[Peripheral mechanisms of vagal sinus arrhythmia: a role of typical affiliation of cardiac M-cholinoreceptors].
Salvo impulses on the vagus nerve of a cat with a varying in each cardiocycle interval after ECG P wave led to recurrent variations of ECG interval P-P manifesting as sinus arrhythmia. A chronotropic effect of the vagus nerve experienced moderate changes in dislocation of the vagus stimulus position in the beginning of cardiocycle lasting about 200 ms after ECG P wave and in ECG segment T-P. Distinct (in the range 100-300 ms) variations of the interval ECG P-P lengthening took place in the change of the vagus stimulus generation moment in the narrow zone of cardiocycle of 40-70 ms duration. The zone location corresponded to the end of ECG T wave. Metoctramine or gallamine block of M2-cholinoreceptors reduced maximal lengthening of the interval P-P and severity of cycle changes of P-P interval in arrhythmia and its variation amplitude under changing moment of vagus stimulus generation in the zone of cardiocycle showing marked shifts of a chronotropic effect. M1-cholinoreceptor block with pirenzepin or receptors of M3-subtype in the action of 4-DAMP produced an opposite effect enhancing these parameters.
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D000818:Animals; D001146:Arrhythmia, Sinus / Q000209:etiology / Q000378:metabolism*; D002415:Cats; D004195:Disease Models, Animal; D004558:Electric Stimulation; D004562:Electrocardiography; D006321:Heart / Q000187:drug effects / Q000294:innervation*; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009206:Myocardium / Q000378:metabolism*; D011976:Receptors, Muscarinic / Q000378:metabolism*; D014630:Vagus Nerve / Q000502:physiology*
D018727:Muscarinic Antagonists; D011976:Receptors, Muscarinic