Susceptibility to electroshock-induced seizures in rats following neocortical injuries at different developmental stages

Brains injured at different developmental stages may acquire different susceptibility to epileptiform activities. Epileptogenesis appears to be triggered by age-dependent reactive processes including gliosis and formation of aberrant axonal connections in the tissue surrounding the lesion site. The present study focuses on relations between brain injuries at different developmental stages and subsequent susceptibility to seizures in adulthood. In 6- and 30-day-old Wistar rats (P6s and P30s, respectively), a mechanical injury was performed in the left cerebral hemisphere. From the postnatal day 60, the injured rats and non-injured controls underwent 21 daily electrical stimulations to evoke seizures. Tonic and clonic reactivity to electric stimulation in P6s and P30s showed considerably different profiles contrasting with those previously observed following pilocarpine or kainic acid administration in the same experimental paradigm. In P6s intensity of tonic seizures was significantly higher than that in controls or in P30s while clonic seizured revealed no intergroup difference. The results proved that the observed phenomena depended on the model used for experimental exploration of the problem but their structural determinants remain obscure.