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Longitudinal assessment of the effects of oestrogen on blood pressure and cardiovascular autonomic activity in female rats
Author(s) -
ElMas Mahmoud M,
AbdelRahman Abdel A
Publication year - 2009
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.2009.05192.x
Subject(s) - medicine , baroreflex , endocrinology , blood pressure , ovariectomized rat , heart rate , hemodynamics , mean arterial pressure , autonomic nervous system , contractility , hormone
Summary1 Published data concerning the effects of ovarian hormones on haemodynamic variability are contradictory. For the first time, the present study used radiotelemetric haemodynamic monitoring to investigate the long‐term effects of chronic oestrogen depletion and repletion on cardiovascular autonomic control and arterial baroreflex sensitivity (BRS) in female rats. 2 Blood pressure (BP), heart rate (HR) and +dP/dt max of arterial pressure (an estimate of myocardial contractility) were monitored in sham‐operated (SO), ovariectomized (OVX) and oestrogen‐replaced OVX rats (OVXE2) for 16 weeks. Cardiovascular autonomic control and baroreflexes were assessed by frequency domain analysis of interbeat intervals (IBI) and systolic BP (SBP). 3 Compared with SO rats, OVX rats exhibited no changes in BP, short‐lived decreases in HR and sustained reductions in +dP/dt max of arterial pressure. The high‐ (HF; 0.75–3 Hz) and low‐frequency (LF; 0.25–0.75 Hz) components of spectral power of IBI were significantly decreased and increased, respectively, by ovariectomy. An increase in the IBI LF/HF ratio in OVX rats suggests a shift in the cardiac sympathovagal balance towards sympathetic dominance. Index α, the spectral index of spontaneous BRS, was reduced by OVX. 4 Oestrogen replacement caused significant reductions in BP and HR and reversed OVX‐induced changes in +dP/dt max of arterial pressure and cardiac autonomic activity. The LF oscillations of SBP were reduced in OVXE2 rats, suggesting a reduction in vascular sympathetic tone by oestrogen. 5 These findings highlight the importance of long‐term oestrogen therapy in rectifying the detrimental effects of depletion of ovarian hormones on the cardiovascular system and baroreflex.