Cell type-specific changes in spontaneous and minimally evoked excitatory synaptic activity in hippocampal CA1 interneurons of kainate-treated rats

Epilepsy Res. 2006 Mar;68(3):241-54. doi: 10.1016/j.eplepsyres.2005.11.008. Epub 2005 Dec 20.

Abstract

The epileptiform activity in the kainic acid (KA) model of epilepsy arises from complex changes in excitation and inhibition. To assess the involvement of excitatory drive onto inhibitory interneurons in this epileptiform activity, we examined changes in spontaneous and minimally evoked excitatory post-synaptic currents (sEPSCs and eEPSCs) in CA1 interneurons in stratum oriens/alveus (O/A) and stratum radiatum (RAD) in rat hippocampal slices after KA treatment. The frequency and amplitude of sEPSCs and the amplitude of eEPSCs were unchanged in O/A interneurons, but the EPSC kinetics were significantly slower. These changes appear to be due to altered kinetics and voltage-dependent properties of the NMDA component of EPSCs in O/A interneurons. In contrast, sEPSCs and eEPSCs in RAD interneurons did not change after KA treatment. The distinct changes in excitatory synaptic activity in interneurons differentially involved in feedback (O/A) versus feedforward (RAD) inhibition suggest a cell type-specific reorganization of excitatory synapses after KA treatment. These modifications in excitatory input to interneurons could contribute to the maintenance of inhibition of CA1 pyramidal cells after KA treatment, or may also create network conditions favourable to epileptiform activity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Convulsants
  • Disease Models, Animal
  • Excitatory Postsynaptic Potentials / physiology*
  • Hippocampus / physiopathology*
  • Interneurons / physiology*
  • Kainic Acid
  • Kindling, Neurologic
  • Male
  • Pyramidal Cells / physiology
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, N-Methyl-D-Aspartate / physiology
  • Seizures / chemically induced
  • Seizures / physiopathology*

Substances

  • Convulsants
  • Receptors, N-Methyl-D-Aspartate
  • Kainic Acid