Consequences of manganese intoxication on the circadian rest-activity rhythms in the rat. (7th September 2016)

• Record Type: Journal Article
• Authors: Bouabid, Safa; Fifel, Karim; Benazzouz, Abdelhamid; Lakhdar-Ghazal, Nouria
• Is Part Of: Neuroscience. Volume 331(2016)
• Page Start: 13
• Page End: 23
• Publication Date: 2016-09-07
• Subjects: 5-HT serotonin -- BG basal ganglia -- DA dopamine -- DD constant darkness -- LD light–dark -- Mn Manganese -- NE norepinephrine -- NHP non-human primate -- PD Parkinson's disease -- SCN suprachiasmatic nucleus -- SNpc substantia nigra pars compacta -- SWS slow wave sleep; manganese -- circadian rhythm -- rest-activity -- light–dark cycles -- entrainment -- Parkinsonism; Neurochemistry -- Periodicals; Neurophysiology -- Periodicals; Neurology -- Periodicals; Neurochimie -- Périodiques; Neurophysiologie -- Périodiques; Neurochemistry; Neurophysiology; Electronic journals; Periodicals; Electronic journals; 612.8
• DOI: 10.1016/j.neuroscience.2016.06.016
• Languages: English
• ISSNs: 0306-4522

Abstract

Highlights: Manganese induced alterations of the circadian pattern of rest-activity rhythm. Manganese treatment induced a more fragmented and less stable rest-activity rhythm. Manganese reduces the total amount of 24-h locomotor activity and the nocturnal activity. These deficits led to a significant decrease in the amplitude of the rest-activity rhythm. A 6-h advanced activity revealed abnormal entrainment to the new photoperiod after manganese. Abstract: 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 (10 mg/kg, i.p) for 5 weeks. Locomotor activity was assessed under a light–dark (LD) cycle, constant darkness (DD) and during adjustment to 6 h 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 ± 0.07 h in Mn group vs. 24.01 ± 0.04 h 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.