Abstract

Effects of Circadian Rhythm Disruption on Cognitive Function and Related Expression of DREAM and Hyperphosphorylated Tau Protein in the Rat's Hippocampus

Introduction: Sleep deprivation has been demonstrated to impair the cognitive function associated with Downstream Regulatory Element Antagonistic Modulators (DREAM), Brain-derived neurotrophic factor (BDNF), and cAMP-response element binding (CREB) protein expression changes in rat hippocampus. This study was conducted to investigate whether Circadian rhythm Disruption (CD) has a similar mechanism with sleep deprivation on cognitive function and DREAM, Tau, and hyperphosphorylated Tau protein expression changes. Methods: 24 male Sprague Dawley rats were equally divided into 3 groups: (i) control (C), (ii) Acute CD (ACD), and (iii) Chronic CD (CCD). 1 cycle of the CD consists of phase-shifting, where daily light off was phased advanced three hours daily for 6 consecutive days followed by ten days of re-entrainment for recovery. The acute CD was induced by a single cycle. In contrast, the chronic CD was induced by 4 cycles of the CD. The C group was set in regular daily 12 hours light/dark. The rat's spatial learning and memory were measured by the Morris water maze test followed by immunohistochemistry analysis for protein expression. Results: There was no significant difference in escape latency during the acquisition trial and swim time in the target quadrant during the probe test between all groups. The hippocampus DREAM, Tau, and hyperphosphorylated Tau protein expression also were not statistically significant differences compared to all groups. Conclusion: We concluded that in this study, the CD has not adequately elicited changes in cognitive function and expression of the hippocampus DREAM, Tau, and hyperphosphorylated Tau proteins.

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