Remodeling dendritic spines in the rat pilocarpine model of temporal lobe epilepsy

Dendritic degeneration is a common pathology in temporal lobe epilepsy and its animal models. However, little is known when and how the degeneration occurs. In the present study of the rat pilocarpine model, visualization of dendrites of the hippocampal dentate granule cells (DGCs) by biocytin revealed a generalized spine loss immediately after the acute seizure induced by pilocarpine. However, this generalized damage was followed by recovery and plastic changes in spine shape and density, which occurred 15-35 days after the initial acute seizure, i.e., during the period of establishing a chronic phase of this model with the induction of spontaneous seizures. The present finding suggests that initial acute seizures do not cause permanent damages in dendrites and spines of DGCs; instead, dendritic spines are dynamically maintained in the course of the establishment and maintenance of spontaneous seizures. Local dendritic spine degeneration, detected later in the chronic phase of epilepsy, is likely to have a separate cause from initial acute insults.