Time course of mossy fiber sprouting following bilateral transection of the fimbria/fornix.

Abstract

Lesions of the fimbria/fornix (FF) lead to a variety of epileptiform changes in hippocampal activity. In epilepsy, as well as in several experimental preparations of epilepsy, aberrant sprouting of the dentate gyrus mossy fibers (MF) is observed and has been hypothesized to play a critical role in the generation of seizure activity. We therefore sought to determine whether MF sprouting also follows FF transections. FF transections did indeed lead to MF sprouting, which became apparent at 14 days and reached asymptotic levels at 28 days post-lesion. These results indicate a possible mechanism for the epileptiform activity seen following FF lesions and provide an additional example of the diverse epileptogenic treatments that are accompanied by MF sprouting.