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In cats, magnesium, potassium and finoptin diminished the vagal chronotropic effect whereas calcium potentiated it. In potassium chloride administration, the vagotropic action was due to a selective diminishing of the tonic component.
Effects of taurin, somatostatin, serotonin and noradrenaline upon the vagal chronotropic action and its components were studied in anesthetised cats. The data obtained suggests the existence of a specific transmitter link for vagal tonic and synchronizing effects upon cardiac rhythm.
In experiments on frogs, rats, rabbits, cats, dogs and simians the synchronization of cardiac and vagal rhythms was achieved during stimulation of vagus nerve. The relative bounds of the synchronization ranges were not dependent on the species of animal or level of sympathetic activity. In this connection, the whole variety of the cardiochronotropic… (More)
Dromotropic vagal effect was shown to consist of a prolonged tonic component and a short-term one depending on the interval between the burst irritation of the vagus nerve and the P-wave of the ECG.
Sympathetic nerves were shown to perform potentiation or inhibition of synchronizing or tonic components of vagal chronotropic effect. The potentiation of the synchronizing component seems to be exerted through the ansa subclavia whereas the other effects--through the caudal cardiac nerve.
Denervation of the heart (bilateral vagotomy and propranolol) in artificially ventilated cats didn't remove respiratory peaks on the spectrogram of heart rate, while burst stimulation of vagus nerve increased or decreased them several times by synchronization of the heart and vagus rhythms, which in its turn was observed under the bradycardia only. At the… (More)
The effect of met- and leu-enkephalins in cats was characterised by depressing vagotropic action due to a selective decrease in the tonic component. The potentiation of synchronizing actions may serve as an index of a reliable and stable mechanism of the beat-by-beat control of the cardiac rhythm.
It is demonstrated that sympathetic nerves may strengthen or depress the synchronizing or tonic components of vagal chronotropic effect, but the former was absent if extracardiac nerves were cut bilaterally.
Burst vagus stimulation led to synchronization of the cardiac and vagal rhythms at certain frequency ranges. The increase of the number of impulses in a burst from 1 to 16 extended the range of synchronization and shifted it towards lower frequencies forming a total range of exact regulation of the heart rate within 85--40% of the initial rate. It was… (More)