Growth-associated phosphoprotein expression is increased in the supragranular regions of the dentate gyrus following pilocarpine-induced seizures in rats

Neuroplasticity has been investigated considering the neuronal growth-assoc iated phosphoprotein as a marker of neuronal adaptive capabilities. In the present work, studying the hippocampal reorganization observed in the epile psy model induced by pilocarpine, we carried out quantitative western blott ing associated with immunohistochemistry to determine the distribution of g rowth-associated phosphoprotein in the hippocampus of rats in acute, silent and chronic periods of this epilepsy model. The fibers and punctate elemen ts from the inner molecular layer of the dentate gyrus were strongly immuno stained in animals killed 5 h after status epilepticus, compared with the s ame region in control animals. Rats presenting partial seizures showed no a lterations in the immunostaining pattern compared with saline-treated anima ls. The hippocampal dentate gyrus of animals during the seizure-free period and presenting spontaneous recurrent seizures was also characterized by st rong growth-associated phosphoprotein immunostaining of fibers and punctate elements in the inner molecular layer, contrasting with the control group. As determined by western blotting analysis, growth-associated phosphoprote in levels increased following status epilepticus and remained elevated at t he later time-points, both during the silent period and during the period o f chronic recurring seizures. Pilocarpine-treated animals, which did not de velop status epilepticus, showed no change in growth-associated phosphoprot ein levels, indicating that status epilepticus is important to induce growt h-associated phosphoprotein overexpression. The measurement of this overexpression could represent one of the early sig nals of hippocampal reorganization due to status epilepticus-induced damage . (C) 1999 IBRO. Published by Elsevier Science Ltd.