Chronodromotropic coordination in cats

Abstract

The coordinated nervous influences on HR and atrioventricular conduction velocity (chronodromotropic coordination) were examined in wakeful cats. The wave structure and reflex reactions of RR and atrioventricular (AV) intervals to stress noise stimulation were studied under normal conditions and during the action of blockers of peripheral receptors in ANS. Variations of both intervals had similar wave structure (power spectrum) and similar reactions to noise stimulus. Atropine pronouncedly decreased all components of the spectra in the high, low, and very low frequency ranges. It eliminated the reactions of both intervals to noise stimulation. In RR intervals, the high-frequency spectrum component decreased more strongly than the low-frequency ones. By contrast, in AV intervals atropine most greatly decreased the very-low-spectrum component, while the high frequency was decreased less of all. Propranolol produced no effect on the response to noise. It did not decrease components of the wave structure in both intervals, except for the very-low-frequency peak of AV interval. The nervous chronotropic and dromotropic influences were largely coordinated, although they were not obligatorily parallel.

Effect of pentobarbital on spectral characteristics and phase ratios of wave oscillations of cardiac contraction period and time of atrioventricular conduction in cats

“…We found that pentobarbital had a similar effect on AV interval, causing its shortening and decrease in the ranges of all frequency bands. This, together with other data [1,2], indicates a close relationship between chronotropic and dromotropic nervous effects (chronodromotropic coordination). However, it does not mean that AV delay always changes strictly parallel to the period of cardiac contractions.…”

“…However, it does not mean that AV delay always changes strictly parallel to the period of cardiac contractions. It was previously shown that the same reflexogenic exposure can cause opposite reactions of RR and AV intervals [1] and that blockers of the autonomic nervous system peripheral receptors have different effects on the spectral characteristics of RR and AV intervals [2]. One more manifestation of the intricate chronodromotropic coordination is presumably the inversion of phase ratio of respiratory oscillations of RR and AV intervals detected in this study.…”

“…Spectral analysis was carried out using fast Fourier transform with preliminary deduction of the mean, elimination of the trend, and using Hamming window (5 points wide). The entire spectrum of frequencies was divided into high-frequency, low-frequency, and very-low-frequency bands (0.22-1.20, 0.04-0.22, and <0.04 Hz, respectively [2]). Absolute density of spectral power was calculated for each band, denoted, in accordance with universal abbreviations, as HF for high frequency band, LF for low frequency band, and VLF for very low frequency band.…”

“…Similar wave oscillations of atrioventricular (AV) interval were detected [2,9,10,12], spectral analysis thereof was carried out, transmitter nature was investigated, and ratio between the wave structure of AV interval and cardiac contractions period (RR interval) was studied in cats [2]. Here we studied the effect of barbiturate narcosis, one of the most prevalent methods of anesthesia in physiological experiments, on the wave structure of AV interval and its ratio with the RR interval wave structure.…”

Chronotropic and dromotropic components of cardiac reflexes in the cat

“…At the same time, dromotropic, inotropic, and lusitropic effects are poorly studied. The ratio between various components of cardiac reflexes was estimated only in few studies [1][2][3][4].Here we evaluated the ratio between chronotropic and dromotropic components of various cardiac reflexes in cats. …”