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.