Fast kinetics of exocytosis revealed by simultaneous measurements of presynaptic capacitance and postsynaptic currents at a central synapse

Neuron. 2001 Apr;30(1):171-82. doi: 10.1016/s0896-6273(01)00271-9.

Abstract

The rate of release from nerve terminals depends on both the number of release sites and the rate of release at each site. The latter remains largely unknown at central synapses. We addressed this issue by simultaneously measuring the nerve terminal membrane capacitance and the postsynaptic current at single calyceal synapses in rat brainstem. We found that a 10 ms presynaptic step depolarization depleted a releasable pool containing 3300-5200 vesicles. Released vesicles were endocytosed with a time constant of a few seconds to tens of seconds. Release of only one third of this pool saturated both postsynaptic AMPA and NMDA receptors. A release site can release more than three vesicles in 10 ms (>300 vesicles per second). We conclude that both a large number of release sites and a fast release rate at each site enable synapses to release at a high rate.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Auditory Pathways / cytology
  • Auditory Pathways / metabolism
  • Calcium Signaling / physiology
  • Central Nervous System / drug effects
  • Central Nervous System / metabolism*
  • Endocytosis / physiology
  • Excitatory Amino Acid Antagonists / pharmacology
  • Excitatory Postsynaptic Potentials / drug effects
  • Excitatory Postsynaptic Potentials / physiology
  • Exocytosis / drug effects
  • Exocytosis / physiology*
  • Glutamic Acid / metabolism
  • Ion Channels / drug effects
  • Ion Channels / metabolism*
  • Kinetics
  • Kynurenic Acid / pharmacology
  • Membrane Potentials / drug effects
  • Membrane Potentials / physiology*
  • Pons / cytology
  • Pons / metabolism
  • Presynaptic Terminals / drug effects
  • Presynaptic Terminals / metabolism*
  • Rats
  • Rats, Wistar
  • Receptors, Glutamate / drug effects
  • Receptors, Glutamate / metabolism
  • Synaptic Membranes / drug effects
  • Synaptic Membranes / metabolism*
  • Synaptic Transmission / drug effects
  • Synaptic Transmission / physiology
  • Synaptic Vesicles / drug effects
  • Synaptic Vesicles / metabolism*

Substances

  • Excitatory Amino Acid Antagonists
  • Ion Channels
  • Receptors, Glutamate
  • Glutamic Acid
  • Kynurenic Acid