Properties of a delayed rectifier potassium current in dentate granule cells isolated from the hippocampus of patients with chronic temporal lobe epilepsy

Epilepsia. 1996 Sep;37(9):892-901. doi: 10.1111/j.1528-1157.1996.tb00043.x.


Purpose: Properties of potassium outward currents were investigated in human hippocampal dentate gyrus granule cells from 11 hippocampal specimens obtained from patients with temporal lobe epilepsy (TLE) during resective surgery.

Methods: Dentate granule cells were isolated enzymatically and outward currents analyzed by using the whole-cell configuration of the patch-clamp method. Hippocampal specimens were classified neuropathologically with respect to severe segmental cell loss, gliosis, and axonal sprouting (Ammon's horn sclerosis, AHS), or the presence of a focal lesion in the adjacent temporal lobe.

Results: A delayed rectifier outward current (IK), but not an A-type potassium current (IA) or inwardly rectifying potassium currents, was observed in all cells. The average current density of IK, the time-dependent decay of IK, and the resting membrane characteristics were not significantly different between patients with and without AHS. The voltage of half-maximal activation V1/2(act) was 5.4 +/- 1.8 mV in AHS compared with -2.9 +/- 1.8 mV in lesion-associated epilepsy (NS). In contrast, V1/2(inact) was shifted in a hyperpolarizing direction in AHS (-67.7 +/- 0.6 mV) compared with that in hippocampi not showing AHS (-47.7 +/- 2.6 mV; p = 0.0017).

Conclusions: The altered steady-state voltage-dependence of IK may result in abnormal excitability of dentate granule cells in AHS and exert a marked influence on input-output properties of the dentate gyrus.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Age of Onset
  • Brain Diseases / physiopathology
  • Cell Separation
  • Dentate Gyrus / cytology*
  • Dentate Gyrus / physiopathology
  • Epilepsy, Temporal Lobe / physiopathology*
  • Hippocampus / cytology*
  • Hippocampus / physiopathology
  • Humans
  • Membrane Potentials / physiology
  • Middle Aged
  • Neural Conduction / physiology
  • Neural Pathways / physiology*
  • Neurons / physiology*
  • Patch-Clamp Techniques
  • Potassium / physiology*
  • Sclerosis / physiopathology


  • Potassium