Nonuniform distribution of Ca2+ channel subtypes on presynaptic terminals of excitatory synapses in hippocampal cultures

J Neurosci. 1997 Apr 15;17(8):2738-45. doi: 10.1523/JNEUROSCI.17-08-02738.1997.


Several subtypes of Ca2+ channel support the release of glutamate at excitatory synapses. We investigated the pattern of colocalization of these subtypes on presynaptic terminals in hippocampal cultures. N-type (conotoxin GVIA-sensitive) or P/Q-type (agatoxin IVA-sensitive) Ca2+ channels were blocked selectively, and the reduction in transmitter release probability (Pr) was measured with MK-801. The antagonists completely blocked release at some terminals, reduced Pr at others, and failed to affect the remainder. In contrast, nonselective reduction of presynaptic Ca2+ influx by adding Cd2+ or lowering external Ca2+ reduced Pr uniformly at all terminals. We conclude from these results that the mixture of N-type and P/Q-type channels varies markedly between terminals on the same afferent. The distribution of Ca2+ channel subtypes was the same for high and low Pr terminals. Given that Ca2+ channel subtypes are affected differentially by neuromodulators, these findings lead to the possibility of terminal-specific modulation of synaptic function.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium Channel Blockers / pharmacology
  • Calcium Channels / classification*
  • Calcium Channels / drug effects
  • Calcium Channels / physiology*
  • Cells, Cultured
  • Dizocilpine Maleate / pharmacology
  • Evoked Potentials / drug effects
  • Hippocampus / physiology*
  • Kinetics
  • Models, Neurological
  • N-Methylaspartate / pharmacology
  • Neurons / physiology*
  • Peptides / pharmacology
  • Presynaptic Terminals / drug effects
  • Presynaptic Terminals / physiology*
  • Spider Venoms / pharmacology
  • Synapses / drug effects
  • Synapses / physiology*
  • omega-Agatoxin IVA
  • omega-Conotoxin GVIA


  • Calcium Channel Blockers
  • Calcium Channels
  • Peptides
  • Spider Venoms
  • omega-Agatoxin IVA
  • N-Methylaspartate
  • Dizocilpine Maleate
  • omega-Conotoxin GVIA