Original research
Cardiac baroreflex is already blunted in eight weeks old spontaneously hypertensive rats
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* Corresponding author: Luiz C de Abreu luizcarlos@usp.br
1 Department of Morphology and Physiology, School of Medicine of ABC, Av. Príncipe de Gales, 821, Santo André 09060-650, Brazil
2 Department of Clinical Medicine, Cardiology Division, School of Medicine of ABC, Av. Príncipe de Gales, 821, Santo André 09060-650, Brazil
3 Department of Medicine, Cardiology Division Federal University of São Paulo (UNIFESP), Rua Napoleão de Barros, 715 Térreo, São Paulo 04039-032, Brazil
4 Department of Physiology, Federal University of São Paulo (UNIFESP), Rua Napoleão de Barros, 715 Térreo, São Paulo 04039-032, Brazil
5 Cardiovascular Surgery Division, School of Medicine of ABC, Av. Príncipe de Gales, 821, Santo André 09060-650, Brazil
6 Speech Pathology and Audiology Department, Faculty of Philosophy and Sciences, Paulista State University (UNESP), Av. Hygino Muzzi Filho, 737, Campus Universitário, Marília 17525-900, Brazil
International Archives of Medicine 2010, 3:2 doi:10.1186/1755-7682-3-2
Published: 27 January 2010Abstract
Background
The literature did not evidence yet with which age spontaneously hypertensive rats (SHR) start to present baroreflex reduction. We endeavored to evaluate the baroreflex function in eight-week-old SHR.
Methods
Male Wistar Kyoto (WKY) normotensive rats and SHR aged eight weeks were studied. Baroreflex was calculated as the variation of heart rate (HR) divided by the mean arterial pressure (MAP) variation (ΔHR/ΔMAP) tested with a depressor dose of sodium nitroprusside (SNP, 50 μg/kg) and with a pressor dose of phenylephrine (PHE, 8 μg/kg) in the right femoral venous approach through an inserted cannula in the animals. Significant differences for p < 0.05.
Results
Baseline MAP (p < 0.0001) and HR (p = 0.0028) was higher in SHR. Bradycardic peak was attenuated in SHR (p < 0.0001), baroreflex gain tested with PHE was also reduced in the SHR group (p = 0.0012). PHE-induced increase in MAP was increased in WKY compared to SHR (p = 0.039). Bradycardic reflex responses to intravenous PHE was decreased in SHR (p < 0.0001).
Conclusion
Eight weeks old SHR already presents impairment of the parasympathetic component of baroreflex.