Consequences of manganese intoxication on the circadian rest-activity rhythms in the rat
Neuroscience. 2016-09-01; 331: 13-23
DOI: 10.1016/j.neuroscience.2016.06.016
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Bouabid S(1), Fifel K(2), Benazzouz A(3), Lakhdar-Ghazal N(4).
Author information:
(1)University Mohamed V, Faculty of Sciences, Unit of Research on Biological
Rhythms and Environment, Rabat, Morocco.
(2)Laboratory of Neurophysiology, Molecular Cell Biology Department, Leiden
University Medical Center, PO Box 9600 Mailbox S5-P, 2300 RC Leiden, The
Netherlands.
(3)Université de Bordeaux, Institut des Maladies Neurodégénératives, UMR 5293,
Bordeaux, France; CNRS, Institut des Maladies Neurodégénératives, UMR 5293,
Bordeaux, France.
(4)University Mohamed V, Faculty of Sciences, Unit of Research on Biological
Rhythms and Environment, Rabat, Morocco. Electronic address:
.
Manganese (Mn) intoxication is associated with neurological dysfunctions
collectively known as Parkinsonism or Manganism. Like in Parkinson’s disease,
Manganism is associated with motor disturbances, together with non-motor
symptoms including cognitive and neuropsychiatric deficits. Although sleep
dysfunctions are commonly reported among workers exposed to Mn, their underlying
pathophysiology remains unknown. In this study, we investigated the
rest-activity rhythms in rats treated daily with MnCl2 (10mg/kg, i.p) for
5weeks. Locomotor activity was assessed under a light-dark (LD) cycle, constant
darkness (DD) and during adjustment to 6h shifts of the LD cycle. In LD
conditions, Mn-treated rats exhibited a more fragmented and less stable
rest-activity rhythm in addition to a reduction in the total 24-h amount of
locomotor activity as well as in the activity confined to the active dark phase
of the LD. Consequently, a significant decrease in the amplitude of the
rest-activity rhythm was observed. These disturbances were displayed during and
after Mn treatment. Furthermore, after the 6-h phase advance of the LD cycle,
Mn-treated rats failed to re-adjust accurately their behavioral activity to the
new shifted LD cycle. Upon release from LD into DD, Mn-treated rats expressed a
normal and stable free-running period of their rest-activity rhythm (23.92±0.07h
in Mn group vs. 24.01±0.04h in control rats). However, their rest-activity
rhythm remained highly fragmented and less stable. Our results provide the first
evidence that chronic Mn intoxication leads to impairment of rest-activity
rhythms in addition to the motor and non-motor disturbances reported in
Manganism.
Copyright © 2016 IBRO. Published by Elsevier Ltd. All rights reserved.
DOI: 10.1016/j.neuroscience.2016.06.016
PMID: 27316552 [Indexed for MEDLINE]