Cardiac baroreflex is already blunted in eight weeks old spontaneously hypertensive rats

doi:10.1186/1755-7682-3-2

International Archives of Medicine

Volume 3

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Cisternas JR
Valenti VE
Alves TB
Ferreira C
Petenusso M
Breda JR
Pires AC
Tassi N
de Abreu LC

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Cisternas JR
Valenti VE
Alves TB
Ferreira C
Petenusso M
Breda JR
Pires AC
Tassi N
de Abreu LC
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Original research

Cardiac baroreflex is already blunted in eight weeks old spontaneously hypertensive rats

José R Cisternas¹ , Vitor E Valenti¹^,3 , Thales B Alves⁴ , Celso Ferreira²^,3 , Márcio Petenusso¹ , João R Breda⁵ , Adilson C Pires⁵ , Nadir Tassi⁶ and Luiz Carlos de Abreu¹

¹Department of Morphology and Physiology, School of Medicine of ABC, Av. Príncipe de Gales, 821, Santo André 09060-650, Brazil

²Department of Clinical Medicine, Cardiology Division, School of Medicine of ABC, Av. Príncipe de Gales, 821, Santo André 09060-650, Brazil

³Department of Medicine, Cardiology Division Federal University of São Paulo (UNIFESP), Rua Napoleão de Barros, 715 Térreo, São Paulo 04039-032, Brazil

⁴Department of Physiology, Federal University of São Paulo (UNIFESP), Rua Napoleão de Barros, 715 Térreo, São Paulo 04039-032, Brazil

⁵Cardiovascular Surgery Division, School of Medicine of ABC, Av. Príncipe de Gales, 821, Santo André 09060-650, Brazil

⁶Speech Pathology and Audiology Department, Faculty of Philosophy and Sciences, Paulista State University (UNESP), Av. Hygino Muzzi Filho, 737, Campus Universitário, Marília 17525-900, Brazil

author email corresponding author email

International Archives of Medicine 2010, 3:2doi:10.1186/1755-7682-3-2


Published:	27 January 2010

Abstract

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.