Nonsaturation of AMPA and NMDA receptors at hippocampal synapses.
An important issue in synaptic physiology is the extent to which postsynaptic receptors are saturated by the neurotransmitter released from a single synaptic vesicle. Although the bulk of evidence supports receptor saturation, recent studies have started to reveal that alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) and N-methyl-D-aspartate (NMDA) receptors may not be saturated by a single vesicle of glutamate. Here, we address this question through a study of putative single synapses, made by hippocampal neurons in culture, that are identified by FM1-43 staining. An analysis of the sources of variability in the amplitudes of miniature excitatory postsynaptic currents at single synapses reveals that this variability must arise presynaptically, from variations in the quantity of agonist released. Thus, glutamate receptors at hippocampal synapses are not generally saturated by quantal release.
McAllister
A K
AK
Howard Hughes Medical Institute, The Salk Institute, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA. kmcallister@ucdavis.edu
Stevens
C F
CF
D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000818:Animals; D001667:Binding, Competitive; D002478:Cells, Cultured; D016291:Dizocilpine Maleate / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018698:Glutamic Acid / Q000494:pharmacology*; D007478:Iontophoresis; D016202:N-Methylaspartate / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D017966:Pyramidal Cells / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D018091:Receptors, AMPA / Q000187:drug effects / Q000378:metabolism*; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects / Q000378:metabolism*; D013569:Synapses / Q000378:metabolism*; D009435:Synaptic Transmission
D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D018091:Receptors, AMPA; D016194:Receptors, N-Methyl-D-Aspartate; D018698:Glutamic Acid; D016202:N-Methylaspartate; D016291:Dizocilpine Maleate; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione