Inst. for Brain Research, Meibergdreef 33, 1105 AZ Amsterdam, Netherlands
Garidou M.-L.:
Neurobiologie des Rythmes, UMR ULP-CNRS 7518, Strasbourg, France
Wortel J.:
Netherlands Inst. for Brain Research, Meibergdreef 33, 1105 AZ Amsterdam, Netherlands
Van Der Vliet J.:
Netherlands Inst. for Brain Research, Meibergdreef 33, 1105 AZ Amsterdam, Netherlands
Van Heijningen C.:
Netherlands Inst. for Brain Research, Meibergdreef 33, 1105 AZ Amsterdam, Netherlands
Simonneaux V.:
Neurobiologie des Rythmes, UMR ULP-CNRS 7518, Strasbourg, France
Pévet P.:
Neurobiologie des Rythmes, UMR ULP-CNRS 7518, Strasbourg, France
Buijs R.M.:
Netherlands Inst. for Brain Research, Meibergdreef 33, 1105 AZ Amsterdam, Netherlands
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