Preparation of Acute Human Hippocampal Slices for Electrophysiological Recordings

Abstract

Epilepsy affects about 1% of the world population and leads to a severe decrease in quality of life due to ongoing seizures as well as high risk for sudden death. Despite an abundance of available treatment options, about 30% of patients are drug-resistant. Several novel therapeutics have been developed using animal models, though the rate of drug-resistant patients remains unaltered. One of probable reasons is the lack of translation between rodent models and humans, such as a weak representation of human pharmacoresistance in animal models. Resected human brain tissue as a preclinical evaluation tool has the advantage to bridge this translational gap. Described here is a method for high quality preparation of human hippocampal brain slices and subsequent stable induction of epileptiform activity. The protocol describes the induction of burst activity during application of 8 mM KCl and 4-aminopyridin. This activity is sensitive to established AED lacosamide or novel antiepileptic candidates, such as dimethylethanolamine (DMEA). In addition, the method describes induction of seizure-like events in CA1 of human hippocampal brain slices by reduction of extracellular Mg 2+ and application of bicuculline, a GABA A receptor blocker. The experimental set-up can be used to screen potential antiepileptic substances for their effects on epileptiform activity. Furthermore, mechanisms of action postulated for specific compounds can be validated using this approach in human tissue (e.g., using patch-clamp recordings). To conclude, investigation of vital human brain tissue ex vivo (here, resected hippocampus from patients suffering from temporal lobe epilepsy) will improve the current knowledge of physiological and pathological mechanisms in the human brain.

Spatiotemporal Correlation of Epileptiform Activity and Gene Expression in vitro

“…In human slices, c-FOS expression correlated with epileptiform activity, but we did not find increased expression in the onset zone, most likely due a high variability of the SLE onset and consequently probable imprecise definition. This onset variability as compared to rat tissue is likely due to the overall variability of human tissue obtained from different patients with consequent impact on the activity in vitro (Andersson et al, 2016;Wickham et al, 2018;Kraus et al, 2019) and also due to differences in tissue or different slicing angles (Kraus et al, 2020). All these variables not only influence neuronal survival and network excitability, but also could have affected gene expression.…”

In vitro and in vivo anti‐epileptic efficacy of eslicarbazepine acetate in a mouse model of KCNQ2‐related self‐limited epilepsy

“…SPW‐R activity was recorded from CA1 pyramidal layer of ventral hippocampal slices perfused with prewarmed (~35 ± 0.5°C) and carbogenated aCSF (Kubota et al, 2003; Maier et al, 2003, 2009; Papatheodoropoulos & Kostopoulos, 2002). The recordings were performed in a modified submerged‐type recording chamber with high flow rate (10 ml·min −1 ) (Hill & Greenfield, 2011; Kraus et al, 2020). The signal was sampled at 20 kHz, low‐pass filtered at 2 kHz, and digitized by a Digidata1550 interface and processed by PClamp10 software (Molecular Devices, Sunnyvale, CA, USA, ).…”

“…SPW-R activity was recorded from CA1 pyramidal layer of ventral hippocampal slices perfused with prewarmed ($35 ± 0.5 C) and carbogenated aCSF (Kubota et al, 2003;Maier et al, 2003Maier et al, , 2009Papatheodoropoulos & Kostopoulos, 2002). The recordings were performed in a modified submerged-type recording chamber with high flow rate (10 mlÁmin À1 ) (Hill & Greenfield, 2011;Kraus et al, 2020).…”