Phosphatase inhibition prevents the activity-dependent trafficking of GABA<inf>A</inf> receptors during status epilepticus in the young animal

Suchitra Joshi, Karthik Rajasekaran, Kyle M. Hawk, Jasmit Brar, Brittany M. Ross, Christine A. Tran, Stephen J. Chester, Howard P. Goodkin

Research output: Contribution to journalArticle

12 Scopus citations

Abstract

Summary Objectives To determine if the activity-dependent trafficking of γ2 subunit-containing γ-aminobutyric acid type A receptors (GABA<inf>A</inf>Rs) that has been observed in older animals and posited to contribute to benzodiazepine pharmacoresistance during status epilepticus (SE) is age-dependent, and to evaluate whether blockade of protein phosphatases can inhibit or reverse the activity-dependent plasticity of these receptors. Methods The efficacy and potency of diazepam 0.2-10 mg/kg administered 3 or 60 min after the onset of a lithium/pilocarpine-induced seizure in postnatal day 15-16 rats was evaluated using video-electroencephalography (EEG) recordings. The surface expression of γ2 subunit-containing GABA<inf>A</inf>Rs was assessed using a biotinylation assay, and GABA<inf>A</inf>R-mediated miniature inhibitory postsynaptic currents (mIPSCs) were recorded using whole-cell patch-clamp recording techniques from dentate granule cells in hippocampal slices acutely obtained 60 min after seizure onset (SE-treated). The effect of the protein phosphatase inhibitors FK506 and okadaic acid (OA) on the surface expression of these receptors was determined in organotypic slice cultures exposed to high potassium and N-methyl-d-aspartate (NMDA) or in SE-treated slices. Results Diazepam terminated seizures of 3 min but not 60 min duration, even at the highest dose. In the SE-treated slices, the surface expression of γ2 subunit-containing GABA<inf>A</inf>Rs was reduced and the amplitude of the mIPSCs was diminished. Inhibition of protein phosphatases prevented the activity-induced reduction of the γ2 subunit-containing GABA<inf>A</inf>Rs in organotypic slice cultures. Furthermore, treatment of SE-treated slices with FK506 or OA restored the surface expression of the γ2 subunit-containing GABA<inf>A</inf>Rs and the mIPSC amplitude. Significance This study demonstrates that the plasticity of γ2 subunit-containing GABA<inf>A</inf>Rs associated with the development of benzodiazepine resistance in young and adult animals is similar. The findings of this study suggest that the mechanisms regulating the activity-dependent trafficking of GABA<inf>A</inf>Rs during SE can be targeted to develop novel adjunctive therapy for the treatment of benzodiazepine-refractory SE.

Original languageEnglish (US)
Pages (from-to)1355-1365
Number of pages11
JournalEpilepsia
Volume56
Issue number9
DOIs
StatePublished - Sep 1 2015

Keywords

  • Benzodiazepine
  • FK506
  • Okadaic acid
  • Phosphatase

ASJC Scopus subject areas

  • Clinical Neurology
  • Neurology

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    Joshi, S., Rajasekaran, K., Hawk, K. M., Brar, J., Ross, B. M., Tran, C. A., Chester, S. J., & Goodkin, H. P. (2015). Phosphatase inhibition prevents the activity-dependent trafficking of GABA<inf>A</inf> receptors during status epilepticus in the young animal. Epilepsia, 56(9), 1355-1365. https://doi.org/10.1111/epi.13098