Dynamics of cardiac rhythm in the transitional period during controlled physical exercises in persons of various ages

The transitional cardiac rhythm processes of work-in and recovery under standard dynamic loads of 25 and 50 W were studied in 90 healthy people aged 20-89 and in 15 elderly people being trained for endurance. The rhythmographic method was used for that purpose. Duration of the transitional processes (work-in and recovery) was revealed to considerably increase with age, while the cardiac rhythm increment--to decrease within the first 10 seconds of the work-in period. The data obtained suggest a worsened quality of the cardiac rhythm regulation in the transitional periods during aging, that is a result of an impairment of the vegetative influences on the sinoatrial node.     

Paradoxical vagal effects on the cardiac rhythm in cats

In anaesthetised cats, an increase in the vagal burst rate resulted in a paradoxical decrease of vagal bradycardia. This seems to be due to a shift of the vagal stimulus position towards early phase of cardiac cycle. The mechanism of this paradoxical effect depends on the magnitude of vagal chronotropic effect upon the time of vagal stimulus delivery within cardiac cycle.     

Effect of prednisolone on the gastric juice basal secretion during blockade of M-cholinoreceptors by gastrozepin in rats]

A moderate depression of the stomach M-cholinic receptors was found to facilitate the prednisolone glucocorticoid stimulating effect on basal gastric secretion.     

Control of cardiac rhythm by stimulation of the vagus nerve in bursts in the rat

Burst stimulation of the vagus nerve in rats made it possible to obtain the ranges of the heart rate regulation. The increase of the number of impulses in a burst from 1 to 16 leads to a consistent decrease in the range of regulation from respectively 72.1 and 66.7% to 30.4 and 25% of the initial rate. The maximal range (10.1% of the initial rate) is reached with 4 impulses in a burst. The phenomenon of the regulation is reversed by atropine.     

Types of the peptide modulation of the vagus nerve effect on the heart rhythm

In anaesthetised cats, effects of 24 regulatory peptides upon inhibitory tonic and synchronizing components of vagal chronotropic action, were studied. The findings allowed to divide the peptidergic vagotropic activity into three types: (1) a selective action upon inhibitory tonic vagal effect; (2) a selective modulation of synchronizing vagal effect; (3) opposite changes in the vagal chronotropic effect components. The peptides seem to be able to modulate both the vagal bradycardia and the functional structure of parasympathetic chronotropic effect.     

Blood pressure regulation during cardiac autonomic blockade: effect of fitness

The purpose of this study was to determine the role of the autonomic nervous system's control of the heart in fitness-related differences in blood pressure regulation. The cardiovascular responses to progressive lower-body negative pressure (LBNP) were studied during unblocked (control) and full blockade (experimental) conditions in 10 endurance-trained (T) and 10 untrained (UT) men, aged 20-31 yr. The experimental conditions included beta 1-adrenergic blockade (metoprolol tartrate), parasympathetic blockade (atropine sulfate), or complete blockade (metoprolol and atropine). Heart rate, blood pressure, forearm blood flow, and cardiac output were measured at rest and -16 and -40 Torr LBNP. Forearm vascular resistance, peripheral vascular resistance, and stroke volume were calculated from these measurements at each stage of LBNP. Blood pressure was maintained, primarily by augmented vasoconstriction, equally in T and UT subjects during complete and atropine blockade. The fall in systolic and mean pressure from 0 to -40 Torr was greater (P less than 0.05) in the T subjects during the unblocked and metoprolol blockade conditions. This reduced blood pressure control during unblocked condition was attributable to attenuated vaso-constrictor and chronotropic responses in the T subjects. We hypothesize that an autonomic imbalance (elevated base-line parasympathetic activity) in highly trained subjects restricts reflex cardiac responses, which accompanied by an attenuated vasoconstrictor response, results in attenuated blood pressure control during a steady-state hypotensive stress.     

Effect of the sympathetic nervous system in regulating heart rhythm during burst stimulation of the vagus nerve

In cat experiments, the right inferior cardiac nerve was stimulated at a frequency of 2 and 4 Hz and the right vagus by bursts of 1, 2, 4, 8 and 16 impulses. Stimulation of the inferior cardiac nerve shifted the ranges of the heart rate control up the frequency scale. The shift of the range boundaries was mainly determined by the intensity of sympathetic regulation and by the number of impulses in a burst which stimulates the vagus nerve.     

Dynamics of heart rhythm in chimpanzees during the perception of the emotionally colored human voice

The performed study allowed to observe in two chimpanzees both common and individual changes of the heart rate under the action of human voice with emotionally positive or negative intonation, as well as under the action of preferred (sweet) or rejected (quinine solution) natural stimulus. The common property consists in a significant slowing down of the heart rate in response to negative vocal signal and rejected natural stimulus and in only slight change of the heart rate in response to positive signals. Individual properties comprise differences in reactions of the cardiovascular system of both animals to negative action: a greater efficiency of the vocal signal for one chimpanzee and of the direct (natural) stimulus for the second one.