Kainic acid increases the proliferation of granule cell progenitors in the dentate gyrus of the adult rat.

Granule cell progenitors in the dentate gyrus of the hippocampal formation have the unusual capacity to be able to divide in the brains of adult rats and primates. The basal proliferation rate of granule cell progenitors in the adult rat is low compared with development, however, it is possible that this rate may become significantly altered under pathological conditions such as epilepsy. We have investigated whether the proliferation of granule cell progenitors is increased in adult rats in a model of temporal lobe epilepsy, by using systemic bromodeoxyuridine injections to label dividing cells. We report here for the first time that granule cell neurogenesis is increased bilaterally 1 week after a single unilateral intracerebroventricular injection of kainic acid. Bromodeoxyuridine labeled neurons increased at least 6-fold on the side ipsilateral to the kainic acid injection compared to controls, but significantly, were also increased, by at least 3-fold on the side contralateral to the injection. The dividing cells in the subgranular zone were identified as neurons since they expressed Class III beta tubulin but not glial fibrillary acidic protein.