Chronodromotropic coordination in cats

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-spectrurn 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.