CNS site of antiarrhythmic action of diphenylhydantoin (DPH) in the cat.

Diphenylhydantoin (DPH) is known to be a potent anticonvulsant agent, useful in treating and preventing grand mal seizures. More recently, DPH was reported also to be a potent antiarrhythmic agent acting by means of a depressant action on the heart. The present experiments demonstrated that DPH has also a potent antiarrhythmic action when administered to the CNS. The posterolateral hypothalamus was stimulated in cats to evoke cardiac arrhythmias of varying severity both during and after stimulation. In general, it was found that the post-stimulus arrhythmias were obtained more readily than those during stimulation. The mean effective dose of DPH required to prevent the arrhythmias via the i.v. route was 11.9 mg/kg, and that via the vertebral artery route and via the fourth ventricular route was only 1.9--1.4 and 1.4 mg/kg, respectively. These results suggest that though DPH has identifiable antiarrhythmic action on the heart itself it has a strong antiarrhythmic effect via the central nervous system as well.