Related Experiment Video
Updated: Oct 1, 2026
Recording and Modulation of Epileptiform Activity in Rodent Brain Slices Coupled to Microelectrode Arrays
Published on: May 15, 2018
Excitatory and inhibitory control of epileptiform discharges in combined hippocampal/entorhinal cortical slices
L Menendez de la Prida1, M A Pozo
1Brain Mapping Unit, Instituto Pluridisciplinar, Universidad Complutense de Madrid, Paseo Juan XXIII 1, 28040, Madrid, Spain. liset@pluri.ucm.es
Insights
Mild reduction of GABA(A) receptor inhibition induces epileptiform activity in rat brain slices. Non-NMDA receptor excitation controls these discharges, allowing for their isolation in specific brain regions.
Area of Science:
- Neuroscience
- Epilepsy Research
- Pharmacology
Background:
- Epileptiform activity is associated with imbalances in neuronal inhibition and excitation.
- Understanding regional differences in susceptibility to epileptiform discharges is crucial for epilepsy research.
Purpose of the Study:
- To investigate the induction and prevention of epileptiform activity in hippocampal/entorhinal cortical slices.
- To determine the roles of GABA(A) receptor inhibition and non-NMDA receptor excitation in generating these discharges.
- To explore regional sensitivities within the CA1, subiculum (SUB), and medial entorhinal cortex (MEC).
Main Methods:
- Utilized combined hippocampal/entorhinal cortical slices from juvenile rats (P15-21).
- Employed receptor antagonists bicuculline (GABA(A)) and CNQX (non-NMDA) to modulate neuronal activity.
- Performed extracellular and intracellular recordings to analyze epileptiform discharges upon stimulation.
Main Results:
- Low concentrations of bicuculline (<3.5 microM) induced stereotyped epileptiform discharges in CA1, SUB, and MEC.
- CA1 and SUB regions showed higher susceptibility to discharge generation than MEC.
- CNQX blocked discharges concentration-dependently, indicating critical non-NMDA excitatory control.
- CA1 region exhibited lower sensitivity to CNQX compared to SUB and MEC.
Conclusions:
- Mild reduction in GABA(A) receptor-mediated inhibition is sufficient to induce epileptiform activity.
- Non-NMDA receptor-mediated excitation plays a key role in controlling and preventing these discharges.
- Regional differences in receptor sensitivity allow for the pharmacological isolation of epileptiform activity within the CA1 region of the hippocampal-entorhinal circuitry.
Abstract:
We examined whether epileptiform activity can be induced and prevented by mild reduction of GABA(A) receptor-mediated inhibition and non-NMDA receptor-mediated excitation, respectively, in different regions of combined hippocampal/entorhinal cortical slices from juvenile rats (P15-21). We used the receptor antagonists bicuculline (GABA(A)) and CNQX (non-NMDA) as tools to investigate the sensitivities of the CA1, the subiculum (SUB) and the medial entorhinal cortex (MEC) for generating epileptiform discharges upon extracellular stimulation. We found that low concentrations of bicuculline (<3.5 microM) were enough to induce epileptiform discharges in the three regions. These discharges were similar to those observed under high concentrations of bicuculline (>10 microM) and consisted of stereotyped population bursts, recorded both extra- and intracellularly. Interestingly, the CA1 and SUB were more susceptible to generate discharges compared to the MEC in the same slices. We also found that non-NMDA excitation was critical in controlling discharges, as they were blocked by CNQX in a concentration-dependent manner. The sensitivity of the CA1 region to CNQX was lower than that of the SUB and MEC. Based on these regional differences, we show that epileptiform activity can be pharmacologically isolated within the CA1 region in the hippocampal-entorhinal circuitry in vitro.
