Effect of Quabain and Its Interaction with Diphenylhydantoin on Cardiac Arrhythmias Induced by Hypothalamic Stimulation.
ARMED FORCES RADIOBIOLOGY RESEARCH INST BETHESDA MD
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Cardiac arrhythmias induced by central nervous system stimulation in the cat were used to evaluate the possible CNS effects of ouabain and diphenylhydantoin. Electrical stimulation of the posterior portion of the hypothalamus resulted in alterations of cardiac rhythm, and recordings from cardiac bound sympathetic nerves revealed continuous activity during the time of arrhythmia. The increased response of the heart to brain stimulation in the presence of various doses of ouabain was associated with an increased discharge of cardiac sympathetic nerves, indicating that ouabain was exerting its arrhythmogenic enhancing effect on the central nervous system rather than on the heart. Pretreatment with diphenylhydantoin prevented the arrhythmias produced by the combination of ouabain and hypothalamic stimulation. Prevention of the arrhythmia was associated with prevention of the associated sympathetic hyperactivity responsible for the arrhythmia, thus indicating a central nervous system site of action of diphenylhydantoin. These data suggest that central nervous effects of ouabain and diphenylhydantoin are important in the ability of these drugs to alter cardiac rhythm.