Hippocampal slices from kindled rats show an increased sensitivity for induction of epileptiform activity by changes in extracellular ion concentrations.
The ability of increases in extracellular potassium ([K+]o) and/or decreases in extracellular calcium ([Ca2+]o) to induce epileptiform activity in hippocampal slices was studied by systematically varying [K+]o and [Ca2+]o. Slices prepared from kindled rats, both 1 week and 1 month after the last kindled seizure, showed an increased sensitivity to perturbations of both ions. Stimulus-locked epileptiform discharges occurred with small displacements of [K+]o and/or [Ca2+]o. The ionic threshold for spontaneous epileptiform discharges was not significantly affected. This long-lasting change in sensitivity to the ionic environment produced by the kindling process had important implications for epileptogenesis in chronically epileptic tissue.
Stringer
J L
JL
Department of Neurology, University of Virginia Medical Center, Charlottesville 22908.
Lothman
E W
EW
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002118:Calcium / Q000494:pharmacology / Q000502:physiology*; D004558:Electric Stimulation; D004827:Epilepsy / Q000378:metabolism / Q000503:physiopathology*; D006624:Hippocampus / Q000378:metabolism / Q000503:physiopathology*; D066298:In Vitro Techniques; D007696:Kindling, Neurologic; D008297:Male; D011188:Potassium / Q000494:pharmacology / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains
D011188:Potassium; D002118:Calcium