Power spectral analysis of short-term RR interval and arterial blood pressure oscillations in lizard ( Gallotia galloti): Effects of parasympathetic blockade

Abstract

Spontaneous short-term oscillations in consecutive beat-to-beat RR interval (RRI) and systolic blood pressure (SBP) values of lizards ( Gallotia galloti) in basal conditions and under parasympathetic blockade with atropine at 23°C body temperature were investigated using spectral analysis. In control conditions, both RRI and SBP spectra exhibited two major oscillations in very low (VLF 0.008–0.030 Hz) and low (LF 0.030–0.100 Hz) frequencies. Most lizards presented a high frequency (HF) respiratory peak in the SBP spectra whenever the lizard's ventilatory pattern was rhythmic. Parasympathetic blockade decreased all RRI oscillations and LF and HF oscillationsof SBP. VLF and LF oscillations of RRI and SBP were still clearly present after blockade, which shows that other neural or humoral systems different from parasympathetic could mediate also low frequency RRI and SBP variability. SBP-RRI cross-spectral analysis showed in control conditions a linear relationship between SBP and RRI variations in the VLF, LF and HF bands, with SBP variations leading RRI; the parasympathetic limb of the baroreflex seems to be involved in maintaining the SBP-RRI coherence in the LF and perhaps in the HF band.