Effect of Hexametonium, Atropine, Anapriline and Their Combination on the Heart Rate Variability in Rats

In this work, we set out to study changes in the heart rate frequency (HRF) and wave characteristics of the heart rate variability (HRV) of nonlinear male rats in pharmacological tests under a single administration of hexametonium (HM, 7 mg/kg), atropine (AT, 1 mg/kg), anapriline (ANP, 2 mg/kg), as well as under a sequential administration of HM and atropine (anapriline) in the same doses. A spectral analysis of the HRV was carried out across the following ranges: HF (0.9–3.5 Hz), LF (0.32–0.9 Hz), VLF (0.15–0.32 Hz). HM administration increased the HRF by 12–16%, simultaneously reducing the power of VLF, LF and HF by 85% (p<0.001), 60% (p<0.05) and almost 40%, respectively. This indicates the degree of participation of H-cholinergic transmission in the formation of HRV waves at the level of vegetative nodes. The blockade of M-cholinoreceptors (M-ChR) with AT sharply increased the HRF (by 30%, p<0.001) and reduced the wave power of the HRV spectrum by 95–98% (p<0.001), which confi rms the leading role of the cardiomyocyte M-ChR system in the formation of all the waves of the HRV spectrum. The injection of the β-AR blocker lowered the HRF by 25% (p<0.001) and the HRV wave power, in particular VLF, by 70% (p<0.01). A preliminary blockade of the vegetative nodes by HM somewhat weakened a drop in the power of HRV waves after AT administration, leveled the reduction of the HRF and potentiated the increase in the power of HF waves after ANP administration. The results indicate that the wave power across the entire range of the HRV spectrum is greatly determined (by 95–98%) by regulatory infl uences through the M-cholinoreceptors of the cardiomyocyte system, as well as by their interaction with infl uences through the myocardial adrenoreceptors and the ganglionic level of the autonomic nervous system. Vegetative nodes contribute to the formation of all HRV waves, in particular VLF and LF, change the degree and character of HRV changes when affecting the myocardial M-ChR and AR, which should be taken into account in experimental practice.