Increased GABA_A‐Receptor α1‐Subunit Expression in Hippocampal Dentate Gyrus after Early‐life Status Epilepticus

Abstract

Summary:Purpose: Previous studies in neonatal (postnatal day 10) and adult rats suggest that status epilepticus (SE) induces changes in the α1 subunit of the GABA A receptor (GABRA1) in dentate granule neurons (DGNs) that are age dependent and vary inversely with the likelihood of epilepsy development. In the present study, we examined GABRA1 expression after SE at postnatal day 20 (P20), an intermediate age when only a subset of SE-exposed animals develop epilepsy.Methods: SE was induced with lithium-pilocarpine or kainate at P20. Animals were video-EEG monitored after SE to determine the presence or absence of spontaneous seizures. GABRA1 mRNA and protein levels were determined 7 days or 3 months later in SE-exposed and control animals by using a combination of aRNA amplification, Western blotting, and immunohistochemistry techniques.Results: GABRA1 mRNA levels in DGNs of SE-exposed rats that did not become epileptic were higher than those in control rats, but were not different from DGNs in epileptic SE-exposed rats. GABRA1 protein levels in dentate gyrus were significantly increased in both epileptic and nonepileptic SE-exposed rats compared with controls. GABRA1 mRNA changes were region specific and did not occur in CA1 or CA3 areas of hippocampus. GABRA1 alterations were present by 1 week after P20 SE and were similar whether pilocarpine or kainate was used to induced SE.Conclusions: P20 SE results in persistent increases in GABRA1 levels selectively in dentate gyrus. These changes preceded the onset of epilepsy, were not model specific, and occurred in both epileptic and nonepileptic animals.

Enhancing GABAAReceptor α1 Subunit Levels in Hippocampal Dentate Gyrus Inhibits Epilepsy Development in an Animal Model of Temporal Lobe Epilepsy

“…The cRNA was purified using the RNeasy MinElute Cleanup kit protocol (Qiagen, Valencia, CA) according to the protocol of the manufacturer. [P 32 ]dCTP was incorporated into the radiolabeled cDNA probe using SuperScript II RNase HϪ reverse transcriptase and hybridized for 18 h against a slot blot containing GABR cDNAs (␣1-␣6, ␤1-␤3, ␥1-␥3, ␦, , , ) using published protocols and conditions (Raol et al, 2006).…”

“…Dissection of DG and RNA isolation were performed using standard procedures as described previously (Roberts et al, 2005;Raol et al, 2006). T7-(dT) 24 primer and SuperScript II RNase HϪ reverse transcriptase were used for cDNA synthesis, and the AmpliScribe T7 High Yield Transcription kit (Epicenter Technologies, Madison, WI) was used for RNA amplification according to published methods (Raol et al, 2006).…”

The Brain, Seizures and Epilepsy Throughout Life: Understanding a Moving Target

“…Neonatal seizures may directly influence the effects of activation of GABA-A receptors (74-77) and alter receptor expression at both excitatory and inhibitory synapses. For example, such seizures modify the expression of glutamate receptors of various types (78-81), GABA receptors (82), and a number of additional important ion channels (83)(84)(85)(86). Notably, both the structural and molecular changes provoked by neonatal seizures might be persistent (87,88).…”

Expression of GABAA receptor α1 subunit mRNA and protein in rat neocortex following photothrombotic infarction

“…GABA A Rs are well studied in models of temporal lobe epilepsy (Rice et al, 1996;Sperk et al, 2004). Interestingly, Raol et al (2006b) showed that an increased level of GABA A R α 1 subunits in the dentate gyrus can affect the development of spontaneous seizures after status epilepticus. In addition, recent studies have identified the α 1 (A294D) and α 1 (A322D) genetic mutations of the GABA A R α 1 subunit that are associated with juvenile myoclonic epilepsy (Cossette et al, 2002;Gallagher et al, 2004;Mizielinska et al, 2006).…”