Abstracts

Rationale: The GABA A receptor (GABAR) mediates fast synaptic inhibition in brain and changes in GABAR subunit composition have been suggested to play an important role in the development of epilepsy. Long-term alterations in GABAR subunit levels occur following status-epilepticus (SE) in adult animal models and human temporal lobe epilepsy (TLE). Viral delivery of GABAR α1 subunit into DG protects rats from development of spontaneous seizures following pilocarpine-induced SE, suggesting that α1 down-regulation may be a critical determinant of epileptogenesis. However, the mechanism of α1 subunit regulation is not completely understood. Our previous work suggests that phosphorylated cAMP response element binding protein (pCREB) and its related family member inducible cAMP early repressor (ICER) increase after SE and are mediators of α1 decreases. Further, in vitro studies show that brain derived neurotrophic factor (BDNF) induces increases in ICER and decreases in α1 subunit levels and these changes are blocked by P6, a JAK/STAT pathway inhibitor. However, an in vivo correlation between activity of the JAK/STAT pathway and ICER regulation of α1 changes is lacking. In the current study, we examined the role of JAK/STAT pathway in regulating ICER repression of α1 in an animal model of TLE. Methods: We examined the role of JAK/STAT pathway inhibition on pSTAT3 and ICER increases, and α1 decreases in microdissected dentate gyrus after SE. Results: In vivo examination of the JAK/STAT pathway reveals increases in pSTAT3 levels after SE occur from 1-48 hrs. Inhibition of the JAK/STAT pathway in vivo via P6 infusion into the hippocampus blocks the increases in both pSTAT3 and ICER levels at 48 hrs after SE and importantly, also blocks decreases in α1 mRNA at 9 days after SE. Also, chromatin immunoprecipitation studies show that following SE, pSTAT3 binds to a STAT site in the ICER promoter. Ongoing experiments are examining video and EEG monitoring of epileptic rats to determine whether blockade of α1 decreases also results in inhibition of the development of spontaneous seizures. Conclusions: Our study indicates that regulation of α1 by ICER may be mediated by the JAK/STAT pathway. Also, these findings enhance understanding of GABRA1 regulation and the mechanisms that result in the development of TLE after SE.