title: A single packet of transmitter does not saturate postsynaptic glutamate receptors.
abstract: Neurotransmitter is stored in synaptic vesicles and released by exocytosis into the synaptic cleft. One of the fundamental questions in central synaptic transmission is whether a quantal packet of transmitter saturates postsynaptic receptors. To address this question, we loaded the excitatory transmitter L-glutamate via whole-cell recording pipettes into the giant nerve terminal, the calyx of Held, in rat brainstem slices. This caused marked potentiations of both quantal and action potential-evoked EPSCs mediated by alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) or N-methyl-D-aspartate (NMDA) receptors. These results directly demonstrate that neither AMPA nor NMDA receptors are saturated by a single packet of transmitter, and indicate that vesicular transmitter content is an important determinant of synaptic efficacy.
authors.affiliation: Department of Neurophysiology, University of Tokyo Graduate School of Medicine, 113-0033, Japan.
authors.forename: Taro
authors.initials: T
authors.lastname: Ishikawa
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Sahara
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Takahashi
mesh_terms: D000818:Animals; D001306:Auditory Pathways / Q000378:metabolism / Q000648:ultrastructure; D001665:Binding Sites / Q000187:drug effects / Q000502:physiology; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology*; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology*; D018698:Glutamic Acid / Q000378:metabolism* / Q000494:pharmacology; D009847:Olivary Nucleus / Q000378:metabolism / Q000648:ultrastructure; D009924:Organ Culture Techniques; D011149:Pons / Q000378:metabolism / Q000648:ultrastructure; D017729:Presynaptic Terminals / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D051381:Rats; D018091:Receptors, AMPA / Q000187:drug effects / Q000378:metabolism; D017470:Receptors, Glutamate / Q000187:drug effects / Q000378:metabolism*; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects / Q000378:metabolism; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D013572:Synaptic Vesicles / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D013696:Temperature
chemical_list: D018091:Receptors, AMPA; D017470:Receptors, Glutamate; D016194:Receptors, N-Methyl-D-Aspartate; D018698:Glutamic Acid