Hippocampal Single-Unit Firing Patterns on an Experimental Epilepsy Model

GORI B.; GALARDI M.; GRANADO M.; BLENKMANN A.; COLLAVINI S.; BATTAGLIA G; KOCHEN SILVIA

Rio de Janeiro

Congreso; Congreso; 9th World Congress International Brain Research Organization (IBRO); 2015; 2015

International Brain Research Organization (IBRO)

Objective: Epileptic seizures are sudden changes in neural activity that interfere with the normal functioning of the neural network, expressed through hypersynchronic discharges. There are several experimental models of epilepsy. One of the most widely accepted for mesial temporal lobe epilepsy (MTLE) is Kindling. Hippocampal Rapid Kindling derives from traditional Kindling, being a more practical experimental model because it renders fully klindled animals in a shorter period of time. The aim of this study is to analyze how single-unit activity would be affected during RK-induced seizures.Methodology: Male Wistar rats were implanted with a bipolar macroelectrode in the CA1 region of right ventral hippocampus, through which they were kindled. Additionally, eight microwires were placed in the CA1 region of right dorsal hippocampus. Single-unit activity (SUA) was recorded and sorted during ictal and interictal periods of kindled seizures. SUA, electroencephalographic signals (EEG) and local field potentials (LFP) ictal activity were analyzed in ventral and dorsal right hippocampus.Results: We found heterogeneous changes in neuronal firing rate during electrographic seizure activity. Different patterns of neuronal activity was observed. Some neurons increase and others decrease their firing rates, while many units did not change. The seizure termination was mainly accompanied by a prominent decrease in neuronal firing activity of all registered neurons. Disucussion: This study found consistent results with earlier evidence. These different degrees of stereotypical firing patterns during seizures might depend on whether or not neurons are actually being recruited by the propagating wave of seizure spread. As others authors have attempted to explain in clinical studies[1,2], this shutdown of activity observed after seizure termination could possibly be caused by feedforward inhibition generated by a homogeneous activation of inhibitory neurons at a different location. Conclusion: The combined study of single-unit firing rate, EEG and LFP can provide new insights into the process of transition to seizure, allowing us to assess more precisely the dynamic changes involved in epileptogenesis. Future studies are needed to understand how this patterns would be involved in epileptogenic networks. Study funded by UBACYT, University of Buenos Aires 1-Schevon et al. Nat Commun, 2012 2-Mormann et al. Epilepsy Curr, 2013