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Recio, Joaquín; Pévet, Paul; Masson‐Pévet, Mireille

Serotonergic Modulation of Photically Induced Increase in Melatonin Receptor Density and Fos Immunoreactivity in the Suprachiasmatic Nuclei of the Rat

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  • Medientyp: E-Artikel
  • Titel: Serotonergic Modulation of Photically Induced Increase in Melatonin Receptor Density and Fos Immunoreactivity in the Suprachiasmatic Nuclei of the Rat
  • Beteiligte: Recio, Joaquín; Pévet, Paul; Masson‐Pévet, Mireille
  • Erschienen: Wiley, 1996
  • Erschienen in: Journal of Neuroendocrinology
  • Sprache: Englisch
  • DOI: 10.1046/j.1365-2826.1996.02245.x
  • ISSN: 0953-8194; 1365-2826
  • Schlagwörter: Cellular and Molecular Neuroscience ; Endocrine and Autonomic Systems ; Endocrinology ; Endocrinology, Diabetes and Metabolism
  • Entstehung:
  • Anmerkungen:
  • Beschreibung: <jats:p>The mammalian suprachiasmatic nuclei (SCN) contain a circadian clock which is regulated by neuronal photic and non‐photic afferences. Among these, the serotonergic input originating from the dorsal raphe nucleus (DRN) is extremely important. In rats, a light pulse administered during the dark period is known to induce the expression of the immediate early gene c‐fos and to increase melatonin receptor density in the SCN. The aim of this study was to assess whether, in rats, these two phenomena were regulated by serotonin, acting via 5‐HT<jats:sub>1A</jats:sub> receptors. Three days after pinealectomy, 4 groups of rats were injected i.p. 90 min before sacrifice with respectively: (1) vehicle, (2) the 5‐HT<jats:sub>1A</jats:sub>‐agonist 8‐OH‐DPAT (5 mg/kg), (3) the 5‐HT<jats:sub>1A</jats:sub>‐antagonist NAN‐190 (10 mg/kg) or (4) NAN‐190 and then 8‐OH‐DPAT. Half of the animals from each group were exposed to light for 60 min before sacrifice and the other half remained in darkness. Sacrifice took place 5 to 6 h after lights off. Our results show that the antagonist NAN‐190: (1) completely blocked the photically‐induced increase of melatonin receptor density in the SCN, with an IC50=0.352±0.103 mg/kg, and (2) partially blocked (30%) the photic induction of Fos (the protein product of c‐fos) in the ventrolateral subdivision of the SCN. The agonist 8‐OH‐DPAT enhanced the photically‐induced increase of melatonin receptors by 10% and decreased the photically‐induced increase in Fos by 18%. Both drugs were devoid of any effect in non‐light‐exposed animals. From these results we may suggest that, in rats, there is a serotonergic control of the neuronal path driving photic information to the SCN. This regulation seems to occur through 5‐HT<jats:sub>1A</jats:sub> or 5‐HT<jats:sub>1A</jats:sub>‐like receptors.</jats:p>