Intrinsic excitability, synaptic potentials, and short-term plasticity in human epileptic neocortex.
Although studies of epileptic human hippocampus suggest changes of synaptic and intrinsic excitability, few changes, save the appearance of spontaneous field/synaptic potentials, are known in epileptic neocortical tissue. However, invasive EEG and histological studies suggest that neocortical tissue, even in mesial temporal lobe epilepsy, can play an important role as an irritative zone or extrahippocampal focus. We hypothesized that intrinsic neuronal and synaptic excitability, as well as short-term plasticity, are altered in neocortical areas, particularly with elevated K+ levels as occur during seizures. We analyzed neuronal firing properties, synaptic responses, and paired-pulse plasticity in human neocortical slices from tissue resected during epilepsy surgery, both under normal and under pathological conditions, i.e., after elevating K+ (4/8 mM), with rat neocortical slices as controls. Neuronal firing properties were not different. We did find, however, alterations of synaptic responsiveness in epileptic tissue, i.e., an elevated network excitability with K+ elevations, and reduction of paired-pulse depression.
Koch
Uwe-Robert
UR
Institute of Physiology, University of Münster, Münster, Germany.
Musshoff
Ulrich
U
Pannek
Heinz-Wolfgang
HW
Ebner
Alois
A
Wolf
Peter
P
Speckmann
Erwin-Josef
EJ
Köhling
Rüdiger
R
D000328:Adult; D002908:Chronic Disease; D004828:Epilepsies, Partial / Q000503:physiopathology; D004833:Epilepsy, Temporal Lobe / Q000503:physiopathology*; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology*; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D019579:Neocortex / Q000503:physiopathology*; D009473:Neuronal Plasticity / Q000502:physiology*; D011189:Potassium Chloride / Q000494:pharmacology; D013702:Temporal Lobe / Q000503:physiopathology*
D018691:Excitatory Amino Acid Antagonists; D011189:Potassium Chloride