Subthreshold synaptic activation of voltage-gated Ca2+ channels mediates a localized Ca2+ influx into the dendrites of hippocampal pyramidal neurons

J Neurophysiol. 1995 Sep;74(3):1335-42. doi: 10.1152/jn.1995.74.3.1335.


1. Whole cell recordings and high-speed fluorescence imaging were used to investigate the spatial and temporal characteristics of Ca2+ influx during synaptic activity in hippocampal CA1 pyramidal neurons. Brief, subthreshold trains of synaptic potentials elicited by Schaffer collateral stimulation produced transient increases in [Ca2+]i in the apical dendrites near the site of synaptic input. The rises in [Ca2+]i were not due to Ca2+ entry through N-methyl-D-aspartate (NMDA)-activated or non-NMDA-activated glutamate channels, but were reduced by low concentrations of Ni2+. Hyperpolarizing prepulses caused an increase in the synaptically evoked Ca2+ transients, whereas strong hyperpolarization during the train prevented the rise in [Ca2+]i. The data suggest that subthreshold synaptic activity can open low-voltage-activated (T-type) Ca2+ channels and produce a local increase in intradendritic [Ca2+]. Such local increases in [Ca2+]i may be important for modulating the strength of synaptic connections.

Publication types

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

MeSH terms

  • Animals
  • Calcium / metabolism*
  • Calcium Channels / physiology*
  • Dendrites / physiology*
  • Fluorescence
  • Hippocampus / physiology*
  • Patch-Clamp Techniques
  • Pyramidal Cells / physiology
  • Rats
  • Rats, Sprague-Dawley
  • Synaptic Transmission / physiology


  • Calcium Channels
  • Calcium