Reduced sodium current in GABAergic interneurons in a mouse model of severe myoclonic epilepsy in infancy

Nat Neurosci. 2006 Sep;9(9):1142-9. doi: 10.1038/nn1754. Epub 2006 Aug 20.

Abstract

Voltage-gated sodium channels (Na(V)) are critical for initiation of action potentials. Heterozygous loss-of-function mutations in Na(V)1.1 channels cause severe myoclonic epilepsy in infancy (SMEI). Homozygous null Scn1a-/- mice developed ataxia and died on postnatal day (P) 15 but could be sustained to P17.5 with manual feeding. Heterozygous Scn1a+/- mice had spontaneous seizures and sporadic deaths beginning after P21, with a notable dependence on genetic background. Loss of Na(V)1.1 did not change voltage-dependent activation or inactivation of sodium channels in hippocampal neurons. The sodium current density was, however, substantially reduced in inhibitory interneurons of Scn1a+/- and Scn1a-/- mice but not in their excitatory pyramidal neurons. An immunocytochemical survey also showed a specific upregulation of Na(V)1.3 channels in a subset of hippocampal interneurons. Our results indicate that reduced sodium currents in GABAergic inhibitory interneurons in Scn1a+/- heterozygotes may cause the hyperexcitability that leads to epilepsy in patients with SMEI.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Action Potentials / physiology*
  • Animals
  • Cell Line
  • Disease Models, Animal
  • Electroencephalography
  • Epilepsies, Myoclonic / genetics
  • Epilepsies, Myoclonic / physiopathology*
  • Genotype
  • Humans
  • Immunoblotting
  • Infant
  • Interneurons / cytology
  • Interneurons / metabolism*
  • Interneurons / physiology
  • Mice
  • Mice, Inbred C57BL
  • Mice, Inbred Strains
  • Mice, Knockout
  • Mutation / genetics
  • NAV1.1 Voltage-Gated Sodium Channel
  • Nerve Tissue Proteins / genetics
  • Nerve Tissue Proteins / metabolism
  • Nerve Tissue Proteins / physiology*
  • Patch-Clamp Techniques
  • Phenotype
  • Seizures / genetics
  • Seizures / mortality
  • Seizures / physiopathology
  • Sodium Channels / genetics
  • Sodium Channels / metabolism
  • Sodium Channels / physiology*
  • Survival Rate
  • gamma-Aminobutyric Acid / metabolism

Substances

  • NAV1.1 Voltage-Gated Sodium Channel
  • Nerve Tissue Proteins
  • SCN1A protein, human
  • Scn1a protein, mouse
  • Sodium Channels
  • gamma-Aminobutyric Acid