Altered balance between excitatory and inhibitory inputs onto CA1 pyramidal neurons from SV2A-deficient but not SV2B-deficient mice

J Neurosci Res. 2012 Dec;90(12):2317-27. doi: 10.1002/jnr.23111. Epub 2012 Jul 30.


Synaptic vesicle protein 2 (SV2) is a glycoprotein that exists in three isoforms, SV2A, SV2B, and SV2C. SV2A knockout (KO) mice and SV2A/SV2B double KO (DKO) mice, but not SV2B KO animals, start to experience severe seizures and weight loss 7 days after birth and die at about postnatal day (P)14-P23. Because excitatory and inhibitory inputs play a major role in controlling neuronal excitability in the hippocampus, we examined the effects of SV2A and/or SV2B deletions on glutamatergic and GABA(A) neurotransmission in hippocampal CA1 pyramidal neurons. Spontaneous and miniature excitatory and inhibitory postsynaptic currents (sEPSCs, mEPSCs, sIPSCs, and mIPSCs, respectively) were recorded using the whole-cell patch-clamp technique in slices from P6-P14 mice. The frequency of sEPSCs was increased in SV2A KO and SV2A/SV2B DKO mice, but their amplitude was unchanged. Such changes were not observed in SV2B KOs. On the contrary, the frequency and amplitude of sIPSCs were decreased in SV2A KO and SV2A/SV2B DKO mice but not in SV2B KO animals, as reported previously for the CA3 region. Kinetic parameters of sIPSCs and sEPSCs were unchanged. Importantly, no changes were observed in any genotype when examining mEPSCs and mIPSCs. We conclude that action potential- and Ca(2+) -dependent glutamatergic and GABAergic synaptic transmission are differentially altered in the hippocampus of SV2A-deficient mice, whereas the mechanism of exocytosis itself is not changed. The altered balance between these major excitatory and inhibitory inputs is probably a contributing factor to seizures in SV2A KO and SV2A/SV2B DKO mice.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Action Potentials
  • Animals
  • CA1 Region, Hippocampal / cytology*
  • Calcium Signaling
  • Excitatory Postsynaptic Potentials / physiology*
  • Genes, Lethal
  • Glutamic Acid / physiology
  • Inhibitory Postsynaptic Potentials / physiology*
  • Membrane Glycoproteins / deficiency*
  • Membrane Glycoproteins / genetics
  • Membrane Glycoproteins / physiology
  • Mice
  • Mice, Knockout
  • Mice, Transgenic
  • Nerve Tissue Proteins / deficiency*
  • Nerve Tissue Proteins / genetics
  • Nerve Tissue Proteins / physiology
  • Patch-Clamp Techniques
  • Protein Isoforms / physiology
  • Pyramidal Cells / physiology*
  • Synaptic Vesicles / metabolism


  • Membrane Glycoproteins
  • Nerve Tissue Proteins
  • Protein Isoforms
  • Sv2a protein, mouse
  • Sv2b protein, mouse
  • Glutamic Acid