Effect of diphenylhydantion on cortical epileptogenic foci in the rat.

In acute experiments we studied the effect of diphenylhydantoin (DPH, 60 mg/kg i.p.) on the activity of cortical penicillin foci in 81 male rats. DPH reduced the discharge frequencies (measured by means of histograms of the intervals between adjacent discharges) and limited the projection of the discharges into non-primary cortical areas. The results for the administration of DPH before formation and after stabilization of the focus were qualitatively the same. DPH statistically significantly slowed down synchronization of the activity of two symmetrical cortical foci, but did not affect the progress of the synchronization of two asymmetrical foci, which was also very slow in the controls. DPH did not inhibit the possibility of triggering focal discharges by peripheral nerve stimulation. A detailed evaluation of focal activity allows the anti-epileptic effect of DPH to be demonstrated even in a model as potent as the penicillin focus in animals without general anaesthesia.