Reduced incidence of cortical spreading depression in the course of pentylenetetrazol kindling in rats.

Subconvulsive dosages (40 mg/kg) of intraperitoneally applied pentylenetetrazol (PTZ) elicit, after a latency of 1 min, slow potential waves of spreading depression (SD) in the thalamus and 20 s later also in the cerebral cortex of rats. The PTZ-induced SD waves appear only exceptionally in the caudate nucleus and hippocampus. Repeated daily application of 40 mg/kg PTZ elicits kindling of epileptic phenomena manifested by increasing incidence of high-amplitude spikes in the EEG, myoclonic jerks and minimal and later maximal generalized seizures but by decreasing incidence of cortical SD. It is concluded that kindled epileptic activity interferes with the generation of SD waves the reduced incidence of which may contribute to the development of more severe forms of epilepsy.