Effects of diphenylhydantoin on cardiac arrhythmias induced by carotid occlusion in the cat.

: The effects of diphenylhydantoin (DPH) on cardiac arrhythmias induced by occlusion of the common carotid arteries were studied in vagotomized cats under light chloralose anesthesia. It was found that the mean effective dose of DPH via the i.v. route was 11.0 mg/kg. When DPH was injected into the vertebral artery, the carotid artery or the 4th cerebral ventricle, the mean effective dose was 0.8, 1.2 and 0.32 mg/kg, respectively, When DPH was injected directly into the posterior hypothalamic regions, the mean effective dose was even smaller, i.e., 0.14 mg/kg. On the other hand, when DPH was injected into the left ventricle of the heart, the mean effective dose was 1.7 mg/kg and the dose was significantly increased to 4.4 mg/kg when cerebral circulation was temporarily occluded. The data suggest that DPH exerts a potent antiarrhythmic effect through its action on the central nervous system. For the cardiac arrhythmias induced by occlusion of the common carotid arteries, it appears likely that DPH acts on the posterior hypothalamus.