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International Journal of Hypertension
Volume 2011, Article ID 738689, 8 pages
http://dx.doi.org/10.4061/2011/738689
Research Article

Circadian Variations in Blood Pressure, Heart Rate, and HR-BP Cross-Correlation Coefficient during Progression of Diabetes Mellitus in Rat

1Department of Physiology, College of Medicine, University of Lagos, 12003 Lagos, Nigeria
2Department of Physiology, College of Medicine University of Kentucky, Lexington, KY 40536-0298, USA
3Lexington VA Medical Center and Department of Internal Medicine, College of Medicine University of Kentucky, Lexington, KY 40536-0298, USA

Received 16 January 2011; Accepted 10 February 2011

Academic Editor: Kazuko Masuo

Copyright © 2011 Chikodi N. Anigbogu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Circadian changes in cardiovascular function during the progression of diabetes mellitus in the diabetes prone rat (BBDP) (n=8) were studied. Age-matched diabetes-resistant rats (BBDR) served as controls. BP was recorded via telemetry in contiguous 4 hr time periods over 24 hours starting with 12 midnight to 4 am as period zero (P0). Prior to onset of diabetes BP was high at P0, peaked at P2, and then fell again at P3; BP and heart rate (HR) then increased gradually at P4 and leveled off at P5, thereby exhibiting a bipodal rhythm. These patterns changed during long-term diabetes. The cross-correlation coefficient of BP and HR was not significantly different across groups at onset, but it fell significantly at 9 months of duration of diabetes (BBDP: 0.39 ± 0.06; BBDR: 0.65 ± 0.03; P<.05). These results show that changes in circadian cardiovascular rhythms in diabetes mellitus became significant at the late stage of the disease.