Alterations in the Properties of the Rat Hippocampus Glutamatergic System in the Lithium-Pilocarpine Model of Temporal Lobe Epilepsy

Status epilepticus (SE) triggers many not yet fully understood pathological changes in the nervous system that can lead to the development of epilepsy. In this work, we studied the effects of SE on the properties of excitatory glutamatergic transmission in the hippocampus in the lithium-pilocarpine model of temporal lobe epilepsy in rats. The studies were performed 1 day (acute phase), 3 and 7 days (latent phase), and 30 to 80 days (chronic phase) after SE. According to RT-qPCR data, expression of the genes coding for the AMPA receptor subunits GluA1 and GluA2 was downregulated in the latent phase, which may lead to the increased proportion of calcium-permeable AMPA receptors that play an essential role in the pathogenesis of many CNS diseases. The efficiency of excitatory synaptic neurotransmission in acute brain slices was decreased in all phases of the model, as determined by recording field responses in the CA1 region of the hippocampus in response to the stimulation of Schaffer collaterals by electric current of different strengths. However, the frequency of spontaneous excitatory postsynaptic potentials increased in the chronic phase, indicating an increased background activity of the glutamatergic system in epilepsy. This was also evidenced by a decrease in the threshold current causing hindlimb extension in the maximal electroshock seizure threshold test in rats with temporal lobe epilepsy compared to the control animals. The results suggest a series of functional changes in the properties of glutamatergic system associated with the epilepsy development and can be used to develop the antiepileptogenic therapy.