This study was designed to evaluate the blood-brain barrier permeability characteristics of the WAG/Rij strain of rats that are an ideal model for human absence epilepsy, in controls and pentylenetetrazole-induced seizures conditioned to Evans blue-albumin. For this, WAG/Rij and Wistar rats were treated with either saline or 55 mg kg(-1) pentylenetetrazole i.v. after the rats were injected with 3 mi kg(-1) of 2% Evens blue. Total duration of seizure activity and regional blood-brain barrier permeability changes were determined and compared with control Wistar rats. The duration of convulsive activity which was induced by pentylenetetrazole was significantly longer in WAG/Rij rats than in Wistar rats. The blood-brain barrier opening to Evans blue was not the case in saline-injected WAG/Rij or Wistar rats, but this was clearly seen in both strains after pentylenetetrazole-induced convulsions. EB leakage was mainly seen in the cortical areas, cerebellum, pens, thalamus, hypothalamus and corpus striatum of WAG/Rij rat brain, whereas this was recorded in the preoptic area, bulbus olfactorius, midbrain, hypothalamus, corpus striatum and inferior colliculus of the Wistar rats brain. As a result, the WAG/Rij rats were more susceptible than Wistar rats to PTZ-induced generalised tonic-clonic convulsions, and a different pattern in PTZ-induced changes in BBB permeability was observed between WAG/Rij rats and Wistar rats. (C) 1999 Academic Press.