Effects of cardiac glycosides on spontaneous efferent activity in vagus and sympathetic nerves of cats

Efferent neural traffic over filaments from the cervical and thoracic vagi, and over postganglionic filaments emerging from the stellate ganglion, was studied in cats subjected to progressive, fatal intoxication with digitoxin or ouabain. Vagal efferent activity was increased by glycoside administration in 71% of trials. Depression was never observed. No specific effect on sympathetic activity was noted prior to the onset of cardiac arrhythmia. In the later stages of glycoside intoxication, however, enhancement of sympathetic activity was uniformly observed. Except as an almost terminal event, neither vagal nor sympathetic activity was consistently related to heart rate or level of systemic blood pressure. A reciprocal relationship between the two autonomic systems was not revealed.