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Altered circadian rhythm reentrainment to light phase shifts in rats with low brain angiotensinogen

Item Type:Article
Title:Altered circadian rhythm reentrainment to light phase shifts in rats with low brain angiotensinogen
Creators Name:Campos, L.A. and Plehm, R. and Cipolla-Neto, J. and Bader, M. and Baltatu, O.C.
Abstract:In this study, we aimed to investigate the adaptation of blood pressure (BP), heart rate (HR), and locomotor activity (LA) circadian rhythms to light cycle shift in transgenic rats with a deficit in brain angiotensin [TGR(ASrAOGEN)]. BP, HR, and LA were measured by telemetry. After baseline recordings (bLD), the light cycle was inverted by prolonging the light by 12 h and thereafter the dark period by 12 h, resulting in inverted dark-light (DL) or light-dark (LD) cycles. Toward that end, a 24-h dark was maintained for 14 days (free-running conditions). When light cycle was changed from bLD to DL, the acrophases (peak time of curve fitting) of BP, HR, and LA shifted to the new dark period in both SD and TGR(ASrAOGEN) rats. However, the readjustment of the BP and HR acrophases in TGR(ASrAOGEN) rats occurred significantly slower than SD rats. The LA acrophases changed similarly in both strains. When light cycle was changed from DL to LD by prolonging the dark period by 12 h, the reentrainment of BP and LA occurred faster than the previous shift in both strains. The readjustment of the BP and HR acrophases in TGR(ASrAOGEN) rats occurred significantly slower than SD rats. In free-running conditions, the circadian rhythms of the investigated parameters adapted in TGR(ASrAOGEN) and SD rats in a similar manner. These results demonstrate that the brain RAS plays an important role in mediating the effects of light cycle shifts on the circadian variation of BP and HR. The adaptive behavior of cardiovascular circadian rhythms depends on the initial direction of light-dark changes.
Keywords:Brain Renin-Angiotensin System, Heart Rate, Animals, Rats
Source:American Journal of Physiology Regulatory Integrative and Comparative Physiology
ISSN:0363-6119
Publisher:American Physiological Society (U.S.A.)
Volume:290
Number:4
Page Range:R1122-R1127
Date:1 April 2006
Official Publication:https://doi.org/10.1152/ajpregu.00703.2005
PubMed:View item in PubMed

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