Alterations in mRNA expression of glutamate receptor subunits and excitatory amino acid transporters following pilocarpine-induced seizures in rats

Temporal lobe epilepsy is the most prevalent form of complex partial seizure, and it is frequently triggered by an initial brain-damaging insult. The prevention of epileptogenesis after a primary event could be a key innovative approach to epilepsy treatment. Therefore, it is critical to understand the pathogenic mechanisms of this process in detail. Multiple mechanisms are involved in epileptogenesis, including alterations in the expression of synaptic receptors and transporters. The present study aimed to investigate the mRNA expression of excitatory amino acid transporters 1-3 (EAATs) and the subunits of the NMDA (GluN1, GluN2a, and GluN2b) and AMPA (GluA1 and GluA2) glutamate receptors following status epilepticus in a rat lithium-pilocarpine model. The analysis of the mRNA was performed via qRT-PCR one week after pilocarpine injections (the period of epileptogenesis) into the ventral and dorsal hippocampus and the entorhinal, temporal, and medial prefrontal cortexes - brain areas that are differentially involved in the pathogenesis of TLE. We found that increased EAAT2 mRNA levels in the medial prefrontal cortex and dorsal hippocampus may represent compensatory neuroprotective changes. Alterations in the gene expression levels of AMPA receptor subunits were found in the ventral hippocampus and temporal cortex. The reduced expression of the GluN2a subunit was observed in the temporal and entorhinal cortical areas and the ventral hippocampus, which may result in the predominance of GluN2b-containing NMDA receptors in these areas. The receptors with this altered subunit composition may be involved in pathophysiological mechanisms related to epileptogenesis. These data provide a better understanding of the pathogenesis of epilepsy.