Attenuated plasticity of postsynaptic kainate receptors in hippocampal CA3 pyramidal neurons.
Kainate receptor-mediated components of postsynaptic currents at hippocampal mossy fiber synapses have markedly slower kinetics than currents arising from AMPA receptors. Here, we demonstrate that other aspects of kainate and AMPA receptor function at this synapse are distinct; in particular, kainate receptor currents are less sensitive to short- and long-term increases in presynaptic strength. EPSCs arising predominantly from AMPA receptors exhibited well characterized paired-pulse facilitation, frequency facilitation, and NMDA receptor-independent long-term potentiation, whereas isolated kainate receptor synaptic currents (KA-EPSCs) exhibited attenuated facilitation and long-term potentiation. In addition, KA-EPSCs varied in their sensitivity to a low-affinity competitive antagonist, suggestive of a synaptic heterogeneity greater than that of EPSCs comprised predominantly of AMPA receptors. These data suggest that the proportional contribution of AMPA and kainate receptors to ensemble synaptic currents will vary depending on the firing frequency of mossy fiber afferents. These synaptic features may be a mechanism for limiting activation of kainate receptors at mossy fiber synapses, which has been shown to be involved in seizurogenic firing of the CA3 network.
Ito
Koichi
K
Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, Texas 77555-1031, USA.
Contractor
Anis
A
Swanson
Geoffrey T
GT
D000818:Animals; D004558:Electric Stimulation / Q000379:methods; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D017774:Long-Term Potentiation / Q000187:drug effects / Q000502:physiology; D051379:Mice; D019599:Mossy Fibers, Hippocampal / Q000187:drug effects / Q000502:physiology; D009473:Neuronal Plasticity / Q000502:physiology*; D018408:Patch-Clamp Techniques; D017966:Pyramidal Cells / Q000187:drug effects / Q000378:metabolism*; D018091:Receptors, AMPA / Q000037:antagonists & inhibitors / Q000378:metabolism; D018092:Kainic Acid Receptors / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors; D013569:Synapses / Q000378:metabolism*
D018691:Excitatory Amino Acid Antagonists; D018091:Receptors, AMPA; D018092:Kainic Acid Receptors; D016194:Receptors, N-Methyl-D-Aspartate