Abstracts

Rationale: Neonatal seizures (NS) are the most common form of seizures during childhood, and are refractory to conventional anti-convulsants currently used in > 50% of cases. We have previously reported that early enhancement of protein kinase activity and enhanced phosphorylation of the AMPA subtype of ionotrophic glutamate receptors, esp. GluR1 S831 and S845 play a critical role in mediating hyperexcitability following NS. Furthermore, pharmacological intervention leading to attenuation of these changes reduced epileptogenesis and post-seizure hyperexcitability after hypoxia induced seizures (J Neurosci. 2008 Aug 6; 28(32):7979-90). Here we hypothesize that transgenic knockin mice with deficits in GluR1 S831 and S845 phosphorylation may exhibit reduced seizure susceptibility and epileptogenesis in the neonatal period and provide mechanistic clues about signaling involved in epileptogenesis. Methods: GluR1 phosphomutant mice (GluR1 DPM -/-) and their wild-type siblings (GluR1 DPM +/+) were obtained by mating heterozygous mice as described previously (Cell. 2003 Mar 7; 112(5):631-43.). During the neonatal period, seizures were induced in the GluR1 DPM -/- mice and their wild-type siblings at post-natal day (P) 7 by injection of PTZ (50mg/kg i.p.). Seizures were recorded and latency to behavioral seizures recorded on a graded seizure scale. Hippocampal slices obtained from the GluR1 DPM -/- mice and their wild-type siblings at P7 and subjected to hypoxic conditions, single cell patch clamp recordings were made as described previously ( J Neurosci. 2005 Mar 30;25(13):3442-51.) Results: Transgenic knock-in mice (GluR1 DPM -/-), exhibit an increased latency to onset of first behavioral seizure following PTZ injection (6.54 min ± 0.75, p <0.005, n=23) as compared to wild-type littermates subjected to same conditions (3.75 min ± 0.39). A significant difference was observed in the survival plot between the GluR1 DPM -/- and their wild-type siblings in the latency to first behavioral seizure (p<0.001). Furthermore, hippocampal slices from wild type mice subjected to hypoxic conditions exhibit epileptiform spike bursts on patch-clamp recordings; hippocampal slices from GluR1 DPM -/- transgenic mice have an absence of induction of these epileptiform discharges. Hippocampal slices from GluR1 DPM -/- transgenic mice show a decrease in sEPSC spike frequency (60.5 ± 27%, p<0.05, n=5) in response to hypoxic conditions; in contrast GluR1 DPM +/+ wild-type mice show an increase in the action potential firing frequency (143 ± 23%, p<0.05, n =5) in response to hypoxic conditions.