Two Types of Epileptiform Activity Induced in Rats by Repeated Injections of Subconvulsive Picrotoxin Doses

Abstract

Seizure activity in rats was induced by picrotoxin i.p. injected every 30 min for 4 h in subconvulsive doses (0.9 mg/kg in the first and 0.7 mg/kg in subsequent injections). Such picrotoxin-evoked epileptiform activity (EA) could be divided into two types, with the development of exclusively peak-wave (P-W) complexes (68.4%) and with generation of regular cortical peaks and only separate short P-W discharges (31.6%). In animals with EA of the first type, we observed the gradual development of clonic seizures of increasing intensities. In some rats of this group after the final (ninth) injection of picrotoxin, dramatic clonico-tonic seizures were observed. In animals with EA of the second type, the duration of P-W discharges after final injections of picrotoxin was shorter than in rats without generation of cortical peaks; these discharges were accompanied by clonic seizures of smaller intensity.