Effects of digoxin on the control of heart rate and atrioventricular conduction in the dog.
The effects of digoxin on the chronotropic and dromotropic responses of the heart to autonomic neural stimulation were determined in anaesthetised, open chest dogs. Digoxin did not alter the negative chronotropic response of the heart to vagal stimulation. In contrast, digoxin reduced the positive chronotropic response to sympathetic stimulation by 40%. There was a pronounced vagal-sympathetic interaction such that the positive chronotropic response to strong sympathetic stimulation was attenuated by 72% when a near maximal vagal stimulation was delivered concurrently. However, digoxin did not alter this autonomic interaction. In addition, digoxin did not alter the positive dromotropic response evoked by the sympathetic stimulation. In contrast, digoxin potentiated the increase in A-V conduction time evoked by vagal stimulation (10 Hz) by 147%. No significant vagal-sympathetic interaction in the autonomic control of the dromotropic response was observed; ie, the responses of A-V conduction to combined sympathetic and vagal stimulation were essentially the algebraic sum of the responses to the individual stimulations. This lack of autonomic interaction in modulating A-V conduction time was not altered by digoxin, despite its potentiation of the dromotropic response to vagal stimulation.
D000818:Animals; D001283:Atrioventricular Node / Q000187:drug effects*; D004077:Digoxin / Q000494:pharmacology*; D004285:Dogs; D004558:Electric Stimulation; D006329:Heart Conduction System / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects*; D009431:Neural Conduction / Q000187:drug effects; D013268:Stimulation, Chemical; D013564:Sympathetic Nervous System / Q000187:drug effects; D014630:Vagus Nerve / Q000187:drug effects
D004077:Digoxin