Autonomic Nervous System and Cardiovascular Variability in Rats: a Spectral Analysis Approach

Mechanisms underlying systolic (SBP) and diastolic (DBP) blood pressure and heart rate (HR) beat-to-beat variability were investigated using spectral analysis in conscious genetically normotensive (LN) and hypertensive (LH) adult rats from the Lyon strains. In LN rats, basal SBP, DBP, and HR spectra exhibited peaks in low (LF: 0.38-0.45 Hz) and high (HF: 1.04-1.13 Hz) frequencies. The LF peak of SBP, and even more of DBP, could be attributed to the influence of the sympathetic nervous system as it disappeared after destruction of the sympathetic nerves or a combined alpha- and beta-adrenoceptor blockade, whereas it was higher after blockade of the parasympathetic system. The HF peak of HR, linked to the respiratory rate, was abolished by the parasympathetic system blockade, whereas those of SBP and DBP were enhanced. In LH rats, which exhibit a lower sympathetic activity, the LF peaks of SBP and DBP were less distinct compared with LN controls. We conclude that the LF peak of DBP and the HF peak of HR are likely to represent useful estimates of the sympathetic vascular control and of the parasympathetic cardiac control, respectively.