A single packet of transmitter does not saturate postsynaptic glutamate receptors.
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.
Ishikawa
Taro
T
Department of Neurophysiology, University of Tokyo Graduate School of Medicine, 113-0033, Japan.
Sahara
Yoshinori
Y
Takahashi
Tomoyuki
T
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
D018091:Receptors, AMPA; D017470:Receptors, Glutamate; D016194:Receptors, N-Methyl-D-Aspartate; D018698:Glutamic Acid