A brief period of epileptiform activity strengthens excitatory synapses in the rat hippocampus in vitro.
OBJECTIVE
We examined here whether a very short period of epileptiform activity could produce lasting modifications of synaptic strength and network properties in the rat hippocampus in vitro.


METHODS
Synaptic transmission at CA3-CA1 and at CA3-CA3 pyramidal cell synapses was monitored in hippocampal slice cultures before and after a very brief episode of epileptiform activity (20-180 s) induced with bicuculline methochloride.


RESULTS
We show here that a brief period of epileptiform activity induces long-lasting potentiation of glutamatergic transmission at CA3-CA1 and at CA3-CA3 pyramidal cell synapses. This potentiation also was observed at synapses formed by pairs of monosynaptically connected neurons. It was dependent on N-methyl-d-aspartate (NMDA) receptors, occluded classic long-term potentiation, and could be depotentiated by low-frequency stimulation at 3 Hz. Recruitment of polysynaptic pathways within area CA3 was facilitated after epileptiform activity indicating that the induced potentiation enhanced overall hippocampal network excitability.


CONCLUSIONS
These changes in synaptic transmission may contribute to the genesis of epilepsy and to seizure-associated memory deficits.
Debanne
Dominique
D
Brain Research Institute, University of Zurich, Zürich, Switzerland. debanne.d@jean-roche.univ-mrs.fr
Thompson
Scott M
SM
Gähwiler
Beat H
BH
D000818:Animals; D001640:Bicuculline / Q000031:analogs & derivatives / Q000494:pharmacology; D002478:Cells, Cultured; D004195:Disease Models, Animal; D004558:Electric Stimulation; D004827:Epilepsy / Q000139:chemically induced / Q000378:metabolism / Q000503:physiopathology*; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D018756:GABA Antagonists / Q000494:pharmacology; D006624:Hippocampus / Q000378:metabolism / Q000503:physiopathology*; D006801:Humans; D066298:In Vitro Techniques; D007395:Interneurons / Q000187:drug effects / Q000502:physiology; D017774:Long-Term Potentiation / Q000187:drug effects / Q000502:physiology; D008569:Memory Disorders / Q000503:physiopathology; D017966:Pyramidal Cells / Q000378:metabolism / Q000502:physiology; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects / Q000502:physiology; D009435:Synaptic Transmission / Q000502:physiology*
D018756:GABA Antagonists; D016194:Receptors, N-Methyl-D-Aspartate; C006749:bicuculline methochloride; D001640:Bicuculline