Depressed responses of facilitatory synapses

J Neurophysiol. 2005 Jul;94(1):865-70. doi: 10.1152/jn.00689.2004. Epub 2005 Feb 23.


We show that when temporal summation takes place, depression of postsynaptic responses may ensue when the underlying synaptic conductance change is constant or even facilitatory. We term this phenomenon "apparent depression." Such apparent depression is most notable for slow synaptic conductance changes, for high frequency, and when the synapse is located at distal dendritic sites. We show that, when temporal summation ensues, the erroneous estimation of short-term synaptic plasticity arises partially from the conventional measurement of synaptic dynamics at postsynaptic potential peak time. This can be corrected when measuring overlapping synaptic responses at fixed intervals after stimulus time. Somatic voltage clamp also helps to partially correct for the apparent depression, but a good model of the neuron can do even better in providing a more accurate view of the underlying synaptic conductances.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Action Potentials / physiology
  • Action Potentials / radiation effects
  • Animals
  • Computer Simulation
  • Electric Stimulation / methods
  • Excitatory Postsynaptic Potentials / physiology
  • Excitatory Postsynaptic Potentials / radiation effects
  • Humans
  • Models, Neurological*
  • Neural Inhibition / physiology*
  • Neuronal Plasticity / physiology
  • Neuronal Plasticity / radiation effects
  • Reference Values
  • Synapses / physiology*
  • Synaptic Transmission / physiology*
  • Time Factors