Quantal release of glutamate generates pure kainate and mixed AMPA/kainate EPSCs in hippocampal neurons.
The relative contribution of kainate receptors to ongoing glutamatergic activity is at present unknown. We report the presence of spontaneous, miniature, and minimal stimulation-evoked excitatory postsynaptic currents (EPSCs) that are mediated solely by kainate receptors (EPSC(kainate)) or by both AMPA and kainate receptors (EPSC(AMPA/kainate)). EPSC(kainate) and EPSC(AMPA/kainate) are selectively enriched in CA1 interneurons and mossy fibers synapses of CA3 pyramidal neurons, respectively. In CA1 interneurons, the decay time constant of EPSC(kainate) (circa 10 ms) is comparable to values obtained in heterologous expression systems. In both hippocampal neurons, the quantal release of glutamate generates kainate receptor-mediated EPSCs that provide as much as half of the total glutamatergic current. Kainate receptors are, therefore, key players of the ongoing glutamatergic transmission in the hippocampus.
Cossart
Rosa
R
INMED-INSERM U.29 and Université de La Méditerranée, Parc scientifique de Luminy, BP 13, 13273 Marseille Cedex 9, France.
Epsztein
Jérôme
J
Tyzio
Roman
R
Becq
Hélène
H
Hirsch
June
J
Ben-Ari
Yehezkel
Y
Crépel
Valérie
V
D000818:Animals; D004399:Dynorphins / Q000378:metabolism; D004558:Electric Stimulation; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology*; D018756:GABA Antagonists / Q000494:pharmacology; D018698:Glutamic Acid / Q000378:metabolism*; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007395:Interneurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D007700:Kinetics; D008297:Male; D019599:Mossy Fibers, Hippocampal / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D009924:Organ Culture Techniques; D017729:Presynaptic Terminals / Q000187:drug effects / Q000378:metabolism*; D017966:Pyramidal Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D018091:Receptors, AMPA / Q000037:antagonists & inhibitors / Q000378:metabolism*; D018092:Kainic Acid Receptors / Q000037:antagonists & inhibitors / Q000378:metabolism*; D026941:Sodium Channel Blockers / Q000494:pharmacology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D013572:Synaptic Vesicles / Q000187:drug effects / Q000378:metabolism*
D004399:Dynorphins; D018691:Excitatory Amino Acid Antagonists; D018756:GABA Antagonists; D018698:Glutamic Acid; D018091:Receptors, AMPA; D018092:Kainic Acid Receptors; D026941:Sodium Channel Blockers