Kir4.1 RNA Interference by in Utero Electroporation Fails to Affect Ictogenesis and Reveals a Possible Role of Kir4.1 in Corticogenesis

Astrocyte dysfunction, and in particular impaired extracellular potassium spatial buffering, has been postulated to have a potential role in seizure susceptibility and ictogenesis. Inwardly rectifying potassium (Kir) channels, and specifically KIR4.1, have a predominant role in K+ homeostasis and their involvement in neuronal excitability control have been hypothesized. To avoid the severe side effects observed in Kir4.1 cKO, we studied the effects of Kir4.1 down-regulation in cortical astrocytes by using Kir4.1 RNA interference (RNAi) technique combined with in utero electroporation (IUE) at E16 and a piggyBac transposon system. Kir4.1 down-regulation was confirmed by immunohistochemistry and field fraction analysis. To investigate if Kir4.1 silencing affects 4AP-induced seizure threshold and extracellular potassium homeostasis, simultaneous in vitro field potential and extracellular K+ recordings were performed on somatosensory cortex slices obtained from rats electropo-rated with a piggyBac-Kir4.1-shRNA (Kir4.1(-)) and scrambled shRNA (Kir4.1(Sc)). Electrophysiological data revealed no significant differences in terms of seizure onset and seizure-induced extracellular K+ changes between Kir4.1(-) and Kir4.1(Sc) rats. Intriguingly, immunohistochemical analysis performed on slices studied with electrophysiology revealed a reduced number of neurons generated from radial glial cells in Kir4.1(-) rats. We conclude that focal down-regulation of Kir4.1 channel in cortical astrocytes by Kir4.1 RNAi technique combined with IUE is not effec-tive in altering potassium homeostasis and seizure susceptibility. This technique revealed a possible role of Kir4.1 during corticogenesis. (C) 2020 IBRO. Published by Elsevier Ltd. All rights reserved.