The blood-brain barrier lesion and the systemic convulsant model of epilepsy

Systemic kainic acid (KA) at 1 mg/kg crosses the normal blood-brain barrier (BBB) of rats to produce scattered sharp waves for ~10 min on the EEG, but is without observable effect, producing no EEG or behavioral changes, at 0.5 mg/kg. When the BBB is opened in most of one hemisphere by 6,000 rads, the rats are clinically normal and have a normal EEG. When the irradiated rats are challenged with 0.5 mg/kg KA, intense, highly lateralized epileptiform bursts result; these bursts last 1-10 s and recur for 90 mins. This phenomenon is repeatable for the 1 week that the BBB is open. The results are identical when the BBB is opened with a pin lesion. Because endogenous glutamate agonists are common, these data suggest a possible pathophysiologic mechanism for human epilepsy.