Profoundly different calcium permeation and blockage determine the specific function of distinct cyclic nucleotide-gated channels

Neuron. 1995 Jul;15(1):169-79. doi: 10.1016/0896-6273(95)90074-8.


Sensory transduction in vertebrate photoreceptors and olfactory sensory neurons is mediated by cyclic nucleotide-gated (CNG) channels that conduct mono- and divalent cations. Ca2+ entering the cell through CNG channels intimately controls signaling pathways by regulating several key enzymes. Cloned CNG channels from photoreceptors and olfactory sensory neurons profoundly differ in their relative Ca2+ permeability, their blockage by external divalent cations, and the fraction of current carried by Ca2+. In particular, CNG channels from cone photoreceptors conduct significantly more Ca2+ than those from rod photoreceptors. Furthermore, the current through the olfactory CNG channel is entirely carried by Ca2+ at approximately 3 mM extracellular Ca2+. These results suggest that a major function of CNG channels is to provide a pathway for Ca2+ entry.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium / metabolism*
  • Calcium / pharmacology
  • Calcium Channel Blockers / pharmacology
  • Cattle
  • Cell Membrane Permeability / physiology
  • Cyclic Nucleotide-Gated Cation Channels
  • Ion Channel Gating / physiology*
  • Ion Channels / antagonists & inhibitors
  • Ion Channels / metabolism*
  • Magnesium / pharmacology
  • Nucleotides, Cyclic / metabolism*
  • Patch-Clamp Techniques
  • Retinal Rod Photoreceptor Cells / ultrastructure
  • Xenopus


  • Calcium Channel Blockers
  • Cyclic Nucleotide-Gated Cation Channels
  • Ion Channels
  • Nucleotides, Cyclic
  • Magnesium
  • Calcium