Adaptation of Ca(2+)-triggered exocytosis in presynaptic terminals

Neuron. 1996 Sep;17(3):501-12. doi: 10.1016/s0896-6273(00)80182-8.


Rapid increases in Ca2+ concentration, produced by photolysis of caged Ca2+, triggered exocytosis in squid nerve terminals. This exocytosis was transient in nature, decaying with a time constant of approximately 30 ms. The decay could not be explained by a decline in presynaptic Ca2+ concentration, depletion of synaptic vesicles, or desensitization of postsynaptic receptors. Experiments in which Ca2+ was increased either in a series of steps or continuously at different rates suggested that the decay is caused by adaptation of the exocytotic Ca2+ receptor to higher levels of Ca2+. This adjustable sensitivity to Ca2+ represents a novel property of the triggering mechanism that can be used to evaluate molecular models of exocytosis. Adaptation can limit the amount of transmitter released by a nerve terminal and permit the speed of a presynaptic Ca2+ rise to serve as a critical determinant of synaptic efficacy.

Publication types

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

MeSH terms

  • Adaptation, Physiological / physiology
  • Animals
  • Calcium / metabolism*
  • Decapodiformes
  • Electrophysiology
  • Exocytosis / physiology*
  • Membrane Potentials / physiology
  • Neurotransmitter Agents / metabolism
  • Presynaptic Terminals / physiology*
  • Sensitivity and Specificity
  • Synaptic Vesicles / physiology
  • Time Factors


  • Neurotransmitter Agents
  • Calcium