The effects of age on seizure susceptibility in WAG/Rij and Wistar rats

Susceptibility to PTZ-induced seizures during postnatal ontogeny (PN 10 to PN 220) was investigated in two rat strains. The WAG/Rij strain, genetically prone to developing generalised absence epilepsy and Wistar rats were tested and compared at postnatal (PN) day 10, 26, 30, 70, 90, 125 and 220 for PTZ convulsive threshold. A sub-convulsive dose of 25 mg/kg PTZ was administered every 15 min and the occurrence of clonic and tonic-clonic seizures was scored. The highest threshold of PTZ convulsions was observed at PN 30 in both strains, from that age onwards the seizure threshold significantly decreased and reached a minimum at PN 220. Between strain comparisons showed that pups and adult WAG/Rij rats have a lower seizure threshold than Wistar rats. The data indicate that changes in susceptibility tend to monotonically increase with age and that genetically prone non-convulsive WAG/Rij rats are more vulnerable to convulsive types of epilepsy than Wistar rats.