Heart rate variability in male rats

Abstract

The cardiovascular system is primarily controlled by the autonomic nervous system, and any changes in sympathetic or parasympathetic activity also have an impact on myocardial activity. Heart rate variability (HRV) is a readily available metric used to assess heart rate control by the autonomic nervous system. HRV can provide information about neural (parasympathetic, sympathetic, reflex) and humoral (hormones, thermoregulation) control of myocardial activity. Because there are no relevant reference values for HRV parameters in rats in the scientific literature, all experimental results are only interpreted on the basis of changes from currently measured control or baseline HRV values, which are, however, significantly different in individual studies. Considering the significant variability of published HRV data, the present study focused primarily on comparing control or baseline HRV values under different conditions in in vivo experiments involving rats. The aim of the study was therefore to assess whether there are differences in the starting values before the experiment itself.

Keywords: heart rate variability; in vivo experiments; rats.

FIGURE 1

Mean ± SD values of individual frequency HRV parameters from conscious male rats (sham and control). VLF, very low frequency of HRV (VLF‐sham n = 6; VLF‐control n = 8) LF, low frequency of HRV (LF‐sham n = 34; LF‐control n = 18); HF, high frequency of HRV (HF‐sham n = 36; HF‐control n = 19); TSP, total spectral power of HRV (TSP‐sham n = 12; TPS‐control n = 8).

FIGURE 2

Mean ± SD values of LFnu and HFnu conscious male rats (sham vs. control). LFnu (LFnu‐sham n = 26; LFnu‐control n = 4) and HFnu (HFnu‐sham n = 24; HFnu‐control n = 4)—normalized units represent the relative value of the HF and LF components of HRV in relation to TSP (after subtracting VLF power).

FIGURE 3

Averaged values of SDNN and rMSSD from conscious male rats (sham and control). SDNN (ms) (SDNN‐sham n = 11; SDNN‐control n = 25)—a frequently used index of total HRV identical to TSP. rMSSD (ms) (rMSSD‐sham n = 7; rMSSD‐control n = 23)—higher rMSSD values indicate greater parasympathetic activity.