1. Ultrastructural plasticity in the rat suprachiasmatic nucleus. Possible involvement in clock entrainment
- Author
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Olivier Bosler, Fabienne Guillaumond, Denis Becquet, Clémence Girardet, Anne-Marie François-Bellan, Interactions cellulaires neuroendocriniennes (ICN), Université de la Méditerranée - Aix-Marseille 2-Centre National de la Recherche Scientifique (CNRS), Centre de recherche en neurobiologie - neurophysiologie de Marseille (CRN2M), Aix Marseille Université (AMU)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique Moléculaire (UMR 6624) (LPM), Centre National de la Recherche Scientifique (CNRS)-Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC), Université de Franche-Comté (UFC), and Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
Male ,Vasoactive intestinal peptide ,MESH: Neurons ,MESH: Rats, Sprague-Dawley ,MESH: Arginine Vasopressin ,Rats, Sprague-Dawley ,0302 clinical medicine ,Axon terminal ,MESH: Glial Fibrillary Acidic Protein ,MESH: Animals ,MESH: Neuronal Plasticity ,Axon ,Neurons ,0303 health sciences ,Neuronal Plasticity ,Glial fibrillary acidic protein ,Suprachiasmatic nucleus ,MESH: Vasoactive Intestinal Peptide ,MESH: Gene Expression Regulation ,Circadian Rhythm ,medicine.anatomical_structure ,Neurology ,Hypothalamus ,MESH: Microscopy, Electron, Transmission ,Suprachiasmatic Nucleus ,MESH: Neuroglia ,Neuroglia ,hormones, hormone substitutes, and hormone antagonists ,Vasoactive Intestinal Peptide ,medicine.medical_specialty ,MESH: Rats ,MESH: Suprachiasmatic Nucleus ,Biology ,MESH: Dendrites ,03 medical and health sciences ,Cellular and Molecular Neuroscience ,Microscopy, Electron, Transmission ,MESH: Analysis of Variance ,Internal medicine ,Glial Fibrillary Acidic Protein ,medicine ,Animals ,MESH: Circadian Rhythm ,Circadian rhythm ,[SDV.BBM.BC]Life Sciences [q-bio]/Biochemistry, Molecular Biology/Biochemistry [q-bio.BM] ,030304 developmental biology ,Analysis of Variance ,Dendrites ,MESH: Male ,Rats ,Arginine Vasopressin ,Endocrinology ,Gene Expression Regulation ,nervous system ,Light effects on circadian rhythm ,biology.protein ,sense organs ,030217 neurology & neurosurgery - Abstract
International audience; Circadian rhythms in mammals are synchronized to the light (L)/dark (D) cycle through messages relaying in the master clock, the suprachiasmatic nucleus of the hypothalamus (SCN). Here, we provide evidence that the SCN undergoes rhythmic ultrastructural rearrangements over the 24-h cycle characterized by day/night changes of the glial, axon terminal, and/or somato-dendritic coverage of neurons expressing arginine vasopressin (AVP) or vasoactive intestinal peptide (VIP), the two main sources of SCN efferents. At nighttime, we noted an increase in the glial coverage of the dendrites of the VIP neurons (+29%) that was concomitant with a decrease in the mean coverage of the somata (-36%) and dendrites (-43%) of these neurons by axon terminals. Conversely, glial coverage of the dendrites of AVP neurons decreased (-19%) with parallel increase in the extent of somatal (+96%) and dendritic (+52%) membrane appositions involving these neurons. These plastic events were concomitant with daily fluctuations in quantitative expression of glial fibrillary acidic protein (GFAP), which were then used as an index of structural plasticity. The GFAP rhythm appeared to be strictly dependent on light entrainment, indicating that structural reorganization of the SCN may subserve synchronization of the clock to the L/D cycle. Other results presented reinforced this view while showing that circulating glucocorticoid hormones, which are known to modulate photic entrainment, were required to maintain amplitude of the GFAP rhythm to normal values.
- Published
- 2007
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