Functional changes in the septal GABAergic system of animals with a model of temporal lobe epilepsy.

The septal GABAergic system plays a central role in the regulation of activity and excitability of the hippocampus (the main locus of temporal lobe epilepsy, TLE), but the character of changes the septum undergoes in this pathology remains unknown. To address this issue we studied the influences on GABAergic receptors in septal slices from the brain of epileptic guinea pigs compared to a control. In the epileptic brain, the overall increase in the mean frequency of neuronal discharges and the rise in the number of bursting neurons were revealed. The inhibitory action of exogenously applied GABA on neuronal activity is sharply enhanced, whereas the efficacy of action of GABA(A) and GABA(B) receptor blockers decreases, indicating the alteration of intraseptal inhibitory processes in epilepsy. In epilepsy, GABA sharply increases the oscillatory activity of the part of pacemakers, and the opposite effect was observed in the control. In epileptic animals, the GABA receptor blockers did not affect burst neurons, indicating the disturbance of the tonic GABAergic control of the oscillatory activity. Thus, we demonstrated for the first time that the activity of septal neurons and their reactions to GABAergic substances in animals with TLE model changed sharply compared to healthy ones.