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AMPA/kainate receptor-mediated downregulation of GABAergic synaptic transmission by calcineurin after seizures in the developing rat brain.

Abstract
Hypoxia is the most common cause of perinatal seizures and can be refractory to conventional anticonvulsant drugs, suggesting an age-specific form of epileptogenesis. A model of hypoxia-induced seizures in immature rats reveals that seizures result in immediate activation of the phosphatase calcineurin (CaN) in area CA1 of hippocampus. After seizures, CA1 pyramidal neurons exhibit a downregulation of GABA(A) receptor (GABA(A)R)-mediated inhibition that was reversed by CaN inhibitors. CaN activation appears to be dependent on seizure-induced activation of Ca2+-permeable AMPA receptors (AMPARs), because the upregulation of CaN activation and GABA(A)R inhibition were attenuated by GYKI 52466 [1-(4-aminophenyl)-4-methyl-7,8-methylenedioxy-5H-2,3-benzodiazepine hydrochloride] or Joro spider toxin. GABA(A)R beta2/3 subunit protein was dephosphorylated at 1 h after seizures, suggesting this subunit as a possible substrate of CaN in this model. Finally, in vivo administration of the CaN inhibitor FK-506 significantly suppressed hypoxic seizures, and posttreatment with NBQX (2,3-dihydroxy-6-nitro-7-sulfonyl-benzo[f]quinoxaline) or FK-506 blocked the hypoxic seizure-induced increase in CaN expression. These data suggest that Ca2+-permeable AMPARs and CaN regulate inhibitory synaptic transmission in a novel plasticity pathway that may play a role in epileptogenesis in the immature brain.
AuthorsRussell M Sanchez, Weimin Dai, Rachel E Levada, Jocelyn J Lippman, Frances E Jensen
JournalThe Journal of neuroscience : the official journal of the Society for Neuroscience (J Neurosci) Vol. 25 Issue 13 Pg. 3442-51 (Mar 30 2005) ISSN: 1529-2401 [Electronic] United States
PMID15800199 (Publication Type: Comparative Study, Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)
Chemical References
  • Excitatory Amino Acid Antagonists
  • Receptors, AMPA
  • Receptors, GABA-A
  • gamma-Aminobutyric Acid
  • 6-Cyano-7-nitroquinoxaline-2,3-dione
  • Calcineurin
  • Tacrolimus
Topics
  • 6-Cyano-7-nitroquinoxaline-2,3-dione (pharmacology)
  • Animals
  • Animals, Newborn
  • Blotting, Western (methods)
  • Calcineurin (physiology)
  • Dose-Response Relationship, Radiation
  • Electric Stimulation (methods)
  • Excitatory Amino Acid Antagonists (pharmacology)
  • Excitatory Postsynaptic Potentials (drug effects, physiology, radiation effects)
  • Gene Expression Regulation, Developmental (drug effects, physiology)
  • Hippocampus (growth & development, pathology, physiopathology)
  • Hypoxia (complications)
  • Immunoprecipitation (methods)
  • In Vitro Techniques
  • Neural Inhibition (drug effects, physiology, radiation effects)
  • Patch-Clamp Techniques (methods)
  • Rats
  • Receptors, AMPA (physiology)
  • Receptors, GABA-A (metabolism)
  • Seizures (etiology, metabolism, physiopathology)
  • Synapses (metabolism)
  • Synaptic Transmission (physiology)
  • Tacrolimus (pharmacology)
  • Time Factors
  • gamma-Aminobutyric Acid (metabolism)

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