Power spectrum analysis of heart-rate variability in the young zucker rat

Cardiac autonomic control was studied in a group of five young hyperinsulinaemic, insulin resistant, Zucker fatty rats (ZFR) compared with a control group of five young Zucker lean rats (ZLR). Power spectrum analysis (PSA) of heart rate variability (HRV) was performed with autoregressive (AR) models. All rats were anaesthetised with sodium pentobarbital. Mean insulinaemia and glycaemia levels were 185+27 muU/ml and 159+38 mg/dl, respectively, in the ZFR, and reduced to 13+13 muU/ml (p<0.05) and 101+15 mg/dl (p<0.05), respectively, in the ZLR. No significant difference in basal blood pressure was found between the two groups. Analysis of power spectrum density, normalized by the total area, showed a marked reduction (p<0.05) in the peak amplitude of the high frequency (HF) component in the ZFR group. No significant difference was observed in the peak amplitude of low frequency (LF) component between the two strains. LF/HF ratio was higher (p<0.05) in the ZFR group. These results indicate that in the young ZFR, hyperinulinemia associates with altered sympathovagal balance in the autonomic cardiovascular control, before the onset of significant changes in both sympathetic nervous activity and blood pressure.