Convulsive activity in the electroencephalogram in rats sensitive and tolerant to pentylenetetrazol kindling

Studies on rats divided into two groups with different sensitivities on the basis of manifest convulsive activity in response to pentylenetetrazol kindling showed that both "tolerant" and "sensitive" rats showed convulsive discharges on EEG traces. However, as compared with values in "tolerant" rats, the number of convulsive discharges in "sensitive" rats was 60% greater, convulsive discharges occurred 45 sec later, and had a duration in the first 45 post-injection minutes which was 70% longer. There was no difference between the mean durations of convulsive discharges in the two groups. The EEG frequency power peak in "tolerant" rats was more marked than that in "sensitive" animals, and was located at 7.2 Hz. These data led to the conclusion that pentylenetetrazol kindling induces epileptic activity on the EEG in rats independently of whether or not the animals showed behavioral seizures, though there were significant differences in measures of this activity in "sensitive" and "tolerant" rats.